Does pot really lower IQ? It's not so simple

By Tia Ghose, LiveScience 

Marijuana permanently lowers IQ by several points in adolescents, according to research published in August. But a new study suggests that factors related to economic class and home life, not marijuana use, may have caused that IQ drop.

Researchers who conducted the new study, published today (Jan. 14) in the journal Proceedings of the National Academy of Sciences, did not have access to the original data from a cohort of New Zealand teenagers. Instead, Ole Rogeberg, a labor economist at the Frisch Center in Norway, used a computer simulation to show that, in theory, the same IQ effects could be explained by socioeconomic factors that cause IQ-decreasing behaviors.

The new results are sure to ignite a firestorm of debate over whether marijuana permanently harms the growing brain.

"The kinds of environments you are in do affect your IQ," Rogeberg said. Good education and challenging jobs can boost intelligence, but "if people are pushed out or decide to move out of these kinds of arenas, they will tend to see an IQ decline, and they will also be the type of people who tend to take up cannabis smoking during adolescence."

The original study can't rule out the possibility that other factors could play a role in the link between IQ and marijuana usage, said Susan Tapert, a neuropsychologist at the University of California, San Diego, who was not involved in the study, in an email.

"This was an excellent study – large, and followed the same individuals over time.  Even still, the possibility of some other unmeasured issue to drive this link remains," Tapert wrote.

The initial study, by researchers Madeline Meier, Terrie Moffitt and Avshalom Caspi of Duke University, relied on an unprecedented amount of data from a cohort of 1,037 people from Dunedin, New Zealand, who have been followed for more than three decades. The exhaustive study tracked people from age 7 onward, subjecting them to IQ tests, collecting blood samples, and interviewing parents and teachers at several points along the way.

The team found that marijuana lowered IQ by as much as eight points for heavy, lifelong users who started in adolescence. Marijuana use had no effect if people picked up the habit as adults, suggesting that marijuana was especially harmful for developing brains. [ Adolescent Angst: 10 Facts About the Teen Brain ]

But socioeconomic class and family structure can change IQ over time. For instance, poorer children tend to choose less challenging schools or work, even if they start out with the same IQ as higher-income kids. Economic class may also affect the development of traits like motivation and perseverance that could affect later-life IQ.

Rogeberg created a mathematical model to see if the apparent effect of marijuana on IQ could be explained by socioeconomic factors.

He found they could.

That doesn't mean marijuana is harmless, Rogeberg told LiveScience. Instead, the original researchers should do a more thorough analysis to prove that marijuana, and not other aspects of the pot-smoking lifestyle, cause lower IQ, he said.

That should include testing to see whether cannabis use altered individual people's IQ trajectories from age 7 onward. Research should also look at the cumulative impact of various factors, such as home life or education level, that may negatively impact IQ, to see if this cumulative effect could explain the drop seemingly caused by pot smoking.

"It might be the totality of factors could explain a large part of the effect that they found," Rogeberg said.

In response, the authors of the past scientific paper conducted a new analysis and found that IQ overall remained fairly stable in the Dunedin participants, they said in a statement. They also only included kids from middle-class families, eliminating the effects of socioeconomic status, they said.

But Rogeberg says those steps can't rule out other factors as the cause for lower IQ.

"While interesting, the new analysis is not at all sufficient to address these concerns – but I look forward to seeing a fuller analysis in time," Rogeberg said.

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Bugsy-3651441

Pot won't lower your IQ as long as you don't inhale. Just ask Bill Clinton, Rhodes Scholar.

Ah good 'ol slick Willy. I heard Monica just turned 44, oh my God how time flies. It seems like just last week she was crawling around the oval office floor putting things in her mouth.

  • 5 votes
Reply#27 - Mon Jan 14, 2013 5:31 PM EST

I liked that! Lol!

    #27.1 - Mon Jan 14, 2013 5:34 PM EST
    Comment author avatarZebulon Hazevia Facebook

    Good one !!

      #27.2 - Mon Jan 14, 2013 7:16 PM EST

      Don't forget where Uncle Bill shoved the cigar!

      • 1 vote
      #27.3 - Mon Jan 14, 2013 7:39 PM EST
      Reply

      Someone break out the Cheetos and extra cheese pizza....

        Reply#28 - Mon Jan 14, 2013 5:33 PM EST

        Does it inhibit motivation? Images of my old unemployed roommate staring at a broken TV for 3 hours and stealing my food in the middle of the night to avoid walking 100 feet to the store indicates a pretty stong correlation.

        • 1 vote
        Reply#29 - Mon Jan 14, 2013 5:35 PM EST

        Pot had nothing do with it. You just had a lazy room mate!

        • 5 votes
        #29.1 - Mon Jan 14, 2013 5:41 PM EST

        I'm sitting here alone

        in front of the TV

        i't not even on but

        there is plenty for me to see

        I just lit some crazy ass sh1t

        that me friend overnight mailed to me

        You know the rest.

