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Weed: A Gateway Drug Across Generations?

If you haven’t seen marijuana in the news lately then you haven’t been paying attention. This week lawmakers in Maryland, Maine, Massachusetts, Colorado, WashingtonKentucky, and Georgia are all talking about weed. Some doctors are using the drug to treat epilepsymultiple sclerosis, and chronic pain. Journalists are finding stories of marijuana lobbyists and marijuana job fairs and multi-day cannabis tours.

Most of these news stories mention that little is known about the long-term effects of marijuana use. But I bet the average Joe is much more likely to make jokes about weed than fret about its potential harms. I was in the joking camp last week. My perspective is beginning to shift, however, thanks to a new rat study suggesting that steady marijuana exposure causes brain and behavioral problems not only in the animals exposed, but in their future ratlets.

“When I was in school you were taught that the only thing you pass on to your kids is your DNA sequence. Now we know that what you do in your lifetime impacts the next generation more than we thought,” says lead investigator Yasmin Hurd, a neuroscientist at the Mount Sinai School of Medicine in New York. “It’s important for people to think about that as we have these public discussions about marijuana.”

Marijuana is the most commonly used illicit drug in the United States, and seems to be getting more popular by the day. An estimated 18.9 million people have used it sometime in the past month, according to a 2012 survey done by the U.S. Department of Health and Human Services. That’s up from 14.5 million in 2007. As more people use it, more people seem to think it’s safe. That same survey showed that, in 2007, 55 percent of kids between 12 and 17 perceived “great risk” in smoking pot. In 2012, only 44 percent did.

But just how risky is it? Scientists are only beginning to figure that out.

Several years ago, Hurd and her colleagues showed that adolescent rats exposed to THC (the molecule primarily responsible for pot’s mind-altering effects) are more likely to self-administer heroin as adults than are rats not exposed to THC. This pointed to weed as a “gateway” into other kinds of addictive drugs.

The new study aimed to see whether any of these effects carried into the next generation. Over the past decade or so, many researchers have reported that a wide variety of environmental exposures leave chemical marks on DNA that stick around in the germ line, sometimes for several generations. (I just wrote a feature for Nature about this avenue of research.) To give one well-known example, a 2002 study of Swedish historical records found that men who had experienced famine in childhood were less likely to have grandsons with heart disease or diabetes than those who were well fed.

Just as they did in previous studies, Hurd’s team gave male and female rats periodic injections of THC throughout their adolescent period. This pattern of exposure is meant to mimic the typical pot-smoking teen. “Every few days they got about a joint’s worth of THC,” Hurd says.

Several weeks after the exposure ends (enough time for all traces of THC to disappear), the researchers allowed the animals to mate. Immediately after delivery, their pups were transferred to another cage to be raised by a female rat who had never been exposed to THC.

When those babies reached adulthood, even though they themselves had never been exposed to THC, their brains showed a range of molecular abnormalities. They had unusually low expression of the receptors for glutamate and dopamine, two important chemical messengers, in the striatum, a brain region involved in compulsive behaviors and the reward system. What’s more, brain cells in this region had abnormal firing patterns, the study found.

“I really didn’t expect such significant differences,” Hurd says. “The fact that you see significant changes, molecular changes, in how the neurons communicate with each other — that’s very significant to me.”

This second generation had altered behaviors as well. Compared with controls, rats whose parents had been exposed to THC were more sensitive to novelty in their environment and were more likely to self-administer heroin by repeatedly pressing a lever. All of this would suggest, as the authors wrote in the paper, that marijuana has a “cross-generational gateway” effect.

“It’s always important to recognize that animal models are just that, and not always perfect predictors of human behavior. That said, these data are striking,” says Chris Pierce, a neuroscientist at the University of Pennsylvania, who was not involved in the new study. Last year Pierce’s team reported a similar kind of epigenetic inheritance: Male offspring of rats that had been exposed to cocaine showed increased resistance to cocaine addiction compared with controls.

As is true of so many epigenetic studies, the researchers don’t know much about the biological mechanism that might allow THC exposure to carry over to the next generation. Pierce points out that because both the mother and father were exposed to THC, it’s unclear whether one or both parents must be exposed in order for the offspring to be affected.

Hurd’s team is now analyzing the sperm of the exposed males to see whether it carries abnormal patterns of DNA methylation, a common epigenetic marker. The researchers also also investigating whether some of these effects extend to a third generation.

Epigenetic influences may seem scary — it’s awful to think that dumb choices I made in college might one day mess up my kid’s brain. But Hurd puts a more optimistic spin on it. Just as drug exposures can leave harmful marks on the genome, our other experiences or behaviors may be able to undo the damage, or have other positive effects. “Some things could counter it, and others could exacerbate it,” she says. “We don’t appreciate this plasticity enough.”

This kind of scientific research, in Hurd’s views, too often gets left out of the public debate over the legalization of marijuana. “If anyone brings any science into the discussion you’re seen as this negative group trying to stop the freedom of individuals, and that’s not the case,” she says. “I think we need to have the debate, with science being a huge part of that.”

198 thoughts on “Weed: A Gateway Drug Across Generations?

  1. When you read any study showing possible harm from marijuana use have you ever wondered why all the summaries use terms like “possibly linked with” or “could result in”??
    If you look a little further into the study and find the source of funding you will find that it was paid for by the US government or one of it’s bureaucratic arms.
    If you accept could be linked with as scientific proof there is no need to talk to you about it but if you want truth look to history,,mankind covered the earth and started the Industrial age with no age restrictions and no “low thc” industrial hemp,,,and yet mankind has walked on the moon,,,marijuana does not cause near as much brain damage as putting someone in prison for smoking a plant that makes them happy,,or the people that support the policy.

  2. All substances put into the body cause epigenetic changes. The parkinsons association recommends people with it do not eat beef and pork, as it increases the formation of beta-amyloid plaques.(which many believe are responsible for parkinsons) As for it reducing the number of glutamate receptors, that might be a good thing. Monosodium glutamate can cause all kinds of negative symptoms, including heart failure. (at high doses) Reduced dopamine receptors is not a good thing, but were there adequate controls to demonstrate that injected pure thc (which is more akin to heroin then marijuana, as it’s a highly refined product.) is the most accurate representation of what marijuana users use? There is also the fact that many prescription drugs also produce similar epigenetic changes, especially drugs that affect dopamine and serotonin directly. It seems like the best solution is to avoid all drugs, whether they are peddled as legal and safe, or sold on the street. (barring life threatening conditions of course)

    I recently met a person who had a celiac disease diagnosis, and her experience of eating flour products while traveling showed a clear correlation between countries that allow gmo’s and those that don’t. (countries that had banned gmo wheat caused her no stomach upset issues when eating bread or wheat products) Even our foods produce epigenetic changes. Hippocrates said it best, let food be thy medicine.

  3. A wholly irresponsible article. Firstly, rats and humans are not the same. You cannot educate a rat about the perils of heroin use like you can a human. Secondly, this ‘research’ was funded by an organisation that has an anti-pot agenda. Not fair, not balanced. Poor journalism.

  4. Please remove this article, terrible piece intended to scare. If your quality of life consisted of living in a lab in a box you would “self administer” heroin all day too. Besides, they are rats!

  5. Superstitions about drugs, which this article seems to perpetuate, have caused far, far more damage to people than any of the drugs in question, much less virtually harmless marijuana. The issue is beyond discussion: the well has long since been poisoned beyond cure. We need to stop the Drug War, now. Please don’t contribute to this ongoing crime against humanity.

  6. I’d like to clear something up here. I’m not for the drug war. Personally, I’m actually in favor of drug legalization. I was pretty shocked to discover, however, that because the subject is so politicized, these sorts of scientific discoveries are not talked about in the media. I’m trying to rectify that to the extent that I can.

    Just because you’re in favor of marijuana legalization doesn’t mean you should try to suppress the dissemination of sound science. Once all the evidence is on the table, then we can fully assess whether the benefits outweigh the harms. (I suspect they will, but like all claims, this needs evidence.)

  7. Unfortunately, it isn’t politically possible to conduct normal science about certain drugs, just as it isn’t possible to conduct normal science about differences in general ability based on race or ethnicity. Many thousands of important careers, and billions of dollars, are invested in the Drug War, and any attempt to modify this lucrative enterprise will be vehemently resisted. Among other things, pseudoscience will be brought to bear. It’s a reversal of the situation with the tobacco industry, which was able to fend off obvious scientific fact for generations in order to protect the use of tobacco. Our scientific establishment is not set up to bear the sort of pressures which large-scale commerce or other mass interests can impose on it. Maybe it should be, but it isn’t. When a large corporation or other important interest group is inconvenienced by scientific findings, they just go out and buy as many scientists as they need to neutralize them. Besides the tobacco wars, look at the disputes about climate.

  8. This is an interesting piece about THC-induced “potential epigenetic modification”. The article focus on THC (the main psychoactive compound of cannabis plants) but more than 400 other chemicals (phytocannabinoids: CBC, CBD, CBG….) also are in the cannabis plant. More importantly, these compounds exhibit different pharmacological properties. There is growing interest in evaluating the potential therapeutic interest of phytocannabinoids and now are subject of intensive research. In addition, for its clinical potential, several of these cannabinoids are in clinical trials (i.e. cancer, AD, PD, ALS, HD and alcohol consumption). http://www.clinicaltrials.gov/ct2/results?term=cannabinoids&Search=Search

  9. Wonderful article touching on uber-important issue of epigenetic impacts of direct germline exposures. Thank you for the excellent work. For those interested in this phenomenon please follow GermlineExposures.org.

  10. This certainly goes in the fostering fear and anxiety category. The research and reporting of the research is valid, but to single out one particular substance without comparing other substances we as a society are exposed to, is irresponsible. I agree with the quote that science needs to be a huge part of a legalization debate but where are the epigenetic studies about alcohol exposure, nicotine exposure, or excess glucose exposure so that we can make informed decisions. The other part that is missing from the science quote is that prohibition has wide-ranging social ramifications beyond the health effects or epigenetic influences of those who choose to consume substances that alter chemical systems in the body, such as the massively disproportionate incarceration rate for minorities on nonviolent possession charges.

  11. Even the ONDCP has quit using cannabis as a “gateway” drug or even claiming that marijuana is addictive,,now it is listed as causing a dependency,,a dependency is not being able to start your day without a Starbucks,,an addiction is willing to rob a Starbucks to get it.
    The gateway theory has been debunked,,if marijuana is the most popular illicit drug it stands to reason that most users would start out on marijuana,,,DUHHH.
    It is more “spin” put on a fact that means nothing,,as in “”over 460k ER room visits are “related” to marijuana use,,one of the most frequent statistics quoted that sounds as if marijuana had anything to do with the ER visit when it is info given on the entry form and has nothing to do with why the patient went to the ER,,,and marijuana,again being the #1 illicit drug it makes sense that it shows up on more ER entry forms,,,it is how the government has brainwashed people for the last 75 years,,bought science and twisted statistics that mean nothing.

  12. Okay, if you want 13 year olds to read this and run to their parents and say “DADDY DADDY THESE PEOPLE SAY POT IS BAD, ARE THEY RIGHT?” and then 12 years later this said 13 year old is suffering from severe depression, cancer, or any other terminal illness, physical or phycological, and they said “I don’t want to end up like those rats” then you yourself, should be shamed. You know whats also been proven? That marijuana helps soothe the brain when phycological twist and struggles surface. Maybe you should try it sometime.

  13. This article deals with two disparate phenomena – the notion of “the gateway effect” plus epigenetics.

    The gateway effect is said to involve cannabis use predisposing to harder drug use. This is a bit of an outdated concept and remains controversial. Here are some more nuanced articles from Dirk Hanson (http://addiction-dirkh.blogspot.ca/2013/04/marijuana-and-gateway-hypothesis.html) and Maia Szalavitz http://healthland.time.com/2010/10/29/marijuna-as-a-gateway-drug-the-myth-that-will-not-die/

    Even the article that is quoted to support “weed as a gateway” ends with the line: “None the less, the possibility remains that the association is non-causal and reflects factors that were not adequately controlled in the analysis.” Unfortunately it is this confusion between causation and coorelation that leads people to believe in the gateway effect.

