# Does marijuana stunt brain development in youth? **URL:** \ **Category:** Factual Questions\ **Created:** [August 2, 2005, 8:55am UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278 "2005-08-02T08:55:21Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Trapp](https://avatars.discourse-cdn.com/v4/letter/t/ba9def/32.png) [@Trapp](https://boards.straightdope.com/u/Trapp)\ **Post date:** [August 2, 2005, 8:55am UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/1 "2005-08-02T08:55:21Z")
Does marijuana stunt brain development in youth?, I’ve heard many articles suggesting that it does, but I haven’t seen any solid proof. So I am wondering, what do you guys think? ---
**Author:** ![MAGunter](https://avatars.discourse-cdn.com/v4/letter/m/a87d85/32.png) [@MAGunter](https://boards.straightdope.com/u/MAGunter)\ **Post date:** [August 2, 2005, 9:02am UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/2 "2005-08-02T09:02:54Z")
Define youth? ---
**Author:** ![Busy\_Scissors](https://avatars.discourse-cdn.com/v4/letter/b/d78d45/32.png) [@Busy\_Scissors](https://boards.straightdope.com/u/Busy_Scissors)\ **Post date:** [August 2, 2005, 10:15am UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/3 "2005-08-02T10:15:54Z")
> [@Trapp](#): > > Does marijuana stunt brain development in youth?, > > I’ve heard many articles suggesting that it does, but I haven’t seen any solid proof. So I am wondering, what do you guys think? No way man, the weed makes your brain grow! Be careful though, if you’re hitting the weed hard you’ll need an extra-big cranium to accommodate your new enormous brain. ---
**Author:** ![Trapp](https://avatars.discourse-cdn.com/v4/letter/t/ba9def/32.png) [@Trapp](https://boards.straightdope.com/u/Trapp)\ **Post date:** [August 2, 2005, 10:46am UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/4 "2005-08-02T10:46:57Z")
Umm kids ages 12 13 or 14… ---
**Author:** ![Trapp](https://avatars.discourse-cdn.com/v4/letter/t/ba9def/32.png) [@Trapp](https://boards.straightdope.com/u/Trapp)\ **Post date:** [August 2, 2005, 11:17am UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/5 "2005-08-02T11:17:53Z")
bump… ---
**Author:** ![Lissa](https://avatars.discourse-cdn.com/v4/letter/l/85f322/32.png) [@Lissa](https://boards.straightdope.com/u/Lissa)\ **Post date:** [August 2, 2005, 2:51pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/6 "2005-08-02T14:51:42Z")
Personally, I think a lot of those studies contain fundamental attributional errors. It’s like the old _Law and Order_ quote: If we find that ninety percent of juvenile delinquents chew gum, do we conclude that gum-chewing leads to crime? Kids who choose to smoke weed while still in school (to the point where it affects their lives) may be kids who already aren’t exactly Rhodes Scholars. There are a lot of environmental factors which contribute to intelligence. Kids who don’t have a strong, dedicated set of parents who are concerned about their child may naturally gravitate toward groups in which marijuana use is a part of recreation. Kids who are bright, energetic and motivated often don’t have _time_ to sit around and get stoned all the time. They may smoke at a party, but their day-to-day lives are to busy with study, and extra-curricular activities to spend much time goofing off. Kids who aren’t super-bright to begin with and who suffer from casual neglect by the parents have more time to become “stoners.” Since those kids may never have been properly stimulated or socialized to begin with, that could account for the difference in overall intelligence. ---
**Author:** ![Camus](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@Camus](https://boards.straightdope.com/u/Camus)\ **Post date:** [August 2, 2005, 4:28pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/7 "2005-08-02T16:28:05Z")
> [@American Academy of Pediatrics](#): > > Clearly, young people who are frequent users of marijuana experience residual neuropsychologic effects with an impaired ability to learn. > > An “amotivational syndrome” has been described in chronic heavy marijuana users. This syndrome is characterized by the inability to sustain attention on environmental stimuli and to maintain goal-directed thinking and behavior. An additional source of concern is the occasional occurrence of dysphoric reactions that may range from mild fear to depersonalization to frank paranoia. [http://www.rvpi.com/AAP/Marijuana.htm](http://www.rvpi.com/AAP/Marijuana.htm) Given that adolescent brains are still developing around the ages of 12-15 and on, impairing the limited abilities they have at the time doesn’t seem like a good idea. Plus, heavy marijuana use has been shown to be associated with impotency and decreased sperm levels and motility. All these talking heads have been going about the anti-drug routine all wrong. Instead of focusing on how it could effect their brains, they should just be talking about how it could effect their dorks. ---