          #29.2 - Mon Jan 14, 2013 5:41 PM EST

          Smeado, Your room mate was a BUM.

          Bums come in all shapes and sizes. Some bums don't need drugs or alcohol. They just need a sucker to suck off of. D'oh!

          • 4 votes
          #29.3 - Mon Jan 14, 2013 7:44 PM EST
          Reply

          If you don't believe POT smoking lowers your IQ, and you require some form of life saving surgery, then by all means select a stoner for a Surgeon, or if you are taking a flight then try the stoner airlines. Just as I thought, no takes!!!

          • 1 vote
          Reply#30 - Mon Jan 14, 2013 5:36 PM EST

          Yeah right....I'd rather they were juicers. I'll take a stoned surgeon before a drunk one if those were my only choices. Your argument is ridiculous. I don't want either to be using alcohol or marijuana. I've smoked for 40 years but never at work. Do you drink at work!

          • 5 votes
          #30.1 - Mon Jan 14, 2013 5:39 PM EST

          Well lets see. Quite a few anesthesiologists are addicted to opiates from exposure during surgeries, yeah I'll take someone under the influence of MJ. And pilots? Yeah I'll take a stoned one over a drunk one any day.

          • 3 votes
          #30.2 - Mon Jan 14, 2013 6:27 PM EST

          Minnsurveyor, have you ever misplaced your keys on your high days? Just wondering since your seem to ask me if I drink at work. You must work for an employer that doesn't require mandatory drug testing, or you work for yourself. Probably better that you don't fly a Commercial Airline or perform Surgery. 40 years of smoking, how old were you when you started, 10?

          • 1 vote
          #30.3 - Mon Jan 14, 2013 6:33 PM EST

          And pilots? Yeah I'll take a stoned one over a drunk one any day.

          Know any that are still flying? Most are drinkers that I have known, but according to FAA rules, they cannot drink within a certain time-frame of flying, and YES drug testing is mandatory. Get caught flying while high on weed and you are gone from the profession? Back to flying gliders in the dessert with the rest of the hippies!

          • 1 vote
          #30.4 - Mon Jan 14, 2013 6:36 PM EST

          Spo de de de,

          Are you naive or ignorant? Because you sure don't have a clue about the real world. Myself, I have a high level security clearence and if I get caught smoking weed I could lose my job. But since I've been with the company for 30 years and since they have invested millions in me. They would offer me drug rehab before they fire me (It says so in our manual).... A 100 drug tests later, clean every time ........ Oops... I've been smoking weed since 1973.

          • 4 votes
          #30.5 - Mon Jan 14, 2013 7:56 PM EST

          Steamie, definitely sounds like you have a self-promoting position, or so you say, with the current administration or as a government contractor. In the Real World of Private Industry, no matter how important you may think you are, you get fired when caught, which is how it should be in the Government. Keep smoking those blunts, you never know when big brother is watching.

          • 1 vote
          #30.6 - Mon Jan 14, 2013 9:41 PM EST

          Quite a few anesthesiologists are addicted to opiates from exposure during surgeries

          BS. If an anesthesiologist has become addicted to opiates it is because that anesthesiologist has been consuming opiates, not from exposure during someone else's surgery.

          • 2 votes
          #30.7 - Mon Jan 14, 2013 10:59 PM EST

          Steamie, definitely sounds like you have a self-promoting position, or so you say, with the current administration or as a government contractor. In the Real World of Private Industry, no matter how important you may think you are, you get fired when caught, which is how it should be in the Government. Keep smoking those blunts, you never know when big brother is watching.

          Well, Spodeo, sounds like you most likely have a no promotion, factory line job. Most companies have a peer assistance program that would cover their valued employees that are not so easily replaced.

          • 2 votes
          #30.8 - Mon Jan 14, 2013 11:03 PM EST

          Well, Spodeo, sounds like you most likely have a no promotion, factory line job.

          DOCJT, not even close. Most private companies have a zero tolerance policy like the government should. Sounds like you have a Union mindset!

          • 1 vote
          #30.9 - Tue Jan 15, 2013 11:33 AM EST

          Spo de o de, Minnsurveyor stated that he was 60 years old and has smoked for 40 years. You should brush up on your math or try smoking some weed.

            #30.10 - Fri Apr 26, 2013 4:13 PM EDT
            Reply

            A difference of 8 IQ points is about as trivial as this offering from the world of publish or perish academia. I know they have to publish something to justify their paychecks and enhance (?) their academic standing but one would think they could do better than this.

              Reply#31 - Mon Jan 14, 2013 5:47 PM EST

              Ridiculous. Alcohol destroys brain cells. Fact. I started smoking pot at 15 (in 1969), I had a 4.0 GPA in college and ended up in a great job. I own my house and have many hobbies and friends and yes, at 58, I still occasionally take a toke.