    Certainly the gateway effect for marijuana has not been well established, though here are some interesting studies about alcohol (http://www.ncbi.nlm.nih.gov/pubmed/22712674) and tobacco (http://www.sciencedaily.com/releases/2013/05/130505073742.htm) as gateway drugs.

    Moving onto epigenetics, context is again important. We understand that alcohol is a direct fetal poison resulting in fetal alcohol syndrome and that both alcohol and tobacco are causes of epigenetic changes that lead to cancer within one generation, never mind offspring. http://mutage.oxfordjournals.org/content/22/2/91.full.

    Given the North American obesity epidemic, this is likely to represent far more dangerous epigenetic fall out (http://www.the-scientist.com/?articles.view/articleNo/34307/title/Fat-Dads–Epigenetic-Legacy/)

    Lastly there are the cautions that usually apply to extending research findings in rats into humans particularly in light of the Rat Park experiments

    A recent poll showed that Americans believe that tobacco, alcohol and sugar are all more harmful than marijuana (http://blogs.wsj.com/washwire/2014/03/12/wsj-poll-candy-is-dandy-but-pot-is-less-harmful/?mod=WSJBlog). I see nothing in this article to change the relative positions of these substances, so when you ask “Just how risky is it?”, the answer is likely less risky than sugar, alcohol or tobacco. In context.

  14. I agree with some of the comments that this particular test is sort of invalid. The use of one of the many chemicals found in weed in a rat is unsound. Seriously…the best test subjects would be the heavy users willing to talk to a scientist about their daily use. To delve more psychologically than through tangible tests would be a better assumption of what the drug actually does. There are apparently 18.9 million test subjects out there so why aren’t they being used? I am more surprised there are no big business lobbyists pushing for the legalization simply due to the number one fact that American loves to run on (and it’s not Dunkin)…..capitalism. There is so much potential to boost the economy in simply legalizing the one drug that apparently millions of Americans love to use.

    1. Hi southwest,

      Of course, human studies would be ideal. The trouble with studying transgenerational effects in humans, though, is it’s usually impossible to sort out biological versus social factors. If my mom smoked pot regularly in her teenage years, and then I grow up and become a heroin addict, is that because of an epigenetic change or because of something related to my interactions with her, or how I was raised? These are very thorny relationships and animal models make things a bit easier to tease apart.

  15. The problem with this article is that “if you smoke weed not only will you be more likely to use heroin but so will your children!” sounds like ridiculous scaremongering that will be rejected out of hand regardless of whether or not it’s true (for rats).

  16. thanks for this article virginia. i know you have a commitment to truth and i appreciate you writing this. please continue bringing us important science news on topics like these and others even when they may be unpopular with some.

  17. Thanks for this article, Virginia. It brings an important bit of information to light which I would not otherwise have known. This is just another piece of information I’m now able to use to inform my consumption habits, even were weed legalized in the US (I don’t think this necessarily argues against it, given the legal realities and overall ineffectiveness of the war on drugs – however that’s another issue entirely, as you’ve noted in other responses.) Please continue to provide coverage like this, even though it is likely to be controversial with readers.

  18. Well, I appreciated this article and didn’t find it offensive or “scary.” I think you made it clear that the study was about THC, what the study entailed, and how the results are being interpreted. The second I saw the headline, I knew the comments the article would provoke, which is kind of sad.

  19. http://m.jneurosci.org/content/29/47/14764.full

    “Compared with the documented effects of THC to enhance heroin self-administration (Solinas et al., 2004; Ellgren et al., 2007), the present data demonstrated that CBD specifically inhibited reinstatement of cue-induced heroin seeking.”

    Perhaps researchers will find that this effect carries over to the next generation as well.

  20. Scientists are just begining to figure out the effects? Just? thank god they came just in the nick of time. This drug JUST came out. Glad they were paying attention. This has been studied to the nines, babe. You think this is ground breaking news? Sorry, been there heard that.

  21. The possible gateway effect that concerns me most is this; that weed might lead on to tobacco. a life-long addiction that materially shortens the lifespan of one user in four, affects the unborn, and is transmitted down the generations by example.

  22. I find it interesting how pot fans may take “the negative effect of pot” type articles way too personally. Do not get me wrong, I do enjoy wine, beer and my Jack&Coke, sometimes I do it too much. I do, however, I face that it will not necessarily make me live longer. So why it is hard to imagine that pot actually may have negative effects on your body. Fellows raging on this article perhaps assume some sort of motivation behind this writing, which I do not see.

    1. Given the large number of anecdotes offered as evidence in this discussion, especially by Prohibition fans, it’s clear that there are a lot of people who don’t begin to understand scientific methods. But I suppose we knew that already.

  23. Yes Virginian there is no Santa Claus. No this does not qualify as something to add to the ‘public debate.’ Hurd is being sponsored by NIDA who has a stake in proving how bad marijuana is. The model of addiction she propagates is hardly ‘science’ rather it is a moral stand which NIDA is heavily invested in. The epigenetic information is fascinating, unfortunately you should be embarrassed by the ‘sensational’ headline (This is NG after all, not FOX) and the absolute lack of scientific credibility this highly biased and conjectured piece reveals. Rats not humans. There is no scientific consensus on the vague term ‘addiction.’ (Well there once was, but it has lost all meaning except as an excuse or a condemnation) Please consider actual ‘research’ instead of fluff pieces for paid drug warriors.

  24. There have been so many lies about the harm that MJ can do. That I just don’t believe a word from the naysayers anymore. All my friends used pot as we were growing up. Most now have great kids that have careers in everything from engineering to literature. Several have written books. Many already have family’s of their own. an most of them do not smoke themselves. So in my head I say, “Just another Bullshit Article.”

  25. On this same premise, alcohol should also be considered a gateway drug which has just as much harm, if not more on the body. Having a joint here and there isn’t the problem. It’s marijuana abuse. Just like any other kind of recreational or subscribed drug.

    With treatment, there are far worse treatments out there for illnesses than marijuana which the long term effects are known but disregarded because of it’s healing effects. Why then does marijuana have such a negative aspect on that? http://www.youtube.com/watch?v=TXKjRkkoIOU watch that and see how much it actually helps as a treatment.

  26. I’m a neuroscientist and as usual I’m horrified by many of these comments. MOST if not all the medical research in this country is funded by the government. To think that each individual scientist subscribes to some sort of conspiracy that needs to suppress the benefits of drugs of addiction is absurd. Scientists do science because they are interested in answering a question, and even better…most want to help humanity. This article merely highlights a study that suggests that marijuana has long-term effects that may be harmful to your offspring. If true…wouldn’t you want to know that?! Do you think the scientists that work on fetal alcohol syndrome, for example, are making their findings up to support a government conspiracy?! Think rationally people!

    1. You may be a professional by trade and you may call me guinea pig as far as the drug industry goes marajuana IS a gateway drug I’m 48 yrs old , I believe I qualify , started with weed , LSD , then freebasing . I don’t smoke weed anymore and it pretty much legal here , BUT the latter of those drugs I listed I’ve done for some 30yrs (gateway drug absolutely)

  27. Thank you for the article. notice the reactions. Any person that feels their beliefs and behaviors are being criticized will jump. Having said this, isnt it valid to hear boths sides to the story? Haven’t we lived with the results of outdated studies? Who is to say things we thought were good for us arent?

  28. “adolescent rats exposed to THC (the molecule primarily responsible for pot’s mind-altering effects) are more likely to self-administer heroin as adults”

    And this TOTALLY justifies pot alarmism, because drug use in humans is a COMPLETELY biological process with absolutely NO socio-cultural (and dare I say socioeconomic) correlations. In other words, thanks for supporting the systemic racism underlying current US drug laws by giving them the appearance of scientificity.

  29. As an author you should do your research and discover that small mammals lack the ability to rid THC from their brains, making any such experiments on rodents useless and irrelevant. It is irresponsible to write such an article based on this. Who injects THC anyway??? Shame on Nat Geo for printing this trash.

  30. Just a quick thanks Virginia. I really appreciate this kind of research to elucidate the real effects (including benefits AND harms) of marijuana use.

  31. Hi Virgínia. I really dont think they can make these assumptions from one litter or rats. All the “effects” can just be the parents caracteristics and predispositions. And marijuana is not a gateway drug, if it was, more than half of the usa would be doing hard drugs by now… a study just came out about how the increase in marijuana consumption was followed by a decrease in the consuption of hard drugs, so…

  32. The affect that marijuana has on the brains of users who conveniently use science that advocates the use of marijuana in their favor, but then resist science that does not, is significant. There should be a study done on this phenomenon alone.

  33. this piece is highly biased, you explained that the second generation rats were more sensitive to novelty in their environments (which could possibly be interpreted as possessing a higher intelligence) so the substance that was put into the cage was irrelevant, the rat would have investigated the button and if it contained a poison the study could have linked marijuana to suicide which is just as ridiculous as this conclusion. this isn’t science, it’s fear mongering. shame on you and Nat Geo for publicizing this propaganda.

  34. It is hilarious how personal pot smokers are taking this article. When people talk about cigarettes they say it “could” cause cancer they do not say 100% this will cause cancer. So stop saying this isn’t proper science. They will not use words of finality. I know it’s the “cool” thing to support marijuana but damn grow up. I hate hipsters

  35. Testy, aren’t they, Virginia. People seem to have very negative reactions to research that doesn’t fit their views, whether it’s about global warming, the earth going around the sun or vice versa, or the effects of pot on rat offspring (even when you acknowledge that such research results may or may not be replicated in humans). I think it’s just as silly to assume that we know all about the harm pot could do (or not) as it is to assume that we know all about how pot might be beneficial in some instances. I assume both. I suggest keeping an open mind about the possible good and bad. If your mind is closed, why even read?

  36. Do we ever do similar studies with alcohol, prescription meds, or even caffeine to the damage they do and what kind of gateway they proved to have? We all know how easy it is to get our hands on these and we all know how much more harmful they are to our body. This test is a joke and the story is thought up by editors desperate for website views. They know the hot topics and why wouldn’t they capitalize on it if possible. Especially if you can go against the grain now that the real (non harmful) side of marijuana is becoming more known and accepted in the public eye to raise some eyebrows and drive links to your site? Some marketing manager is smiling right now. Great work ma’am, great work.

  37. Absolutely pot is a gateway drug , I started smoking pot at a young age ! Moved on to something more powerful , freebasing cocain which in turn robbed me of unimaginable things . I believe in being honest , thats about as honest as I can get , if you would like to talk about this further feel free to Email mail me at derf652003@gmail.com love to tell my story …

  38. “This pointed to weed as a “gateway” into other kinds of addictive drugs.”

    Assuming weed is an addictive drug which has in no scientific journal ever been proven. In fact, it’s been shown to be less addictive than cigarettes, alcohol and even coffee. And does less damage than all of the above.

    So, why write such an uneducated article? You can’t say you’re pro legalization when you don’t even know the basics.

  39. Hi Virginia,
    Nice article, it was a good read, you are absolutely true that main stream media does not show details regarding the ill effects and not most of them are open to thoughts like this could happen. It opens your thinking, I do believe it is true but everything has an affect on the body, even working out does have its own side affects too. Even breathing oxygen kills us by accumulating oxidants in the body but that doesn’t stop us from breathing thou. Even the drugs that is available in drug store medically prescribed causes a lot of side effects but we still do use it because it cures. Marijuana or weed does the same effects on the body, it has a lot more advantages than dis advantages until proven otherwise. People have been using marijuana for ages now and that is a natural plant, I believe it us much better than drinking as well. Thanks for taking your time out for research, please can you share more information about the research in detail about the studies that has been made would be great.

  40. Are you kidding? I’ve never met anyone in life that has injected THC. Marijuana has many properties that don’t seem to have been used in this study.

  41. I don’t understand why everyone is attacking the author of the article. She presented evidence and potential implications. I assume that whoever is reading National Geographic is a fairly competent person. She isn’t being self-righteous and pushy. Read it with a clean slate without bias and it’s pretty compelling stuff. I found it really interesting.

  42. Virginia Hughes you and your jingoism packed article are more harmful to society that Marijuana is.

    You are just trying to bring light to some little know research?

    Why don’t you bring to light the research, more of which has been done in the past 5 years than ever before in history, that sheds light on exactly HOW HELPFUL cannabis can be to humans and their endocannabinoids system in each of us.