**Author:** ![II\_Gyan\_II](https://avatars.discourse-cdn.com/v4/letter/i/bbe5ce/32.png) [@II\_Gyan\_II](https://boards.straightdope.com/u/II_Gyan_II)\ **Post date:** [August 2, 2005, 5:31pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/8 "2005-08-02T17:31:06Z")
Let’s get some real studies in this discussion. [Current and former marijuana use](http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=11949984): preliminary findings of a longitudinal study of effects on IQ in young adults > [@](#): > > Using data from a group of young people whom we have been following since birth, we examined IQ scores before, during and after cessation of regular marijuana use to determine any impact of the drug on this measure of cognitive function. > … > We then compared the difference in IQ scores of current heavy users (at least 5 joints per week), current light users (less than 5 joints per week), former users (who had not smoked regularly for at least 3 months) and non-users (who never smoked more than once per week and no smoking in the past two weeks). > … > Current marijuana use was significantly correlated (p \< 0.05) in a dose- related fashion with a decline in IQ over the ages studied. The comparison of the IQ difference scores showed an average decrease of 4.1 points in current heavy users (p \< 0.05) compared to gains in IQ points for light current users (5.8), former users (3.5) and non-users (2.6). [Neurocognitive consequences of marihuana](http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T9X-4F085FN-1&_coverDate=04%2F30%2F2005&_alid=300988231&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5126&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=17aeaf8d1cdac79b7589295fbdd19669) : a comparison with pre-drug performance > [@](#): > > The present study examined effects of current and past regular use of marihuana in subjects for whom pre-drug performance had been ascertained in a prospective, longitudinal fashion. A total of 113 young adults, assessed since infancy, were evaluated using neurocognitive tests for which commensurate measures were obtained prior to the initiation of marihuana smoking. > … > Marihuana users, determined by urinalysis and self-report, were categorized as light(\<5 joints per week) and heavy (≥5 joints per week) current users and former users, the latter having used the drug regularly in the past (≥1 joint per week) but not for at least 3 months. > … > current regular heavy users did significantly worse than non-users in overall IQ, processing speed, immediate, and delayed memory. In contrast, the former marihuana smokers did not show any cognitive impairments. It was concluded that residual marihuana effects are evident beyond the acute intoxication period in current heavy users after taking into account pre-drug performance but similar deficits are no longer apparent 3 months after cessation of regular use, even among former heavy using young adults. ---
**Author:** ![Metacom](https://avatars.discourse-cdn.com/v4/letter/m/ecae2f/32.png) [@Metacom](https://boards.straightdope.com/u/Metacom)\ **Post date:** [August 2, 2005, 5:46pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/9 "2005-08-02T17:46:50Z")
Interesting, **II Gyan II**. Light marijuana use appears to improve IQ: > [@](#): > > gains in IQ points for light current users (5.8) And use in general doesn’t reduce IQ: > [@](#): > > We conclude that marijuana does not have a long-term negative impact on global intelligence. Maybe we should start including a joint in the federal brown-bag lunches on Monday, Wednsday, and Friday? 🙂 ---
**Author:** ![chaoticbear](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)\ **Post date:** [August 2, 2005, 6:52pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/10 "2005-08-02T18:52:11Z")
Let’s see. My first time using it was in 8th grade, when I would have been _counts on fingers_ barely 13. I continued to use it (at the rate of about a quarter of an ounce every two weeks) through 11th grade, and a little at the beginning of my senior year. If it stunted my brain development, I haven’t noticed. ---
