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Twins Study Finds No Evidence That Marijuana Lowers IQ In Teens (sciencemag.org)

sciencehabit writes: Roughly half of Americans use marijuana at some point in their lives, and many start as teenagers. Although some studies suggest the drug could harm the maturing adolescent brain, the true risk is controversial. Now, in the first study of its kind (abstract), scientists have analyzed long-term marijuana use in teens, comparing IQ changes in twin siblings who either used or abstained from marijuana for 10 years. After taking environmental factors into account, the scientists found no measurable link between marijuana use and lower IQ.

15 of 307 comments (clear)

  1. Re:Great Parents!! by Anonymous Coward · · Score: 3, Insightful

    You don't have much experience thinking about medical issues, I take it?

  2. Re:It's not just about IQ by Anonymous Coward · · Score: 1, Insightful

    How did they measure motivation, or paranoia,

    Stoners become stoners because of lack of motivation, not the other way around. They're paranoid because they engage in an illegal lifestyle and the law is literally out to get them.

  3. Re:Great Parents!! by Anonymous Coward · · Score: 2, Insightful

    Science cares about reality.

    Your fiction of "what if" and fear of the unknown is how we ended up with prohibition in the first place. This attitude that "if it feels good it must be bad for you" is puritan, religious non-sense.

    Marijuana is common place is society, and scientifically it has been shown to be rather benign.

  4. Re:Great Parents!! by Anonymous Coward · · Score: 0, Insightful

    You posted an comment so vague it is meaningless. You did not provide anything agreeing with or refuting what was written.

  5. Re:Great Parents!! by ArmoredDragon · · Score: 4, Insightful

    It was likely survey based. I.e. they found identical twins and asked them if one used and one didn't, and if so, they evaluated them afterwards.

    Anyways I'm kind of disappointed that they only looked at IQ, as to me it's a meaningless figure whose only purpose is for "I am more smug than thou art" clubs like Mensa. I'm more curious about other functional measurements both physiologically and sociologically (i.e. how did they vary in terms of career success.) There's some evidence that marijuana can improve both, as well as evidence that it can harm both.

  6. Is there a false assumption here? by frovingslosh · · Score: 2, Insightful

    There seems to be an implication here that twins have identical IQs. I don't think that is valid and it strike me as more likely that the twin with the lower IQ is the one who elects to abstain from wacky weed and the twin with the higher IQ is burning out brain cells until they get down to their sibling's level.

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    I'm an American. I love this country and the freedoms that we used to have.
  7. Re:It's not just about IQ by NatasRevol · · Score: 5, Insightful

    Very smart people are not always very motivated people. And vice versa.

    Take politics as an example.

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    There are two types of people in the world: Those who crave closure
  8. Re:who cares? by mark-t · · Score: 1, Insightful

    It's a million times safer than alcohol.

    When looking at the big picture, and taking its overall negative impact on a person's health over a person's entire lifetime, quite possibly.... in terms of the immediate effects on one's motor skills, not so much.

  9. Re:Great Parents!! by Firethorn · · Score: 4, Insightful

    And if drugs policy is to be based on facts then this sort of fact is just one more reason to give it up already and let adults decide what plants they'd like to benefit from.

    Indeed. There is a real problem when the biggest detriment that people can identify for using an illegal drug is the very fact that it's illlegal. When the primary concern isn't that the drug will kill you, put you in the hospital, give you organ damage, make you crazy, or make you dependent upon it, but is instead that you'll be fined or tossed into jail, something has gone horribly wrong.

    When you have people taking 'bath salts' instead of cocaine, which has a much higher chance of, I don't know, chewing somebody's face off, because the latter is illegal as well as the former, but the 'bath salts' are more accessable for those that would use drugs, we have a problem.

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    I don't read AC A human right
  10. Re:Great Parents!! by swb · · Score: 4, Insightful

    The "safety" argument relative to drug legalization is huge red herring designed to drag legalization proponents down the path of needing to claim that marijuana is safer than tap water, or worse, into wild and unproven claims of its medical benefits.

    The results of marijuana's relative safety have been in for years -- you can't really overdose on it and decades of mass use have failed to show any significant signs of problems in the general population. This is more than we can say about alcohol, acetaminophen, anti-depressants and whole long laundry list of substances that are legal and easy to get.

    The REAL argument is that the public policy of marijuana criminalization has been an abject failure. We've spent trillions of dollars on prohibition on it and all we have to show for it is a complete dismantling of our constitutional rights, corruption of a law enforcement system that has produced an epidemic of civil rights abuses quite often enabled by the elusive pursuit of marijuana users (you didn't think they wanted to stop you for a traffic offense, did you?), an erosion in public respect for laws, almost certainly a disregard for the graver risks posed by other illegal drugs, and a criminal justice system that has ruined thousands of lives and built massive criminal enterprises

    What we don't have to show for it is any reduction in marijuana use or availability. As a matter of public policy it has failed in its goals and produced a plague of horrific side effects.

    This is the argument that needs to be made. The safety issue is a total and complete distraction.

  11. Re:It's not just about IQ by Anonymous Coward · · Score: 5, Insightful

    No, most of us aren't familiar with your anecdotes.

  12. Re:It's not just about IQ by Anonymous Coward · · Score: 2, Insightful

    I've seen plenty of people who don't smoke weed become listless lumps, especially teens and young adults. I've also seen plenty of stoners become excellent writers, artists, and musicians, as well as teachers, programmers, etc..

  13. Re:Great Parents!! by Cute+Fuzzy+Bunny · · Score: 3, Insightful

    I think the big problem here is reliance on any test intended to show off levels of intelligence. Many of the cheaper, simpler to administer tests vary wildly in both consistency and accuracy.

    Most US schools rely on a specific test to determine gifted/intelligence level. Its cheap and easy to do and doesn't take long. Its primary problem is that in the case of very gifted kids, the test results reverse themselves and may even indicate that a very introverted, very intelligent kid is well below average in intelligence. Then you give the same kid that same test a month later when they're focused and interested in the test and you get a completely different result.

    So if you want to show in a study that average scores are lower, use the cheap test. If you want to show higher average scores, use the expensive long tests that capture all of the kids with IQ's over 125 instead of showing them at 80-90.

    As far as the original story, I was a regular 'user' in my 20's and dabbled with it infrequently for 30 years. I don't think it reduced my intelligence but it sure does cut into motivation and aggression. One interesting metric I've seen was getting my social security statement a few years ago which showed my annual income since I was a teen. It goes up smoothly and sharply until about the time I started smoking pot. Then it flies level for about five years until I gave it up at which point the income numbers resume the same sharp upward line.

    It'd seem to me that the last thing a teenager needs is less motivation and less interest in doing things.

  14. Re:Great Parents!! by PopeRatzo · · Score: 4, Insightful

    Cannabidiol (CBD) and tetrahydrocannabinol (THC) are different thngs. THC is psychoactive, CBD is not.

    It's a sad comment on our society where we are so worried that there might be some natural substance that makes people feel good that before an effective drug can be approved the feel-good properties have to be removed.

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    You are welcome on my lawn.
  15. Re:Great Parents!! by Qzukk · · Score: 3, Insightful

    It's the same society that flipped it's shit when someone invented a vaccine against a virus that causes cancer, for much the same reasons.

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    If I have been able to see further than others, it is because I bought a pair of binoculars.