    You are more dangerous because this kind of misinformation appeared in Natural Geographic, and will serve to further propagandize marijuana (the ignorant call if pot. it is Cannabis) and will serve to assist in making families move to other states to help their CHILDREN.

    You are more Dangerous Virginia Hughes. You are.

    I dare you to meet a cancer patient that chooses to medicate with cannabis, and then walk away with the same armchair blog opinion with “Googled” agendized research as her source.

    You are more dangerous than your supposed gateway drug.

  43. I have a question about the methodology. I might have read wrong or passed it by without noticing but how can a conclusion, for the purposes of this study, as marijuana is a gateway to heroin when no control group was created, where that group of rats would not be expossed to marijuana and see if they sought out heroin more or less than thos expossed to it? Again, I might have passed it by, but I that would be a major methodology flaw.

  44. I just have to say–if these rats were exposed to the amount of THC in a joint every couple of days, what size of joint are we talking about? A rat is MUCH smaller than a human, if they are getting a human sized dose of THC every couple of days, yeah its gonna affect them adversely! Could you imagine how much pot an adult human would have to smoke to equal that amount of THC?? Now if we are talking limiting the rat to the amount of THC in a rat sized joint, I’d be more likely to take this study seriously. As the article is written, I’m assuming a joint is a joint–a regular, human sized joint. So based on this article, I find this study to be pointless.

  45. Sorry but this is a joke, I expected more from N.G then some b/s like this. Way to keep the fear and propaganda rolling….

  46. Well, we can use another source for long term effect of marihuana use.

    History. Marihuana has been used for at least, the last 10,000 years, and some the cultures that relied on its use made huge marks on history: Ancient India, Ancient China, Ancient Egypt and so forth, and these marks were made in a considerable diversity of fields: medicine, art, culture, technology, philosophy and perhaps even gastronomy. You don’t even have to go so far to see the long last effects of marihuana not just on an individual level, but in a sociocultural level. Carl Sagan was known to use marihuana in the aid of his cosmic theories. So if you guide yourself by the historic record, long term effects might be bad, yes, but so far bad consequences are biased and made larger in the public eye than the good effects it has had in global culture, which also matter. At any rate, weed use has been legal for most of human history, the reasons behind it being made illegal are mostly political and economical, which are always full of bullshit (pardon my french) so just by doing this assertion I can say there is actually no problem of marihuana being legal again.

    (sorry if I have bad english, it’s not my first language, I hope I made myself as clear as possible).

  47. humans have been using marijuana for tens of thousands of years if not longer.
    you want us to trust drugs that were just developed, that have only existed the span of a few years, not nearly long enough to have any idea what effects on our dna, or whatever you claim here that thc causes.
    what we know THC causes is apoptosis in leukemia cells. look it up. it actively cures cancer. wonder why we’ve had a modern cancer epidemic that correlates with marijuana prohibition.
    keep on with the scare tactics though. that’s cool.

  48. Great article, indeed it demonstrates that we should be more careful on what drugs could do to society. However, I would still would like more research to be conducted on this field.

  49. Well i am a complete pot head and i also believe whatever you saying might be true, but for some reason am not going to give up pots because with what you have explained which you did very well by the way and please ignore all these ignorants who just sit on internet after having fights with their husbands/wives and they need to lash out at someone and so they do it on internet on who ever they face first. Keep up the good work. fi Amaan Allah.

  50. Those who argue that this study “proves” that marijuana should continue to be outlawed are missing the point. I am not a marijuana user, not because it is illegal, but because I believe that smoking marijuana has side effects that I do not find desirable. However, so does drinking alcohol and eating potato chips. The debate on legalization should be about whether or not the government should outlaw personal behavior, at least in so far as that behavior is not harmful to others. While it should be illegal to operate a motor vehicle under the influence of drugs and alcohol (because of the harm one could cause another), it should not be illegal to toke up in the privacy of your own home. Smoking in public should be illegal because others should not have to breathe your second-hand smoke, but if you are by yourself or with other consenting adults, the government shouldn’t be able to tell you what you can or cannot put in your body. Minors should also be outlawed from using as they are not mature enough to make those kinds of informed decisions for themselves. We waste millions of dollars each year fighting a drug war that we have no chance of winning. Either you want to use drugs and alcohol or you do not, and those who do not will not suddenly start using because it is legal. And we should absolutely continue to study both the harmful and beneficial effects of marijuana use so that adults can make informed decisions about their own bodies and habits. Frankly, it isn’t anybody else’s business but their own.

  51. Has this study been tested on tobacco. Tobacco I believe is more of a gateway than any other drug. Yet very little research is done on the effect of nicotine in these same areas of the brain. Maybe it’s hidden knowledge by big tobacco not sure.

  52. This is scientific data, extrapolated to interpret this study in lay terms. The fault I read is in the extrapolation and not the study. The adolescent brain is still developing and is far more vulnerable to a wide range of epigenetic influences than an adult brain. There is no claim in this article that THC is worse than alcohol. Alcohol has a similar range of well established issues, many quite similar. The primary issue in the data is the administering of any of these compounds, THC included, to non-adult brains. The brain’s job is to adapt and integrate, and this is what happens with nicotine, alcohol or grass when consumed under 25 years of age.

  53. Ugh. Seriously? If nothing else, this comments section clearly shows that cannabis use impairs verbal reasoning and logic.
    Do most of you know nothing about science? Yeah, scientifically it would be great if we could keep humans isolated for their entire lives and give them cannabis, force them to mate with one another, steal their children away to be raised in the same environment with non-potheads. Is that ethical? Do you think that is a viable alternative to rodents? No. No. And no. Science does its best within the realm of our ethics and the availability of funding. What’s usually the best under these circumstances? Rats and mice.
    Do you know what other types of research uses such model animals? Yeah, pretty much everything in biomedical science. That pharmaceutical you took this morning? It’s almost certainly rodent-approved. This is what researchers do. You test things in lower mammals before higher ones (if you’re able to do this at all). You test components of drugs to piece apart effects. The researchers’ next step is likely to test the other components of cannabis.
    Not everything has an agenda. Do you have to take funding into account? Sure. Could it maybe produce a biased interpretation? Sure. These are quite stark results, though, and it’s hard to get the opposite interpretation from the data. However, you’re the pot calling the kettle black if you can’t look at this objectively yourselves. If anything, you should welcome additional information. More of it allows you to make the best choice possible.
    Also, to the ‘“possibly linked with” or “could result in”’ commentator, you don’t seem to understand the difference between correlation and causation. Correlative studies are usually the first step in investigations. They can’t prove anything, which is why researchers RESPONSIBLY are careful in stating what can and cannot be gleaned from their data. They then wish to show the significance of their work and suggest further studies. This is why you get the “could” and “possibly” and “linked” usage. They’re showing you that they don’t have the data to prove it, just to indicate it. Experimental studies work to actually prove something. The main piece of research discussed here actually addresses this. That’s why you can say that, in rats, THC is a gateway drug. “Is” not “might be.” However, this research does indicate that, in genetically similar humans (about 97.5% of working DNA compared with mice), there may be the same effect. Did this study show that there “is”? Nope. Does it lend evidence to the hypothesis that it does? Definitely That’s why it’s stated that way. There’s no conspiracy.

  54. I think, when scientists have evidence, & I mean real substantial evidence where it shows real harm to the next generations, studies made with real humans, not RATS, then you can argue all you want, I have read a lot about it & I don’t see any harm WHAT SO EVER……….Thank you

  55. Did anybody else read the sentence “Several years ago, Hurd and her colleagues showed that adolescent rats exposed to THC (the molecule primarily responsible for pot’s mind-altering effects) are more likely to self-administer heroin as adults than are rats not exposed to THC.” and just couldn’t take the rest of the article seriously. I started to picture tiny rats with tiny needles shooting up heroin in a back alley.

  56. How much did Rupert Murdoch pay you to write this propaganda? You want to know about long term side effects? You forget things that arent that important in the first place. Big deal…your kids arent going to be heroin addicts just because you smoke grass. Med cabinet full of legally prescibed medicines? You might wanna worry, because your kids will steal them, they will take them, and they will have a higher likelyhood of being addicted , but thats what the doctors want, they want you addicted because you put money in their pockets. Virginia, you are spreading lies with shoddy research.

  57. Alcohol and junk food cause changes on your DNA that can be passed to your offspring too yet those things are legal and now we have a world full off alcoholics and obese people with diabetes. Why don’t we just make those things illegal too? You can inform people of the consequences but they’re still going to do what they want.

  58. We’ll right off the bat, this entire experiment is badly flawed. It has been well documented in countless studies that injecting artificial THC, or even naturally derived THC has Nothing to do with smoking a joint as far as what happens to your body and or brain. What a poorly studied and carried out test. Epic Fail!!

  59. You CANNOT be hit-or-miss when it comes to this issue. Let me present myself for consideration. My parents both smoked cigarettes, and also drank in excess frequently. My parents have also both partook of marijuana, at least. I tried it myself, as a teenager, several times. I have declined or flat out refused other drugs, and I currently do not smoke, yet I support it because even comparing it to things such as heroin or even Vicodin is mind-blowingly ridiculous. Have you truly been testing without prejudice? Look at me! I am successful, I haven’t come near it or any other drug in over a decade, I am beautiful, very intelligent, caring, strong, and wise. Back to the drawing board, boys, and leave your preconceived notions at the door!

  60. Please do some actual research, go and compare some studies done outside the US. There has been one going for over thirty years in Canada, studying people and the effects. European countries also have scientists who are not mandated by the DEA.

    You call yourself what a blogger? Definitely not a journalist.

  61. Ok come on people lets grow up now. I am all for the legalization of pot I know it can’t have as harmful effects as alcohol!!! that being said I don’t think it is right to say this is a bad article or poor journalism. She is just saying the test results COULD cause problems for future generations. I believe that further testing is needed and I don’t think the test was right but if there is a possibility of future problems people should be informed however I do not think that this study should be a factor in deciding if pot should be legal. I say if alcohol is legal then pot should be because I know for a fact that the damage that alcohol causes is far worse than what pot could ever do!!!

  62. A “joint’s worth” for a rat is a lot more than it is for a human. That is unless they mean they administered smaller doses daily which add up to about a joint’s worth every few days.

    I smoke high grade cannabis every day, go to the gym four days a week, run a 7 minute mile, and am one semester away from my bachelor’s in Information Technology with like a 3.9 GPA. Study this.

    I also know that activating cannabinoid receptors triggers an influx of positive ions, raising the threshold for affected neurons to reach action potential. This is because endocannabinoids (ie. anandamine, a molecule with 5 times the affinity for CB receptors as THC and produced within the organism biologically) are released into the synapses by neurons after depolarization and accumulate in extracellular fluid, the more times the neuron fires the greater the concentration and the more CB receptors are activated. This is supposedly a “new frontier” of study, but the problem with science today is that it gets hung up on the scientific process when sometimes all that is needed is some common sense.

    Neurons release anandamide after being activated, the more intensely the greater the concentration. The effect is CB receptor activation (retrograde), with the result that neurons become less apt to fire again due to an influx of positive ions, moving the polarity away from the action potential. Reason should have it (skipping years and millions of dollars in scientific research here) that this is because overusing a neural pathway too much in a short period of time is harmful. Adding to this is the science showing that CB receptor activation triggers an increase in myelin synthesis by the glial cells surrounding the neuron releasing the cannabinoids. This growth of the myelin sheath significantly increases the ease with which the neural pathway can transmit an impulse in subsequent activations. Clearly, and soon science will show (this is something I researched to great extent about 5 years ago: https://www.facebook.com/notes/alex-nordeen/theory-on-preventing-neural-degeneration/47183996972) the purpose of the endocannabinoid system is to directly strengthen the neural pathways we as humans use, or any animal for that matter, the chemical mechanism for increasing signal transduction built in to the very process of neural activation, anandamide release triggered by depolarization of the cell. Therefore, all weed does is mimic this process, dampening the central nervous system with more of a blanket effect than site specific anandamide release, but also likely contributing to greater levels of myelin production throughout the organism as well. I think of it a a neurological supplement, but then again I’m much more health conscious than the average cannabis consumer.

    Clearly I’m not an English major, but if America could bear with everything I just put into text there would be no question as to whether or not Americans should have access to plant derive cannabinoids, and that they are in fact more likely to marginally benefit to the organism than to cause it harm. What we really need are cheaper vaporizers. Hot smoke is always a bad thing, probably counteracted by cannabinoids’ strong anticarcinogenic effects but I won’t even get into that..