**Author:** ![II\_Gyan\_II](https://avatars.discourse-cdn.com/v4/letter/i/bbe5ce/32.png) [@II\_Gyan\_II](https://boards.straightdope.com/u/II_Gyan_II)\ **Post date:** [August 2, 2005, 7:13pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/11 "2005-08-02T19:13:20Z")
> [@chaoticdonkey](#): > > If it stunted my brain development, I haven’t noticed. Well, it stunted the self-observation module. j/k ---
**Author:** ![II\_Gyan\_II](https://avatars.discourse-cdn.com/v4/letter/i/bbe5ce/32.png) [@II\_Gyan\_II](https://boards.straightdope.com/u/II_Gyan_II)\ **Post date:** [August 2, 2005, 7:14pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/12 "2005-08-02T19:14:55Z")
> [@Metacom](#): > > Interesting, **II Gyan II**. Light marijuana use appears to improve IQ: Or, smarter people learn to see through the propaganda and aren’t afraid to use pot, but don’t go to the other extreme. ---
**Author:** ![Camus](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@Camus](https://boards.straightdope.com/u/Camus)\ **Post date:** [August 2, 2005, 7:24pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/13 "2005-08-02T19:24:18Z")
> [@II Gyan II](#): > > Or, smarter people learn to see through the propaganda and aren’t afraid to use pot, but don’t go to the other extreme. Why does brain development automatically equal IQ scores? Few, if any, reasonable people have ever seriously claimed that drugs of any kind actually made people more stupid in terms of actual knowledge. Instead, most people who think drugs affect intelligence seem to come to that conclusion by other factors such as the ability to learn something new quickly, process multiple pieces of information, and retain that information. All of these things don’t necessarily implicate intelligence but they do implicate brain development. Which is not to say that light pot smoking does any of these things, as everyone’s unique brain chemistry and unique smoking habits make it impossible for any doctor to predict exactly how much pot it would take to permanently damage someone’s brain. But saying that pot does have negative side-effects isn’t exactly propaganda. Lumping pot in with heroin as a hardcore drug is propaganda. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [August 2, 2005, 7:56pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/14 "2005-08-02T19:56:25Z")
Size 9, thank you. ---
**Author:** ![II\_Gyan\_II](https://avatars.discourse-cdn.com/v4/letter/i/bbe5ce/32.png) [@II\_Gyan\_II](https://boards.straightdope.com/u/II_Gyan_II)\ **Post date:** [August 2, 2005, 8:26pm UTC](https://boards.straightdope.com/t/does-marijuana-stunt-brain-development-in-youth/315278/15 "2005-08-02T20:26:37Z")
> [@Camus](#): > > most people who think drugs affect intelligence seem to come to that conclusion by other factors such as the ability to learn something new quickly, process multiple pieces of information, and retain that information. Intelligence is an imprecise and crude measure of those activities. Everything alters the brain, from food to books to video games to drugs. What is relevant is how these changes affect function, which is where psychometric testing comes in. > [@](#): > > But saying that pot does have negative side-effects isn’t exactly propaganda. It’s not propaganda if given with context. Everything can have bad side-effects, depending on circumstances, including water, sugar, fat, alcohol, pot. But that’s missing the point, which is that pot is not unique in having side-effects. However, that’s how govt. messages treat pot, as a special insidious substance. It’s not propaganda if you say that “heavy pot smoking may lead to cognitive deficits”. It becomes propaganda when that context is removed and the messages are vague and deceptive like “pot smoking may lead to cognitive deficits”, which is like saying that “eating fast food may lead to obesity”. And that’s what the govt. essentially does. It won’t lie outright, since in today’s media saturated and litigation-friendly world, getting caught lying will dissolve any credibility, but what they will do, is write technically truthful statements, which, nonetheless are lies in spirit. Statements, which are informed by psychology, to elicit the intended response, even if the literal reading of the message does not carry that connotation. Somewhat like advertising.