# New UCSD study on marujuana: not harmful? **URL:** \ **Category:** Great Debates\ **Created:** [June 29, 2003, 6:45am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115 "2003-06-29T06:45:02Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Beagle](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Beagle](https://boards.straightdope.com/u/Beagle)\ **Post date:** [June 29, 2003, 6:45am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/1 "2003-06-29T06:45:02Z")
[Here](http://health.ucsd.edu/news/2003/06_27_Grant.html) it is. I could cite all the anti-drug websites, but I’m assuming you know what they all have to say. Basically, the opposite. > [@](#): > > An analysis of research studies with long-term, recreational users of marijuana has failed to reveal a substantial, systematic effect on the neurocognitive functioning of users. According to researchers at the University of California, San Diego (UCSD) School of Medicine, the only deleterious side effect found was a minimal malfunction in the domains of learning and forgetting. > > The findings were particularly significant considering the movement by several states to make cannabis (marijuana) available as a medicinal drug, and questions regarding its potential toxicity over long-term usage. > > Published in the July issue of the Journal of the International Neuropsychological Society, the study involved a quantitative synthesis of 15 previously published research studies on the non-acute (residual) effects of cannabis on the neurocognitive performance of adult human subjects. > > The studies included 704 long-term cannabis users and 484 non-users. The neurocognitive performance measurements included simple reaction time, attention, verbal/language, abstraction/executive functioning, perceptual/motor skills, motor skills, learning and forgetting. > > “Surprisingly, we saw very little evidence of deleterious effects. The only exception was a very small effect in learning new information,” said Igor Grant, M.D., the study’s senior author, a UCSD professor of psychiatry, and director of the Center for Medicinal Cannabis Research (CMCR), a collaborative, state-supported program between UCSD and UC San Francisco, that oversees 11 studies of the safety and efficacy of medicinal cannabis to treat certain diseases. > > In describing the negative effects in the study, the research team said the problems observed in learning and forgetting suggest that chronic long-term cannabis use results in selective memory defects. They added that “while the results are compatible with this conclusion, the effected size for both domains was of a very small magnitude.” > > Grant added that the minimal side effects seen “raised the question of practical significance. If we barely find this tiny effect in long-term heavy users of cannabis, then we are unlikely to see deleterious side effects in individuals who receive cannabis for a short time in a medical setting.” > > **In addition, Grant said that heavy marijuana users often abuse other drugs, such as alcohol and amphetamines, which also might have long-term neurological effects. This raises the question of the extent to which the other drugs contributed to the minimal problems found in learning and forgetting in the marijuana users.** (bolding mine) This last paragraph had me screaming “I told you so!” Back in the 1980s, as a college debator, I found evidence from the Harvard Medical School which indicted many drug studies–supposedly on marijuana–which included multiple substance abusers. In other words, the old studies took multiple drug abusers and linked every noted effect to every drug they took. Of course, back then there wasn’t any governmental pressure to arrive at a certain result. :dubious: What’s the straight dope? Sorry, bad double pun. ---
**Author:** ![Beagle](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Beagle](https://boards.straightdope.com/u/Beagle)\ **Post date:** [June 29, 2003, 6:48am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/2 "2003-06-29T06:48:49Z")
Um, its effects on spelling in thread titles are as yet undetermined. :o Would a mod. mind fixing that? ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [June 29, 2003, 7:00am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/3 "2003-06-29T07:00:57Z")
> [@](#): > > “Surprisingly, we saw very little evidence of deleterious effects. The only exception was a very small effect in learning new information,” The study doesn’t say weed isn’t harmful, it says it doesn’t cause a lot of long-term brain damage. ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [June 29, 2003, 8:01am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/4 "2003-06-29T08:01:02Z")
You see, the thing about weed is…um…what was I talking about again? ---
**Author:** ![Zoe](https://avatars.discourse-cdn.com/v4/letter/z/a4c791/32.png) [@Zoe](https://boards.straightdope.com/u/Zoe)\ **Post date:** [June 29, 2003, 8:05am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/5 "2003-06-29T08:05:05Z")
Welcome, Diogenes! \ ---
**Author:** ![Brutus](https://avatars.discourse-cdn.com/v4/letter/b/91b2a8/32.png) [@Brutus](https://boards.straightdope.com/u/Brutus)\ **Post date:** [June 29, 2003, 8:13am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/6 "2003-06-29T08:13:29Z")
Do you really think that ‘They’ would have made an entire movie about reefer, and its associated madness, if there weren’t all sorts of negative effects to taking pot? ---
**Author:** ![I\_Love\_Me\_Vol.I](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/i_love_me_vol.i/32/521_2.png) [@I\_Love\_Me\_Vol.I](https://boards.straightdope.com/u/I_Love_Me_Vol.I)\ **Post date:** [June 29, 2003, 8:24am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/7 "2003-06-29T08:24:14Z")
Brutus-- I can only hope you are joking… You ARE joking… right? ---
**Author:** ![Ben\_Hicks](https://avatars.discourse-cdn.com/v4/letter/b/bbce88/32.png) [@Ben\_Hicks](https://boards.straightdope.com/u/Ben_Hicks)\ **Post date:** [June 29, 2003, 12:27pm UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/8 "2003-06-29T12:27:53Z")
Did someone say Snickers? I’ve got the munchies _baaaaad_ ---