  63. Virginia, I find the whole field of epigenetics fascinating and feel it explores areas of science that can be intuitive. Thanks for opening up this area of science to your readers.
    A science teacher

  64. First of all, if you are writing for Nat Geo, fix your typos. Secondly, this article is extremely biased, and I’m very disappointed in National Geographic for allowing such a thing to be published. I agree with the comment above, if it were a gateway drug, a much higher number of people would be doing hard drugs by now. Get your facts straight. This is absurd.

  65. Rats are not humans, I wish researchers would stop throwing rat test results at the public. Are you a rat? No, you are not therefore your reactions to substances would be somewhat different, I should think.

  66. So, this blog or whatever this is, really makes me laugh at the selfish views of classic ney-sayers. How can you say Marijuana effects humans when clearly all youve tested on is rats. Id like to see you test humans first before making assumptions like this. Also, if you think “weed” is so harmful, I bet you money that millions of people who blaze regularly are smarter, more athletic, and generally a better person than yourselves. Why does this even bother you? Weeds been around for decades and everything is evolving. I dont know it seems weird to me.

  67. I speak first hand at what dope does to you and your family. I come from a family that has addiction in its genes, my grandfater was an cronic drinker as was my father. You see how addiction passes through generations. I drank a lot also but quit 20yrs ago, but, when I was introduced to dope it had me hooked immediately, I was 16 and I quit 3 months ago, Im now 54. Also I have a daughter whom had Endometriosis when the medical proffession did nothing because she was 15 by the time she was 16 she was not coping and I gave her a joint, she had the best sleep in 2 years but unfortunately I did the wrong thing as she is still addicted and wanting to quit now also. We will get there. Society has to realise that our brains are hardwired for wanting more, it just depends what that “more” is. My sister was a Gambling addict. Smoking affected my life and body, since I quit, in three months I have put on 8kilos in usa thats about a stone, I have liver disease and on my fibrosis test only 2 months after quitting it went from 28.7 to 13 so I am nearly in the normal range. My skin and overall looks have changed so much people say I look about 40yrs old now. Also I did have a period from 43 to 48 that I was introduced to Iv speed, that was the darkest time of my life and I quit without help, actually I quit everything without any help from the Government or it organisations. I am over hearing about the science and wish that scientists would correlate the addiction problem with family concerned and apply their results to actual families. The Government needs to see that societies and family structure and addiction all have a debilitating affect. Isnt this called the domino effect. Addicted people can also only give up if they want to. So that issue needs to be addressed. How do you make an addicted person want better when their mind is in such turmoil. Hope my input helps.

  68. It would be a legitimate criticism of the Facebook summary of Virginia’s article to say that the summary led the reader to believe that the article was referring to research on humans.

  69. Jason (Neuroscientist): Thank you for your feedback. As i read through these comments, its fairly clear to see that weed smokers most likely are addicted to [it]. I am merely basing this idea on how deffensive they become over this topic. Interestingly shines light on points this column tries to make.

  70. This study was published in 2012 and was the only one of its kind to link alterations in the opioid protein activity to higher vulnerability to heroin. Moreover, the study only concludes that the THC decreased the regulation of the gene that controls the production of opioid polypeptides in adolescent offspring.
    You could suggest that THC in its pure form might make your offspring more open to opiates in general during their adolescence.
    There is evidence enough to write this article, but I would like to see the findings built upon or reproduced. The lack of background information included in the article is close to nothing, and I would expect more of an institution like NG.

  71. How exactly does a rat self administer heroin? I know there are risks, but I wonder if they did the same study with alcohol and prescription pain meds if the finding would be worse. Both of which are legal.

  72. It only makes sense that past experiences would effect future generations. Especially in a fast reproducing species such as the rat. For testing purposes it makes sense. I’m sure its much quicker and safer (less contracts and lawyers). However, when you say that the rats “were more sensitive to novelty in their environment”, does that mean they were more curious by objects in their environment? Or, that they would consume substances the control rats would not?
    I was also curious about the significance of using Heroin. It is highly addictive correct? If the rats were exposed once, wouldn’t they seek it repeatedly after being introduced? And as far as the likelihood of a second generation human being becoming a heroin addict, there would be many more variables. We are not all presented with Heroin on a regular basis. Parenting, personal choice, neighborhood, childhood would all factor into ones decision making process. At least I would hope. So I don’t necessarily agree with that theory. But I get the gist.
    I’m not saying that it is unbelievable that THC may be some kind of gateway into trying other mind altering chemicals. But aren’t there a great deal of other substances that could also be contributing to this increasing “gateway” fear? Nicotine for example, is one of the most highly addictive drugs consumed on a regular basis. That and alcohol both of which seem just as, if not, more dangerous than THC which has been around for just as long. It would be awesome to see a comparison study including effects from other controlled substances! Perhaps it is genetic learned behavior to enjoy yourself.
    I enjoyed your paper, very interesting. Keep questioning everything.

  73. Important question left unanswered by the article: Did the first generation of rats participate in the heroin part of the experiment before they produced their offspring? If so then that would be a serious flaw for obvious reasons, but the article never mentions whether heroin use might have been the cause of the transgenerational weakness for heroin. I’d also like to know the exact daily dosage of THC intravenously administered to the rats, as someone who works with pharmaceutical databases and the FDA I’m pretty familiar with the importance of that (mg per kg body mass).

  74. If main stream media hasn’t talked about this yet then please explain the failed D.A.R.E. program! I don’t think we need anymore studies!!!

  75. Virginia–you should know better! Americans are IN LOVE with pot. It’s like trying to tell a guy that his new girlfriend he is in love with is cheating on him. You just don’t cross those boundaries! Haha–the funny thing is is that every soul here has to eventually detach themselves from their addictions to the earth. They just don’t remember that is the deal! Love it! So please, don’t give them negative points of view–tell them what they want to hear! DANG–if only Americans were as passionate about human rights, doing volunteer work, gaining knowledge and wisdom, seeking God as they do for the sanctity of a plant–this world would be awesome! <l:D Forgetful souls amuse me!

  76. Bueno al respecto el consumo de marihuana no produce daños irrebersibles en las personas que la consumen como el daño de otras suntancias adictivas, pero este informe habla en la segunda o tercera generaciones de las personas que la consumen.Por esa razon las personas que consumimos marihuana tenemos que tener encuenta todo lo que genera al nivel molecular o ADN que podria ser infringuidos en nuestros hijos.Por lo siguiente unas de las leyes de Darwin tenemos que asegurar la sobrevivencia de nuestra escepie,en otras palabras tenemos que ser responsable con el uso de la marihuana por que no es nociva directamente en las personas que la consumimos el problema es nuestros hijos

  77. You know whose intelligence I’d trust less than a cannabis user’s? Anyone who still believes in the gateway theory in 2014.

  78. Dear Author,

    Thank you!

    Do yourself a favor and don’t respond to individual comments. You’ll drive yourself insane. People, as a general rule, are morons. Internet trolls are atrocious!

  79. Its funny how many people smoke pot but have never tried hard drugs. I guess you can say beer drinking leads to drinking liquor, using the articles example. I know several people who have smoked and have never tried anything else. Unfortunately many people would rather believe the fear instead of looking for non government funded propaganda. More studies say it is not near as harmful than society leaves people to believe. To many people would rather believe what they are told instead of educating themselves and gaining insight on truths!

  80. well i have been smoking weed since 21 years and still smoking 1-2g a day (i love my weed)
    However !
    it definitly was the gateway to me using other drugs (1-2 nearly killed me)
    in my eyes making weed legal is a really BAD idea.. look at it this way i started smoking weed at 12 years old and by the time i was 18 i was hooked on crack, boshed over 500 lsd tabs (not at the same time) boshed over 1000 ecstacy pills (again not in one go) and the list goes on, the point is do you really want your teen kids ordering bags of grass on the internet (it could be that easy with pay and go creditcards) only to find them selfs doing harder drugs. i can safely say over 50% of people who smoke weed regularly for over a year will try a line of cocaine..(not good)

  81. So many haters here who feel pointed at by this article. It by itself says “however this is a study only made in rats” and also tells at first the well known good aplications of marijuana. Read well the article, it is not trying to scare anyone away and is also not saying “if you smoke weed your children will be addict to heroine!” it only tells what have been finded in the lab, and that is, the mice that have been exposed to marijuana and it’s offspring seemed to be more likely to push a button that injects them heroine. This seems like a really politically correct post but you only read hate when you see it talks about possible bad effects of marijuana.

  82. Why do you refuse to present the other side of the argument? The countless studies demonstrating the medical benefits of marijuana? The burgeoning field of research into THC as a cancer-fighting substance, with its ability to inhibit the growth of tumors? The millions who consume state-regulated, legal, and taxed plant flowers that grow naturally out of the Earth?

    Why aren’t we analyzing and critiquing the perverted perspective that you have, with citations of studies that not only stand in the face of science–the hypothesis of inheritance of acquired characteristics was disproved long ago–but also utilize flawed methodologies, such as administering the same amount of THC to rats as a human would supposedly administer to oneself?

    This article is radically wrong and the author is not a journalist. Don’t be fooled–inform yourself on the issue by visiting Wikipedia: http://en.wikipedia.org/wiki/Cannabis_(drug).

  83. I understand that this article is based off the Swedish study of generational inheritance, but it makes a serious flaw in in accurately representing how these changes were recorded. By placing the rat pups with a mother that wasn’t their own they may have not been licked enough, which would not stimulate the proteins which would activate a serotonin response and lead to other nature/nurture issues. These results could be the result of weed or the result of not being nurtured appropriately.

  84. Virginia, thank you.
    I am sincerely sorry for the abuse you are getting in the comments. No doubt you are used to this as a journalist, and perhaps you do not have time to even read them all. But, I enjoyed your article. Certainly, marijuana is a medical drug for certain illnesses. And all drugs have side effects. Thank you for writing about the research being done to learn more about the side effects for this drug.

    Interesting to see certain trends in the comments, such as “rats are not humans” (no, but most drug research starts with rats), “could doesn’t mean it will” (science inherently never provides absolute answers), “it’s government funded propaganda” (well, the government funds most medical research), “why haven’t they testing other drugs this way?” (someone probably has, but, even if not, this study is not claiming to be a comparative analysis between drugs).

    As another comment thankfully pointed out, let’s be rational here!

  85. This is ridiculous. do these people actually have credibility? the study says rats whos parents were exposed to thc are more likely to “self administer” heroin via a lever they press than those who’s parents weren’t… now instead of saying “rats” lets say people and instead of saying “labs” or “levers” we say Government institution. had the government never refined and introduced the heroin in the first place this test is invalid. heroin unlike marijuana does not naturally occur in this world. but hey painkillers is a #1 seller for the pharmaceutical industry which is regulated solely by the what? –> FDA.. (cough) aka Government. wake the fuck up. weed doesn’t make me want to do dope unlike other thinks like alcohol that do trigger an addictive personality inside me. but ohh yeah that’s also regulated by???? u got it. wake the fuck up

  86. This is ridiculous. do these people actually have credibility? the study says rats whos parents were exposed to thc are more likely to “self administer” heroin via a lever they press than those who’s parents weren’t… now instead of saying “rats” lets say people and instead of saying “labs” or “levers” we say Government institution. had the government never refined and introduced the heroin in the first place this test is invalid. heroin unlike marijuana does not naturally occur in this world. but hey painkillers is a #1 seller for the pharmaceutical industry which is regulated solely by the what? –> FDA.. (cough) aka Government. Weed doesn’t make me want to do dope unlike other thinks like alcohol that do trigger an addictive personality inside me. but ohh yeah that’s also regulated by???? u got it. wake up!

  87. I appreciate your article. I smoked weed a fair amount years ago and certainly hope I did not pass anything bad to children. But personal evidence seems to indicate they are both doing well and having healthy babies of their own now. What is most troubling is the fact that so little research has been done on the effects of THC and the over 400 other chemicals found in marijuana. This is totally due to the fact the marijuana is classified as a Schedule I narcotic (same as heroin) so even using it in a study broke Federal law. Forget about getting any federal funding. So we are a little late in figuring out what it does to us. Don’t get me wrong we have to do the studies. I believe they are vital but let’s face it,this genie got out of the bottle a long time ago.
    Well written article though. Thank you.

  88. It is very sad to see the very respectable NG take part of the propaganda against weed as has been practiced since Nixon to please the lobbies of alcohol and cigarettes. The things that the experiences want to establish as fact have such a vicious edge that it is incredible that serious scientists would think of them. That demonisation of this plant is becoming a very perplexing issue when alcohol and tobacco are legal.

  89. National Geo, I’m hurt. In the study it says they gave the rats a joint worth of THC injected once a week. Very unscientific, I’ve never met a human that injects THC, also marijuana doesn’t just have THC in it, and without all the other chemicals in pot, the study is pointless, they could balance out the reported cross generational effects of THC. And then there is the issue of scale, rats last time I checked are on average 1/100th the size of humans, so injecting them with a dose of THC equivalent to the amount in a joint means they were getting proportionately 200 plus times the amount of THC the average pot user gets, as joints are usually are shared lol. As THC is an exo-cannabinoid and replaces natural endo-cannabinoids in your brain,( that’s how pot works by the way), it should be no surprise that rats getting the proportionate equivalent of a human smoking 200 joints in the time it takes to get an injection, once a week for an extended period of time, has the potential to introduce adversity.

  90. Listen guys marijuana can help people with some specific diseases, but for normal people its very addictive and they tend to cling on it and use it for their own reason which is self gratification or making them happy. Imagine guys kids from 12 to teens 16-18 using those kinds of drugs. You can see them walking in the streets or eating in your house with red eyes and smiling faces. Imagine if that is your brother or sister or son/daughter. People who said marijuana is healty is too selfish and self centered come on if your healthy then why use it? Because your lonely or sad? They are other things to do to make you happy. Don’t depend on drugs it will really affect the next generations. Now younger age have already been exposed to these kinds of drugs and smoking pot is like the stepping stone. Some of the dealers of marijuana introduce the buyers to other stuff and that’s a fact don’t deny it. Anyways, I salute those teens who can control or can get away with these drugs easily.

  91. I don’t have as much of an issue with the evidence presented in this study as I do with the way that the results are framed. Even the image on the top of the page implies that these results are immediately applicable to human beings. Additionally, this study focused on only one of the chemical components in marijuana, while there are many others to take into account as well. This article should have included “THC” in the title, rather than “weed.” This leads individuals reading the article to read further into the results than even the scientists doing the study did. I would be more likely to trust a source which aims to teach the findings exactly as they were discovered because it is inadequate framing like this that creates misconceptions about marijuana on BOTH sides of the argument. I very much respect that there are studies being done on this topic, especially at a time where it may become legalized and individuals need to be informed about the real effects marijuana has on the body: good and bad. However, articles framed in this way only create more conflict and hinder the understanding of the general public.

  92. These may ALL be viable research, but whew is ALL of this data when considering tobacco is legal, or alcohol, hell alcohol is said to be hereditary as well through generations and can lead next gen. Of those who consumed to be alcoholics, but not all are, I find myself to be a perfect example that while I occasionally do enjoy a guinness, not really even socially, I do NOT require the stuff…….. so why would marijuana mean ANYTHING different for me?

  93. I bet if you posted an article saying something like “marijuana use grants eternal life and god-like powers” everyone would be praising the author and Nat-Geo. No one likes the truth if it goes against their beliefs, that’s just the human condition I guess. It’s an interesting read no matter what side of the spectrum you sit on.

  94. So now we are like RATS! Come on all this is about is the FED’s trying to stop the steamroller of legalizing pot from continuing across the nation.

    They have been testing pot for 80 years and NEVER once came up with anything even close to this. And now all of a sudden there is this HUGE revelation! isn’t this convenient!

    On top of that do you honestly think that Humans in any way would react the same way a RAT does? Plus the levels of THC that are ingested during smoking are not anywhere close to the amounts that they are injecting into those poor rats every day!

    It’s all a bunch of bull and I am extremely upset with National Geographic for posting this, to the point of no longer continuing my magazine subscription.

  95. Most scientific research actually does not support the claims made in this article, so saying that people get testy when they are confronted with the actual research is a farce. Rational and intelligent people get suspicious and irritated when they see highly biased claims in direct opposition to the scientific consensus. This is akin to a climate scientist denying the effect man-made combustion is having on global warming.

  96. Virgina, Thank you for your efforts. You are obviously seeking to present a perspective with regard to cannabis that you feel is important.

    That being said, if this study really has impacted your thoughts about cannabis being safe, you need to do more research and think this things through a bit. There are so many reasons why this study has absolutely no bearing on the reality of cannabis use among humans being quite safe. One of the keys to writing well about something is developing a deep understanding of the subject.

    The roots of cannabis being illegal in the US are entirely about William Randolph Hearst wanting to A). Limit competing interests access to cheap labor, namely, Mexicans and B). He did not want Hemp competing with his paper mills which were built around processing wood pulp, also, he was a bit of a timber tycoon. If I remember correctly, the DuPonts were involved in this also. They created the chemical treatment used in making the wood pulp paper.

    As a journalist, you have a responsibility to always present the truth to ensure you are informing your readers so they can vote intelligently.

    This is a piece which needs to be given more time and more thought.


  97. We have heard all of this propaganda before, the exact same thing, for the last 50 years. This is no more than bad journalism just intended to scare people. Every study now, since legalization research has skyrocketed, shows benefits of the “drug”, shrinking tumors, increasing cognitive brain function, reducing insomnia, natural pain killer, non addictive, etc etc etc. Yet you feel the need to post flawed research that is identical to the scare tactics used for the past 50 years all from researched linked to pharmaceutical companies and somehow call that journalism? And even worse put it in National Geographic?

  98. You feel we don’t agree with this research because we don’t like the result, that’s not it at all. This research is injecting THC into rats and the result is supposed to be conclusive across the board? No, if you know research mice are what you essentially just start out with, the likelihood of the benefits or the consequences being the same in a non controlled environment with a human is very rare which is why we have clinical trials. In this case the THC is injected instead of inhaled like it regularly would be. When you smoke you lose THC in the process. Also how much THC did the bud contain. There are many factors and you can’t be mad for others seeing those and disagreeing with this based on facts.

  99. You can’t just have THC, you got to have CBD too, to balance it out. CBD in cannabis is the counterpart of THC… Of course pure THC isn’t good.. And did they get injected with an amount that is proper for its size? Rats have different brains than humans. Isolation in many forms makes it easier to want to do drugs.. This goes for humans and rats. Were the rats that started with heroin isolated one by one in tiny, unnatural cages, with no activities for the rat? Rats are highly intelligent and social animals. If you did the same experiment on rats that had a lot of space, activities and other rats with them, the results would most likely be different!! Google “rat park drug experiment”

  100. To those wondering why “potheads” make a big deal about these type of “studies”, It gives credence to those that want to put me in jail, remove my ability to vote (felony) and deny me federal school grants among other things.

  101. I read the article and I read the comments….interesting how people get angry when someone points out a bad habit…well in my case I been around potheads all my life my father did and my brother still is and my sister fighting the addiction….and its bs when people say it has no side effects….I look at my brother and his life and what the drug did to him and its not just a gateway drug it produces big brain damage…and so many of my childhood friends are proof for that….legalizing it wont make it better nor will it stop crime…smh

  102. As an ex-researcher and a marijuana user, I’m sincerly interested in the results of this study. However, the abstract does not show any data that helps my to interpret their results and since I do not work at university anymore, I do not have access to the damn study. How the hell are you suppose to educate people without showing data?! The abstract does not even mention the factor of significance of their data!

    Even better, Jeff in the comments section refers to this study, from the same author; which shows the exact opposite behavior through the compound of CBD, also found in pot: http://m.jneurosci.org/content/29/47/14764.full

    The moot point is, this study only researches THC, which is just one of the many compounds (allthough it represents the largest quantity) that cannabis possesses. Yasmin Hurd and all the so called ‘scientific journalists’ however, do not seem to distinct between THC and cannabis nor assure that the two are not necessarily the same. If anything, this study says that you better can smoke the plant for sakes of medication rather than taking pure THC.

    I really am trying to take this study seriously but without the proper data, this research is making it hard to get a point across.

  103. I am dismayed by the calls to take this article down. What happened to freedom of speech. Give people the evidence and let them decide for themselves. I am smart enough to work out if an article or piece of research is flawed but I value the opportunity to make that judgement for myself without being bullied by people on either side of an argument.

  104. another crucial point is the goal of the study:
    ” The researchers stress that while a lot remains unknown about the mechanics of cannabis abuse, the body of existing research has clear implications for society. “It is now clear from the scientific data that cannabis is not harmless to the adolescent brain, specifically those who are most vulnerable from a genetic or psychological standpoint. Identifying these vulnerable adolescents, including through genetic or psychological screening, may be critical for prevention and early intervention of addiction and psychiatric disorders related to cannabis use. The objective is not to fuel the debate about whether cannabis is good or bad, but instead to identify those individuals who might most suffer from its deleterious effects and provide adequate measures to prevent this risk” Jutras-Aswad said. “Continuing research should be performed to inform public policy in this area. Without such systematic, evidenced-based research to understand the long-term effects of cannabis on the developing brain, not only the legal status of cannabis will be determined on uncertain ground, but we will not be able to innovate effective treatments such as the medicinal use of cannabis plant components that might be beneficial for treating specific disorders,” Dr Hurd said.”

    So I hope miss Hughes is willing to stand corrected and admit that her article is only seeking thrills and web hits.


  105. I really enjoyed your comment Francis Noyes. I was just about the write a comment along the same lines. This research project reminds me a lot about the one they did in 70s. The research placed gas masks over a number of monkeys and forced anywhere from around 30-60 joints a day. The results came back with negative reviews…Well duh. When I see these reports like these I just laugh because I always seem the find more useful information in the comments .This also mad me a bit sad Nat Geo. Your better then this.

  106. First off, I have a huge problem with the title of this article. Marijuana is NOT a gateway drug. If anything is a gateway substance it’s breast milk. The gateway theory has been debunked for some time now. Millions of people smoke pot each month. If the gateway theory were true, then shouldn’t we have equal numbers of pot smokers as heroin users? Secondly, as other posters have pointed out, who injects THC and who ingests that amount in that short period of time? And who smokes just THC? Dr. Gupta’s Weed 2… mentioned the Entourage Effect which is being negated by this study so it can’t be a realistic indicator of long term effects of cannabis usage. Thirdly, why just heroine (which is highly addictive) and not other addictive substances like nicotine or even caffeine? Lastly, yes, this study being funded by NIDA makes it highly suspect from the beginning in that 94% of all the studies done in the U.S. only look for the negative effects of cannabis which demonstrates a huge bias. I am for ending the drug war and certainly for legalizing pot. I found this article interesting to a point but I have to say this research seems very flawed and thought NG would have higher standards than this.

    BTW- My mother was a heroin addict at one point in her life and a heavy pot smoker and alcoholic all of her life (as well as dabbling in other illegal substances). I have NEVER had the urge to use heroin. Sure I have smoked some weed in my time (and of course drank alcohol) but have never gone on to use heavy drugs like heroin or meth or crack, etc. I will admit I’m addicted to nicotine, though. But, I will also admit I quit smoking cigarettes for two years with the help of some good ole herb. It was environmental factors that made me pick up that nasty habit all over again. i.e. socially.

    Please NG, if you are going to publish articles like this, then you ALSO have to publish articles that study the medicinal benefits of cannabis as well. Or does NIDA have you by the gonads?

  107. First off giving a rat a joint worth of THC at a time would be like a human smoking a pound of marijuana at once. Over-ingestion of ANYTHING is bound to cause an adverse reaction. Secondly, is it not likely that removing the baby rats from their biological parents and handing them over to a foster parent could cause behavioral consequences? In my opinion the studies themselves seem heavily botched if not purposely biased.

  108. The documentary “Super High Me” seems to have more scientific integrity then these so-called studies. Maybe the researchers were getting high on their on supply. What a joke.

  109. As someone who is studying medicine, I can truly say that this is the biggest load of bullshit article I have ever read. Are u working for a pharmaceutical company or something? This is irresponsible and I have just wasted a few minutes of my life even reading this.