**Author:** ![CarnalK](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnalk/32/486_2.png) [@CarnalK](https://boards.straightdope.com/u/CarnalK)\ **Post date:** [June 29, 2003, 1:41pm UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/9 "2003-06-29T13:41:13Z")
That jibes with a long term study released by the Canadian Medical Association a year ago: > [@](#): > > Interpretation: Current marijuana use had a negative effect on global IQ score only in subjects who smoked 5 or more joints per week. A negative effect was not observed among subjects who had previously been heavy users but were no longer using the substance. We conclude that marijuana does not have a long-term negative impact on global intelligence. Whether the absence of a residual marijuana effect would also be evident in more specific cognitive domains such as memory and attention remains to be ascertained. from: [CMAJ link](http://www.cmaj.ca/cgi/content/full/166/7/887?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&titleabstract=marijuana&searchid=1056894035124_375&stored_search=&FIRSTINDEX=0&journalcode=cmaj) And you won’t get the munchies if you eat a decent meal before you smoke. (or so I’ve heard, from a friend of a friend 😉 ) ---
**Author:** ![Beagle](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Beagle](https://boards.straightdope.com/u/Beagle)\ **Post date:** [June 29, 2003, 3:22pm UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/10 "2003-06-29T15:22:16Z")
> [@](#): > > \*Originally posted by Marley23 \* > \*\*The study doesn’t say weed isn’t harmful, it says it doesn’t cause a lot of long-term brain damage. \*\* Bob, is that you? Sorry about the brain tumor… You’re right, in that the study was on brain function and not the lungs. [OTOH, what about all this stuff?](http://www.theantidrug.com/marijuana/index.html) > [@](#): > > Effects of Marijuana on the Brain. Researchers have found that THC changes the way in which sensory information gets into and is acted on by the hippocampus. This is a component of the brain’s limbic system that is crucial for learning, memory, and the integration of sensory experiences with emotions and motivations. Investigations have shown that THC suppresses neurons in the information-processing system of the hippocampus. In addition, researchers have discovered that learned behaviors, which depend on the hippocampus, also deteriorate. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 29, 2003, 3:48pm UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/11 "2003-06-29T15:48:09Z")
> [@](#): > > \*Originally posted by Beagle \* > \*\*[OTOH, what about all this stuff?](http://www.theantidrug.com/marijuana/index.html) \*\* It looks like the study in the OP is talking about long term effects while your link seems to indicate immediate effects. I don’t think anyone is suggesting that marijuana doesn’t in some way impair you while using it. ---
**Author:** ![CarnalK](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnalk/32/486_2.png) [@CarnalK](https://boards.straightdope.com/u/CarnalK)\ **Post date:** [June 29, 2003, 4:34pm UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/12 "2003-06-29T16:34:24Z")
> [@](#): > > Investigations have shown that THC suppresses neurons in the information-processing system of the hippocampus. In addition, researchers have discovered that learned behaviors, which depend on the hippocampus, also deteriorate Hmm, so researchers have found that being high might affect your brain. Interesting stuff. 🙂 ---
**Author:** ![Beagle](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Beagle](https://boards.straightdope.com/u/Beagle)\ **Post date:** [June 29, 2003, 4:46pm UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/13 "2003-06-29T16:46:40Z")
Good point. “Change” does not equal long-term. I don’t think the quote is particularly clear. That’s my story, and I’m sticking with it. ---
**Author:** ![Verminous](https://avatars.discourse-cdn.com/v4/letter/v/5e9695/32.png) [@Verminous](https://boards.straightdope.com/u/Verminous)\ **Post date:** [June 30, 2003, 1:45am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/14 "2003-06-30T01:45:52Z")
Thing is, they’re basically comparing the brains of users vs. non-users. There’s a host of problems in doing it that plainly. What if the non-users are simply better learners and have better memories? The users simply being slower to begin with? A better study would be to test people pre-marijuana use, then post-marijuana use. This of course has been done before, I’m sure…I’ll need to google that query… ---
**Author:** ![CarnalK](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnalk/32/486_2.png) [@CarnalK](https://boards.straightdope.com/u/CarnalK)\ **Post date:** [June 30, 2003, 2:49am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/15 "2003-06-30T02:49:49Z")
**Verminous** -_A better study would be to test people pre-marijuana use, then post-marijuana use. This of course has been done before, I’m sure…I’ll need to google that query…_ Well you could start by looking at the CMAJ article I linked above. It began with kids ages 9-12, before any marijuana use. ---
**Author:** ![MmmDonut](https://avatars.discourse-cdn.com/v4/letter/m/d6d6ee/32.png) [@MmmDonut](https://boards.straightdope.com/u/MmmDonut)\ **Post date:** [June 30, 2003, 4:41am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/16 "2003-06-30T04:41:06Z")
Well, considering I’ve read the previous studies, the vast majority of which concluded that marijuana is essentially harmless to long-term cognitive functioning, this does not surprise me in the least. However, I did not need science to tell me this. I know plenty of older smokers who, on average, tend to be remarkably intelligent and insightful people. I know college students who smoke it on a daily basis, and in large quantities, yet still have perfect grades, a healthy social life, and all the stuff that goes with being a “normal” contributing member of society. Now, someone tell me, why is it illegal? If anything, its use should be encouraged as a substitute for alcohol, a drug that WILL destroy healthy lives if used daily. It’s a shame; most people like to “get high”, in one form or another. If we can accept that as an innate desire all humans possess, the least we should do is find things that we can consume safely. Why shouldn’t it be marijuana? ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [June 30, 2003, 4:43am UTC](https://boards.straightdope.com/t/new-ucsd-study-on-marujuana-not-harmful/185115/17 "2003-06-30T04:43:25Z")
> [@](#): > > You’re right, in that the study was on brain function and not the lungs. Yes. I wouldn’t argue your comment about government pressure, and we’ve been fed a lot of crap about drugs over the years. What I was disagreeing with is in the thread title - “marijuana: not harmful?” It IS harmful in some ways, even if we’re finding it doesn’t cause a lot of long-term impairment in brain function.