  110. I think this article is very thought provoking, obviously by the other 120some comments im not the only one. I dont believe Virginia is trying to make any claims but only encouraging the public to look at both sides objectively. Obviously rats arent humans but thousands upon thousands of other studies are done on rats and we all gladly accept the outcome of those studies, so why is this one different? Lets just say some of these studies are one sided, I think i could also say that everyone posting on this comment board is pretty one sided (including myself.) I grew up in Mexico so ive seen the effects of the drug war first hand, i also mentor kids here in the US and ive seen the effects of pot on teens first hand. Both of these things are big issues that need to be addressed. I dont think there is an easy answer, and i dont think discarding scientific evidence is wise. Just my two cents.

  111. Greeting from Canada.
    Nat Geo please dissassociate yourself from Virginia Hughes and all fraudulent unbiase research organizations. Virginia does not seem to know how proffesional research is cunducted.
    Firstly the mices should not have been separated from their parents, this may aggravated or created an mental illness whitin the young mices.
    The title of the article is also fraudulent. This research is in no way conclusive of this. The writer of this article must hardly know that any substance will be memorised by our dna. Anyone here that aggrees that Virginia Hughes should seek employement outside of Nat Geo..should contact Nat Geo I will be doing the same. Sorry for spelling and grammair. English is not my first language.

  112. Thank you for using my photo for your article!
    It has been featured on a few other marijuana related articles,
    as well as on Gawker on an article about if today’s weed strains are way more potent than those of the 60s.


  113. Kids shouldn’t smoke weed, their bodies and minds are still developing. This is the same reason they shouldn’t drink alcohol, or do some other things that it’s fine for adults to do. You are taking one study about how weed can affect kids and applying it to adults, that’s your first mistake. Your second is putting so much emphasis into a study on rodents. I work with clinical trials. You pass yourself off as trying to portray the real science, yet you don’t know that it is extremely common for drugs to have results (either good or bad) in rodents, but then ultimately don’t have the same effect on human beings. Using one limited study on the effects of young rodents and acting like this disproves the enormous wealth of research on weed done by Harvard Medical and other major medical associations which conclude that weed is a mild drug that does little harm, though it should be avoided by children/teens and the mentally ill.

    I am extremely disappointed in National Geographic for printing this article and representing it as scientifically sound.

  114. I’m surprised and disappointed by the objections to this article. For 40 years government and other authorities have blocked research into marijuana that would have led to a fact-based understanding of its effects, and possible changes in public policy as a result. Decriminalization advocates have vigorously objected to this obstruction, rightly calling it unethical and unprincipled. Now that the tide turns toward decriminalization, an article that discusses research critical of marijuana draws howls of indignation and implicit pressure to suppress the information. Readers have to decide if they are interested in the truth, or just validation of their pre-existing position. I applaud the author for seeking and printing the facts wherever they may lead. Keep it up!

  115. Also, it is sadly clear that Virginia Hughes does not have a background in clinical research and does not know how to correctly interpret clinical findings, by the way she jumps from “young rats in a poorly controlled study given enormous amounts of a concentrated drug that is far stronger than any human would ever use” = compelling evidence of the dangers of a moderate amount of weed on adult humans. I expect non scientific publications to neglect to use actual research scientists to review research material so that they can correctly relay the information provided, but I would have expected better from Nat Geo.

  116. “Readers have to decide if they are interested in the truth, or just validation of their pre-existing position. I applaud the author for seeking and printing the facts wherever they may lead”

    Scott, the issue isn’t reporting research (all well and good). The issue is her misrepresentation of that research in order to scare readers. Plenty of people here have pointed out in the comments specific glaring problems with both the original research study and its application to humans. You trying to paint well articulated scientific criticisms as a bunch of ignorant stoners who just don’t want to hear the truth because it is inconvenient is blatantly dishonest, much like this article!

  117. Now that the tide turns toward decriminalization, an article that discusses research critical of marijuana draws howls of indignation and implicit pressure to suppress the information.

    As I said before, the well has been poisoned by a century of superstition, sadism, racism, and political opportunism (which is still going on). Just as we cannot have a reasonable scientific discussion comparing the abilities of races and ethnic groups, or of the history of certain countries, so we cannot have a reasonable discussion about recreational drugs. The first requirement would be for the liars (mostly, Prohibition fans) to stop lying, and they aren’t about to stop, because they are True Believers, and when you’ve got True Belief you don’t need any facts.

  118. The researcher (Hurd) says we need to bring more science into the debate, and yet the author paints this study as leaning towards scientific fact rather than a significant discovery. To me, articles like this bastardize science by adding unecessary meaning or opinion. This is how I read the article, and I think a scientific group like National Geographic should be more responsible when reporting science, rather than use it as a headline.

  119. This study is bullshit. How could they not understand cannabis when they have been studying it for years. They just can’t find anything wrong so they make shit up. I’ve smoked pot for most of my adult life and both my children don’t do any drugs. The only reason it is the gateway drug is because it is illegal putting into the hands of dealers who deal heavier drugs. Alcohol is a far more harmful drug and it’s legal. My husband was a stage IV colon cancer victim and smoking pot helped him with the pain and nausea. He would be so sick he couldn’t eat then he would smoke a joint and feel better. I Think he lived longer then he would have without it and certainly had a better quality of life. I think this study was done by an anti-marijuana group. I think of all the vices out there marijuana is the most benign one. You can smoke all night and not overdose. If my kids did do something I would rather them smoke pot then drink alcohol.

  120. Anti pot smear campaign anyone?, Virginia how about we go back to the 1950’s where people use the word “gateway” and women lived in the kitchen? Ah those were the days. Sarcasm aside,
    Your scientific data is biased and obviously DEA funded, nice try but people are smarter than that, and see right through this piece of journalism garbage which you wrote. You say in a previous comment you are pro legalization, however what you wrote completely contradicts what you said. You can’t flip flop like a politician

  121. Proof positive that journalism is subject to manipulation, referencing a study that was done with a methodology whose sole intent was to create fear signifies to me that the journalist was subject to a biased outcome. where is the rhetorical rebuttal from the THC/Cannabidiol side of the house. There were too many questions not asked and answered. For example, Why is big Pharma starting to trademark CBD for pharmaceutical uses? Why is big Pharma lobbying congress to keep Mary Jane on schedule one? I looked up other articles from the author of this one. ie… The Big Sell and It’s Time To Stop Obsessing About the Dangers of Genetic Information. Both articles are well written, a sense of reckless abandon also show in these. Reporting science needs to be done with the same type of methodology that derives results, one sided reporting is nothing more than assumption.

  122. Mrs. Hughes:
    First of all, thank you for your contribution! I understand the hard work that went into creating this article, and I appreciate the effort. However, I would like to point out a few areas of contention:
    To start with, as a few people have already pointed out, human socio-environmental factors are very different from those of rats. These rats were all made to be addicted to heroin, then trained to administer the heroin to themselves. This is clearly going to result in further heroin use, due to a variety of factors such as drug tolerance and behavioral reinforcements. Humans can be (and often are) educated on the cons to heroin use. The issue at hand with this particular bit seems to be that the illegality of marijuana is more of a factor than the marijuana itself – it is the primary function of a drug pusher to sell drugs (I think we can agree at least on that much). With marijuana being an illegal substance, street dealers are the only reliable vector for acquiring marijuana. It is a simple next step, then, for a pusher to convince a marijuana user that ‘heroin is even better,’ or similar. This, to me, would seem to be the major gateway; not the drug itself, but the method of acquisition.
    Second, the idea that the use of marijuana could have epigenetic effects in further generations is almost uselessly redundant. It is a well-known fact that alcoholics, for example, are often descended from other alcoholics. This is due to a combination of behavioral, biological, and genetic factors. There are several studies, according to a cursory search on Google Scholar, that link alcohol as a gateway drug, in addition to cigarettes. Both are currently legal, and both with significantly greater amounts of scientific literature attesting to their harmful effects than marijuana.
    While I have no doubt that your intentions with this article are good, and we definitely are in need of more scientific literature with regards to the effects of marijuana use, this article seems an unintentional bit of fear-mongering. I am loathe to use that term, since I am fairly certain that this was not your intent, but “gateway drug” and “weed” are both clickbaity buzzwords that instantly polarize any group with an opinion on the matter.
    Thank you again for your time and effort!

  123. I’ve been smoking weed (2 to 3 grams/day) for well over 20 years now…I’ve never tried heroin, smack, ice, crack, cocaine, crystal meth etc.

    There is no such thing as a gateway drug…It’s all about the person doing the drugs.

    This study is complete crap!

  124. I have a question i think it logical that what ever u do is giving ur next generation a change in dna but! humans are much larger than a rat! there is no balance in the use of the thc they had! if u give 1 rat 1 joint amout of thc (so like 0.5 gram in my opinion) than how much weed should a human smoke/eat a day?

    a rat is 300 gram
    take me im 85000 gram
    i do 30 minits about 1 joint making and smoking it
    this means i can only smoke 48 a day (no sleeping) and would already been past out becourse i was so stoned

    This mean if u would test this on a human u would give them 283 joints a day
    This is very much and a human will have big smoking troubles

    i do agree u should be clean no drinking smoking bad junk food for few years before start children

    (google fixed it im dutch)
    I have a question i think it logical that what ever u do is giving ur next generation a change in dna but! humans are much larger than a rat! there is no balance in the use of the thc they had! if u give 1 rat 1 joint amount of thc (so like 0.5 gram in my opinion) than how much weed should a human smoke/eat a day? a rat is 300 gram take me im 85000 gram 85000:300=283,333.. i do 30 minutes about 1 joint making and smoking it this means i can only smoke 48 a day (no sleeping) and would already been past out because i was so stoned This mean if u would test this on a human u would give them 283 joints a day This is very much and a human will have big smoking troubles i do agree u should be clean no drinking smoking bad junk food for few years before start children

  125. I have a question, I think it’s logical that what ever you do is giving your next generation a change in DNA! But humans are much larger than a rat! There is no proportional balance in the amount of THC they received! If you give a rat 1 joint’s amount of THC (so like 0.5 gram in my opinion) then how much weed should a human equivalently smoke or consume a day?

  126. So, how much did they pay you Dr. Hurd? By the way, I’ve known a lot of stoners in my life and NONE of them have moved up from pot to do other drugs, and that’s going to be true for most people. And those that do go to other drugs do so because they’re curious or pressured NOT because they smoked pot…

  127. I am willing to bet that if the same study was conducted on substances such as caffeine, tobacco, and alcohol, similar results would be found. Is it just a coincidence that kids tend to drink alcohol before trying weed? Is it okay that commercials of an accepted drug, such as alcohol display commercials on tv with people happy, smiling, and partying with alcohol to have a good time? Every single one of these commercials has an effect on young teenagers, but yet we are concerned with another substance that kids tend to try after getting black out drunk, after feeling the stimulating effects of caffeine and tobacco. Seems to be fairly inconsistent, as people just have it out for thc, or have bias against thc. If alcohol, tobacco, and caffeine are legal, then it should logically follow that thc should be legal too.

  128. I used to love getting your monthly magazine, and since I was 8 I got your kids magazine, always full of interesting facts. Your main thesis was always the world around us and what it looked like. When you themes became too political, too centered on American views I stopped my subscription. I still grab the “Big Yellow” in offices while waiting for meetings. Sadly your point of view has narrowed to something more than American self promotion.
    Now you have waded into the marijuana subject, basing your opinions on lab rats. I stopped reading when this article said lab rats would pick heroin after pot. Somewhere there is a message but how it relates to humans, I cant say. I have smoked pot for almost 50 years, I have raised a healthy family, managed a career and enjoyed smoking pot. The attitude I see in this article reminds me of the brain dead advisors who established that pot and it’s users are bad and should be locked away. Why is it less a crime to shoot someone than to light up a reefer in America?
    How about a study showing how dumb Americans with guns should be treated in mental hospitals for paranoid delusions of self protection.
    This article and alot of your social comment for the last 20 years has been and continues to be right wing verbal diahrrea.

  129. ‘They were more sensitive to novelty, and they self-administered heroin’ – you mean they were smarter?

    Imagine the horrors of performing similar tests with alcohol and nicotine…

    Any negative effects that cannabis may have doesn’t change the fact that the laws preventing its use are corrupt and only in place because it is known to cure many things, and can be grown by anyone.

  130. Did you know brushing your teeth and drinking tap water is worse for you than smoking a lil bit of pot? But why is that not gaining any attention? Hummm…..

  131. Very interesting study, but one particular issue is that it seems like the authors can’t disentangle the effect of rat stress from the psychological effects of cannabis from the actual chemical effects. Rats stressed for other reasons may also have progeny that self-medicate through heroine. Both control and treatment groups were injected (with vehicle solution and THC, respectively), which captures the stress due to injection, but the stress of a rat being “high” is not controlled for. I wouldn’t be surprised at all to find rats in stressed cages have progeny that self-medicate with heroine too. Cannabis could just be a stress initiator. We already know that stress causes changes in DNA methylation.

    Also, there is no mention of reproductive differences between the two classes of rates. Was this investigated?

  132. I like seeing science brought into the conversation of drug use. No matter what the drug, education of what it does, or even could possibly do, is an important factor before you put it in your body.
    That being said, it really shouldn’t have a place in the argument for legalization. I think we can all agree tobacco and alcohol and even most prescription drugs have far more adverse effects on the body than marijuana.
    It’s my body and I should be free to do with it as I please. Science comes into play after, when you make the decision weather you would like to take the risks involved or not.
    Science has it’s place, but it shouldn’t dictate my freedom. If I want to smoke weed, or even shoot heroine or snort cocaine for that matter, I have to deal with the physical consequences it may cause. I shouldn’t have to face jail time for those decisions on top of that.

  133. This is the first time I’ve read an anti-pot paper and not dismissed it as propaganda. I don’t buy the “gateway drug” thing because, to paraphrase one respondent, “If you’re a rat in a cage, why would you not self administer heroin?” and us humans can plainly see the damage caused by opiate abuse. But it would seem to indicate that one should start smoking blunts only after the kids are born. Ironically, that’s probably when your average parent needs it most; after the kids are born and have gone to bed.

    There seem to be a lot of benefits to cannibis consumption and a lot of detriment in our every day lives brought on by environmental pollution and other such unavoidable factors.

    This article does seem to have an alarmist bent, which is why some dismiss it as BS, but it’s a good thing to know.

  134. They need to try this study with CBD and other chemicals in the plant. And also the fact that the rat was not raised by its own mother might be considered a factor. Also I’d like to think that most people are smarter than rats. None the less I think this article was well written and un bias.

  135. Nice to hear unbiased science, but the experiment is flawed because the rats are in boxes.

    In other experiments where rats were given the option to sit in a box taking some hard drug, or going out to play with their friends in a more natural environment, they would choose to go play. For humans it is similar, city life can be dreary, cold, and hostile, and it is easier to sit at home taking drugs than going out to meet a dog-eat-dog world where no one knows their neighbours.

    Finally, it actually seems a little strange for a rat /not/ to self-administer heroin. Perhaps the THC activated their curiosity?

    There are many who got addicted to tobacco through cannabis, so this study may have some relevance, though the mechanism of action is different.

  136. Most of this is pitifully horrible science based on the mistaken notion that correlation = causation. Which is totally wrong and any scientist worthy of being named as one, knows quite well that it’s incorrect.

    The rest is inconclusive – the brains of humans and mice are a bit different and I bet the controls in this study were poor or nonexistent, as they have been in most marijuana studies. It’s almost a prerequisite to get funding.

  137. As I began reading this article I was wondering who funded it!? There in lies where the paranoia comes from!

  138. Too many variables in this study. Looking at people, not rats: Many Heroin users abused pain killers and got hooked that way. There are many people who smoke weed who never did anything stronger-. Societies that have legalized marijuana have not shown pot to be a gateway drug. Does it affect behavior and future generations? yes-what doesn’t? such as all of your drinking in your college days?

  139. There is one major flaw in the way that this research was conducted: they started the study by giving the THC to adolescent mice. It is a well known fact that giving any adolescent a drug of any sort (alcohol, THC, cocaine, etc) does have a severe effect on their subsequent brain development. Heavy alcohol use gives adolescents holes in their brain (frontal lobe and hippocampus if I’m not mistaken); coke and heavy drugs in adolescence increases the likelihood of schizophrenia and other intense mental problems later in life, and pot changes adolescent neuro receptors and brain chemistry in general leading such individuals to seek more mind-altering compounds. The point is that adolescents should NOT be doing drugs; did they investigate similar effects on an adult rat/mouse? Probably not. There’s a reason teens in the US aren’t legally allowed to drink alcohol, and if marijuana was legalized there would probably be similar age restrictions to the buying and consumption of pot unless there was a medical reason (kids can be given opiates or painkillers if they have cancer or other medical/mental problems, so there is an additional parallel here). In addition, in the US we do have a habit of giving mind-altering compounds such as aderrol and other psychiatric drugs to children, and I haven’t seen any stories about how that effects their subsequent genetic structure. If there were age restrictions on the buying and consumption of THC, then the study mentioned is practically useless because the authors of the study (at least, from what your article mentioned) only investigated the effects on mice introduced to THC in their adolescence. What is the effect if introduced after adolescence? That is where the bureaucratic paranoia factor comes in to play; why wasn’t a similar question about the effect on a grown-up brain posed? Do rodents live long enough to do such a comparative study and if they don’t, then why are they models for a question such as this? Without such an inquiry, the question posed about the effects of pot on subsequent generations genetic structures has yet to be answered, and this study, although interesting, only proves that teens should not be introduced to drugs until after their brains are more fully developed.

  140. One of the reasons people are having a fit about this article is your title “A Gateway Drug Across Generations”. The term gateway drug is a drug war propaganda term that implies that using one substance will lead to the use of other more severe substances. If you had just titled the article “New research shows possible generational effects of marijuana usage” you wouldn’t have had nearly as much backlash.

  141. It is sad to see such a poorly written article be published by National Geographic. Maybe the reason it was published here, though, instead of a peer reviewed science journal is because the way a lot of different facts are hung together simply don’t follow any kind of logic other than to promote the preconceived notions of a school girl.

  142. just legalize it already. people will smoke it anyway.

    its time. let me decide if i want to use it or not. I’m a big boy i know the risks etc etc.

    the same thing could be said for tobacco, alcohol, caffeine. so be consistent its not special or any more or less dangerous. its my body, buzz off

  143. “Just as they did in previous studies, Hurd’s team gave male and female rats periodic injections of THC throughout their adolescent period. This pattern of exposure is meant to mimic the typical pot-smoking teen. ‘Every few days they got about a joint’s worth of THC,” Hurd says.'”

    Assuming a joint’s worth of THC does not refer to a scaled-back amount corresponding to rat weight (accessing the methods requires a subscription), then a 2 lb rat receiving a joint’s worth every other day would be roughly equivalent (similar to LD50 scaling) to a 150 lb human teenager consuming 75 joints every 48 hours. Calculating by brain weight instead of body mass is even more pronounced. Rat brain = 2 g, Human brain = 1,400 g. Using this ratio a human teenager would need to consume 700 joints every 48 hours for equivalent exposure.

  144. Thanks for an interesting article, Virginia. You do good work. In the immortal words of Sandra Boynton on a greeting card, “Don’t let the turkeys get you down.” I have to agree with one commenter that the evidence from most of these comments suggests that long term cannabis use does result in a near total loss of the ability to think or write clearly.
    For more substantive evidence, see this:

    Persistent cannabis users show neuropsychological decline from childhood to midlife

  145. Preston Garrison:

    ” I have to agree with one commenter that the evidence from most of these comments suggests that long term cannabis use does result in a near total loss of the ability to think or write clearly.”

    Stereotype much? You assume a lot. And you know what they say about assumptions, right?

  146. Firstly. I think the explanation of how the studies were done, is either incomplete, or it was done totally wrong. Secondly. Having done experiments on animals that are harmful to the animals, and are actually supposed to predict influences on humans are incredibly stupid to undertake. Suggesting that the scientist(s) trying to prove the negative effects of marijuana are actually morally deviant themselves, and are actually getting funding for their research by someone that would find benefit from these experiments. This said, Go sell your bullsh!t somewhere else.

  147. WTF does National Geographic have to do with “drug” usage anyway. What about the abuse of “legal” drugs and/or their effect on offspring, or superbug resistance? Your magazines are a waste of good paper; if you really cared you’d shutter the whole company and go home.

  148. I hav seen 1st hand the medical benefits of marijuana so im more inclined to trust the outcome based approach than the evidence based approach. As far as long term usage…what constitutes long term usage? People have been smoking weed for decades without any apparent health issues. I personally dont understand the reasons why marijuanna is still illegal in most countries when alcohol which is legal causes waaaaay more damage…which has been proven!!! Yet its legal…makes no sense… some become violent; some become depressed; liver cancer; cirhosis eosophageal cancers; stomach cancer etc etc. If alcohol is legal marijuana should be to. Right?

  149. The very fact that the journalist says: “But just how risky is it? Scientists are only beginning to figure that out,” speaks volumes.

    Here is a drug that has been used by hundreds of millions of people worldwide for thousands of years and she is suggesting scientists are ‘only now beginning to find out’ the risks….Does that figure?

    Take a new drug like mephedrone (M-CAT); we knew about the risks of mephedrone within months of it appearing on the streets. Or take an established drug like cocaine; we have known about the risks of that for generations.

    So its not as though scientists have been blind to some ‘hidden risks’ of cannabis that are only now emerging. If cannabis was a seriously harmful drug that would have been well apparent by now.

    Truth is, from an epidemiological point of view, cannabis is remarkably safe. Not 100% safe (nothing is, especially not poorly written journalism), but remarkably safe – and certainly not worthy of a totally prohibitionist stance.

    Those in favour of cannabis prohibition are now clutching at straws. They recognise they have lost the argument on grounds of health risks (it is relatively safe – indeed beneficial for many people), crime (prohibition clearly increases crime and social problems – not solves them) and finance (the ridiculous costs of prohibition are undeniable).

    The only front they have left is moral grounds – and that is very shaky indeed. Because if we are going to deny adults’ right to smoke cannabis purely on moral grounds then we first need to look at prohibiting a whole load of other things: pornography, fishing, boxing, meat eating etc etc – and no one is seriously suggesting we do that.

    Dr Ben Sessa
    Substance Misuse Psychiatrist, UK

  150. The comments, as usual, were pretty amusing, in a sad way. I was going to say, this is the consequence of the War On Science being waged today, except that here in the US, dogmatic ignorance has always been a proud tradition. Note that “I don’t like the conclusions I think the article comes to” isn’t much of a valid argument, especially when you don’t even know what those conclusions are. Anyway, all the various silly “You’re stupid and this article is wrong and I hate you all!” comments are good in their own special ways, but I think I like Brent’s comment the best:
    “This article is radically wrong and the author is not a journalist. Don’t be fooled–inform yourself on the issue by visiting Wikipedia:”
    I was laughing for a good ten minutes after reading that.
    I’m guessing that other than Virginia and a couple other folks, nobody actually bothered to read the study itself; it’s just so much easier simply to leap about yelling how bad it was. Even juggalos can do that much.
    Interesting stuff, Virginia, but I’m still uncertain about how much there is to the epigenetics fad. There’s probably some good and important stuff there, but it’s early days yet. Keep the articles coming!

  151. Naturally, I haven’t read all the comments – who has time. But one issue I have with these controlled studies is how they often fail to even address similar contexts in the real world. Specifically, there are quite a few cultures (outside N. America) that have used cannabis for untold generations. I’ll refer you to the Jamaican studies (Dreher). The problem in ignoring these & then asserting cannabinoids cause brain damage is to racially imply some diminished intelligence in these other people as the generations progress. An anthropologist, ethnologist, or ethnobotanist should be addressing these real-life samples by conducting a number of intelligence tests, physiological analyses, as well as applying other useful comparative tools. http://www.420magazine.com/forums/medical-marijuana-facts-information/79428-drehers-jamaican-pregnancy-study-print.html

  152. @JohnR.
    There is NO NEED to actually read the article when hundreds of years of empirical evidence exists. Actually, for that matter, there is not even a need for the study in the first place….

  153. As a parent of two teens who have parents who are both in recovery from alcohol and cannabis addictions, I am interested in the science. My cannabis addiction was greater than alcohol, and my kids’ Dad is still smoking weed after 35 years (and denying it to his kids; and trying not to but failing), so from my own personal experience, I can definitely say that it can become an addiction, especially for people who are pre-dispositioned. If alcoholism is somehow passed along genetically (this has got to be fact by now), why not cannabis? I am happy to read the article and I am glad it is being studied. Knowledge is power. We all have choices. Thanks Virginia.

  154. These drug proponents are kidding themselves. Visit an AA meeting and see how many “happy” people are there. Your life should make you happy, not your avoidance of life.

    1. @Kerry VerMeulen….What on earth does AA have to do with this? We are talking about Marijuana, NOT alcohol..there is a Massive difference!

  155. I’d never considered a biological mechanism for the gateway drug claim before. My understanding of it was always that using one illegal drug removed inhibitions against breaking drug laws in general, while also providing opportunities to buy other drugs from a dealer (and in some places that might be possible, but my experience has been that most pot dealers don’t sell other drugs).

    There is also a claim that once a person tries one drug, they might become bored with it and seek other substances with a stronger effect.

    Essentially, before now this argument of “gateway drug” was always sociological or psychological in nature, not biological.

    That said, I’ll report my own anecdotal experience knowing the grandchildren of a number of pot smokers who aren’t using or abusing any illegal substances as far as I can see. In fact, the vast majority of pot smokers I know of don’t venture into anything harder than an occasional psychedelic mushroom trip (perhaps 99%, and I’ve met a lot over the years). From everything I know, there’s little merit to any of the gateway drug theories.

    The vitriol in many of the comments here is uncalled for. Please don’t let it discourage you from following up on this story.

  156. Bad science which is obviously designed to justify a B.S. phrase like “Gateway Drug” causes brain damage in the self rightious. That damage not only effects the future offspring of those who listen to it; it damages entire generations affected by them.

  157. What a dishonest little article.

    Has any other drug received half the scrutiny marijuana has? Any of the drugs that make your sponsors a lot of money every year, killing the occasional patient here and there?

    Marijuana has the potential to be the most medicinally useful plant on this planet. No wonder your sponsors want to keep it illegal, and to spread rumours about it being potentially dangerous. Without providing any actual evidence of harm, because there isn’t.

    Shame on you.

  158. This research did not study the effects of marijuana on adolescent rats, but rather the effects of trauma – they were forcibly given a dose of a perception-altering drug, every few days, which is bad enough.

    I’d like to stress this point: choice versus being forced. Like the difference between having sex and being raped: same activity, such a different psychological impact.

    “Just as they did in previous studies, Hurd’s team gave male and female rats periodic injections of THC throughout their adolescent period. This pattern of exposure is meant to mimic the typical pot-smoking teen. ‘Every few days they got about a joint’s worth of THC,’ Hurd says.”

    What’s a joint’s worth? How does it translate to micrograms/Kg of body mass? ‘Just as they did in previous studies’ – this may serve as a clue. In previous studies of marijuana rats were injected with incredibly high doses of synthetic THC, which is a lot stronger than the natural THC. In addition, THC, when administered alone, tends to cause anxiety and other unpleasant effects. Natural marijuana contains many additional compounds, one of which – cannabidiol – counteracts those effects of THC.

    So they forced adolescent rats to endure this abuse, every few days…. no wonder they ended up being traumatized. Hence their propensity towards heroin abuse, hence the brain abnormalities.

    The fact that Mrs. Hughes either failed to see that this was bad science or chose not to, reflects very poorly on her scientific skills and on her personal integrity.

  159. the greatest plant in the universe is almost free, LET FREEDOM RING! 13

    i expect much better from NAT GEO, wow, how the mighty have fallen

    Senator Kimberly Yee of Arizona is denying a marijuana research bill for vetarans, she should be jailed

    “any doctor against marijuana is a doctor of death” – cali secret 420

    from 0 states to half the country, from low 20% approval to almost 70%, cali runs this planet by 2 decades, time to tie marijuana to the 2014, 2016 elections, out with the old, in with the new

    20 years behind us southern states, sad and scary….nobody denies freedoms like the south, nobody…the top ten incarcerators on the planet are southern states…even if marijuana reforms did pass the republiCANTS in charge would deny you all your freedoms, centuries of practice…no matter though, we never planned on getting your backwards brethren from day one, half the country already but not one southern state, lol…not 1….my turn, I gave you 20 years, watch and learn

    Deaths by Alcohol and Tobacco: Millions
    Deaths by Prescription Drugs: Quadrupled in last decade
    Deaths by Guns: Millions
    Deaths by Marijuana: 0, ever…they are killing my American family while denying freedom

    love and freedom forever


  160. The entire experiment/article must be considered flawed,and therefore invalid,as it is a well known SCIENTIFIC fact that THC,CBD’s and CBN’s require a MINIMUM of 30 days to even begin to leave the fat cells (where these chemicals lodge), so to wait a ” few weeks” to begin any testing is pointless,erronious,misleading and very irresponsible for any “professional” who considers themselves a “scientist”,much less a “professional” by any standard.Shame on you.

  161. marijuana is one of the most controversial topics becasue its benefits and harms manage to cancel eachother out, so its great to see such a thorough study analysing the effect on the neurology, since brain synapses at the end of the day are the most strongly contributing factor to our consciousness. although it is impossible to conduct any conclusive study, science is change in nature, its good to see a study that takes apart its effect on receptors, but maybe this can also be used to test its positive effects.

  162. It’s interesting to read all of the ‘pro-marijuana’ flavored posts in reply to this article. I really appreciated this article and it’s exposure of some very interesting questions. I think people are far more concerned with the legality of a known recreational hallucinogen and less with the implications of this study. It definitely brings up enough red flags to warrant more research and study into the long term and, what I feel is the most important portion from this article, possible cross-generational effects of THC. Could your future children sue you for smoking marijuana if they are negatively impacted mentally or physically due to voluntary genetic malice you inflicted upon them?

    What an exciting can of worms this is.

  163. Curious about the effect of cocaine exposure in rats leading to decreased cocaine use in their offspring. The way you’ve spun the THC research — “Weed – a gateway drug across generations?” would’ve been spun, for the cocaine study, as “Cocaine — a preventative solution for hard drug addiction across generations?”

    I do agree that this research should be discussed, disseminated amongst lay audiences, but I really worry that you’re scaring parents (including our very Barack Obama!) that their prior use of marijuana is putting their kids at risk for heroin addiction. You’re a scientist yourself, and an excellent writer, so you wield a double-edged sword: you understand the logical limitations of any given scientific study, but are capable of producing convincing rhetoric about those studies. Might be useful to keep the framing of such findings conservative, especially when the topic is so emotionally charged (and prone to misinterpretation by your non-science audience). With that said, I appreciate the article, and I am dismayed at the frantic response you’ve incurred from the pro-pot community.

  164. I don’t smoke pot or have any plans to smoke it. Virginia I think if you compare what legal drugs that are being used by people and compared that to pot that even if pot did what the so called rat test says it did that those side effects would be mild compared to the damages that legalized pain meds cause. I’ve know people that have smoked pot in their teens that stopped once they got jobs and became adults. Most people on prescription pain pills can not stop as they become addicted to them. I don’t know anyone that has gone deaf because of using pot. Studies have shown if a parent is addicted to drugs or booze their kids are predisposed to the same and on down the line genetically. I’m not so sure I believe that but that’s what studies claim. I know quite a few people who’s parents were drunks or druggies and the kids didn’t get hooked on it. I’ve never used legal pain meds either so I have no clue all the bad things they do but just the little bit I do know it very well could be that pot has less side effects then what the FDA has already approved.

  165. so in other words you are comparing us to rats. And why not legalize pot it has the same effects as aderale the medicated drug to help with ADHD or ADA it has to long term effects or down falls.. Austin Turner From Crittenden ky

  166. Are you sure this study wasn’t testing for effects on the brain when rats are effectively adopted by an involuntary adoptive mother? We know that rats’ brain development is deeply affected by how they are nurtured. Was there a control group of rats used that were raised by their own THC-exposed biological parents? A control group of rats whose biological parents weren’t exposed to THC who were also raised by a non-biological mother?

  167. i was a daily smoker from when i was 17 to shortly before present, am 25, i am a successful inependent contractor, and i’m pretty sure that marijuana/cannabis is what helped me develop the work ethic I have and still maintain, but it also could very well be that i had a poor (financially) upbringing and rebelled in school because i would often correct my teachers, i dropped out my senior year and have been working since, i feel that there are too many variables that prevent empirical finding on long term effects. all i kknow for sure is that cannabis took me from being a kid that did nothing but playing videogames and being a shitty person, through its modification of my core values and how i applied them to interactions with people,

  168. Of course close to 80% of heroin users started with marijuana. But I would bet that almost 100% started with alcohol, a drug that also affects one’s offspring.

  169. Where are the double blind studies showing any of this?
    I really have a hard time with a government that lies to its people for 70 years people in this country have been using marijuana where are the dead? Where is the lung cancer? Where is any evidence not tainted by the drug war? It really should cause one to wonder why law enforcement and illegal growers both want marijuana to stay illegal. If you want a gateway drug how about milk? Did we not see how many are dead due to coffee,sugar and legal drugs? Where is the concern for the dead do to big pharmaceutical? We have the highest incarnation rate in the world. Maybe we Ned to stop calling ourselves the land of the free. Since the government will not allow any study the tries to show medical use how can we trust the science. What ever your position on medical marijuana don’t you think that locking people up for life for marijuana is more harmful the the plant itself. It is very hard to separate hype from fact when all we get is lies and lopsided research. Oh and if you did not know it the US government holds a patent on medical marijuana while at the same time they say it has no medicinal use. The punishment does not fit the crime. And there are people who have benefit from it. Something that belongs between a patient and their Dr. And if dependant does it not belong in medical hands and not law enforcement. Prohibition has no place in a free society. Way passed time to end it.

  170. As a stakeholder of this discussion, I’ve decided to come out from lurking to bury this argument. Virginia, the basis of this article was 100% spot-on, there is a lack of research in regards to the overall effects of Cannabis. The “gateway effect” however, has been attributed to political fear tactics in the past (“Reefer Madness”) as well as the slippery-slope fallacy of logic (THC consumption leads to increased chance of heroin use). Opinions are entirely out of this discussion from here on, I’ll let you connect the dots. Mind you, the lack of consistent empirical experimentation of this subject is gargantuan. That’s thanks to the the fact that marijuana is still federally illegal. This turns off research in nearly all of federally-funded institutions right off-the-bat (even in the “legal” states). This gives the Feds control over a good number of the studies that get published. The paper you reported on (“http://www.ncbi.nlm.nih.gov/pubmed/24385132”:link here) was written by the National Institute on Drug Abuse (NIDA). Here is a link to their website (http://www.drugabuse.gov/:NIDA). NIDA is a United States federal-government research institute whose mission is to “lead the Nation in bringing the power of science to bear on drug abuse and addiction.” There’s a second journal provided by this same source, nearly identical to the one provided here, which was also written by Hurd, and was also funded by the same government organization (NIDA). Hurd as well as the other authors of these journal entries demonstrate a political bias simply within the abstract. They state “Most of the debates and ensuing policies regarding cannabis were done without consideration of its impact on one of the most vulnerable population, namely teens, or without consideration of scientific data.” Here is the website of the Colorado Marijuana Initiative – a group of policymakers and stakeholders that passed A.64 in CO (“http://www.regulatemarijuana.org/marijuana-vs-alcohol”:Shown here). I also decided to include a link to the Marijuana Policy Project (another group of policy makers and stakeholders) “www.mpp.org/assets/…/GatewayDebunked.pdf”:here. All in all, these scientific findings are entirely contradictory. No long term scientific evidence _means_ no long term scientific evidence.

  171. OK, it’s interesting. Now would you care to publish a piece debunking the myriad B.S. studies that have underpinned our irrational fear of cannabis since the 1960’s?

    No? That’s OK, I’m sure the thousands upon thousands of families destroyed by so-called “scientific” misinformation and propaganda don’t mind. I’m sure the billions of wasted dollars isn’t a problem. I’m sure the cartels appreciate it.

  172. Good read on the whole ‘gateway theory’ propaganda –http://www.theatlantic.com/health/archive/2015/04/the-real-gateway-drug-isnt-marijuana/391266/?utm_source=SFFB

    Take away point: playing with data to influence social perception is fun fun fun!

  173. so when can we expect to see control studies for parents that pray or meditate and how this affects your children?

    how far into the future this factor might contribute to the possible well being of our future generations?

    by the way I am not religious

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