              Ricardoh-you sound like an uninformed douchebag.

              • 7 votes
              Reply#32 - Mon Jan 14, 2013 5:47 PM EST

              I'm around the same age, and I also graduated from college with honors (Information Systems). I didn't quit until after I graduated.

              • 2 votes
              #32.1 - Mon Jan 14, 2013 5:50 PM EST
              Reply

              Pot smokers are just plain stupid. No need to do a comparison or analysis. The fact that the majority voted to make pot legal goes to show how many stupid people are in this country. All of our technical and professional jobs are being filled by foreigners because people here are to lazy or stoned to learn anything.

              • 1 vote
              Reply#33 - Mon Jan 14, 2013 5:54 PM EST

              By the fact of your comment I can see what a terrible dad you are and how you don't listen to anybody but yourself and what you have obviously already made up your mind about. If more parents listened to their kids and tried to find out why kids got into drugs instead of condemning them, this world would be a better place. You think you know it all but your kids probably wish you were not their dad, and those kids are exactly the type of kids who turn into addicts because they are so messed up.

              • 4 votes
              #33.1 - Mon Jan 14, 2013 6:11 PM EST

              Your babble is not prolific. You're an idiot. STFU! My kids are grown up now and they don't do drugs.

              • 1 vote
              #33.2 - Mon Jan 14, 2013 6:21 PM EST

              DadInAZ-3698986

              Pot smokers are just plain stupid. No need to do a comparison or analysis.

              OK everyone, some dude in AZ said we don't need a comparison or analysis, we can go on with our lives now.

              The fact that the majority voted to make pot legal goes to show how many stupid people are in this country

              Everyone but you, am I right?

              All of our technical and professional jobs are being filled by foreigners because people here are to lazy or stoned to learn anything.

              Wow, I'm so glad you have the answer to what the problems our country is facing, laziness and reefer madness. Why don't you go ahead and join us in the 21st century?

              • 3 votes
              #33.3 - Mon Jan 14, 2013 6:35 PM EST

              You're a pot smoker right? Yeah I thought so...........

                #33.4 - Mon Jan 14, 2013 6:53 PM EST

                Your babble is not prolific.

                If you want to attempt to sound intelligent by using a 'big' word, you might want to use one that's actually appropriate. I can assure you that any child of yours would be highly (no pun intended) inclined to do drugs. Since you seem to have all the answers, let me ask you this: What percentage of 'dads' are aware that their kids smoke pot? Yeah, I thought so...

                • 3 votes
                #33.5 - Mon Jan 14, 2013 7:17 PM EST

                Your babble is not prolific. You're an idiot. STFU! My kids are grown up now and they don't do drugs.

                LOL yep, your kids are perfect little angels and have never gone binge drinking or smoked pot LOL You're the best parent in the world!!!!

                • 3 votes
                #33.6 - Mon Jan 14, 2013 7:42 PM EST

                Thank you. I know more about my kids that you do. Jealous or just plain stupid? Probably both. You all show the maturity of a 3 year old. Impressive.

                  #33.7 - Mon Jan 14, 2013 7:56 PM EST

                  I'm sure you know less than you think you know.

                  And I don't have kids... so nothing to really be jealous about.

                  • 2 votes
                  #33.8 - Mon Jan 14, 2013 8:11 PM EST

                  Dad the Out Of Touch Dip Stick,

                  What? Only americans do drugs? What A Major Ignorant Statement!

                  I guess you've never been over seas? Every single country in the world has drug & alcohol problem!

                  Plus if you do have kids. You sound like the kind of prick that the kids would hide and lie about drug use around you. Because your little Bull Sh!t bubble would pop and you would explode like a mean drunk! What an idiot!

                  • 4 votes
                  #33.9 - Mon Jan 14, 2013 8:20 PM EST

                  My kids are grown up now and they don't do drugs.

                  That you are aware of. I'd venture to say your kids probably do a lot of stuff they don't tell you about, given your judgemental and intolerant presentation of yourself.

                  • 5 votes
                  #33.10 - Mon Jan 14, 2013 11:06 PM EST

                  You've been convinced by the daddy feds that pot is oh so terrible, yet you have't seen anybody go out on shooting sprees killing kids, and people guess what every one of those shootings the person was on a prescribed drug. Hmmm who douses those out , Hmmm depression, the drs. Pot doesn't do jack or s--- to you no where near as bad as this prescription drugs. Hell they even tell you on the inside packet it might kill you, I bet you pop 5 prescribed drugs a day cause the trusty Dr said so, and the trusty Dr says it's ok, and little do you realize how rich you are making the big pharmas, and you wittle Dr. gets kickbacks for followin bid daddy feds little policey, wait til your Dr ask you if you have a gun PER DADDY OBAMANUS... is that ok to cause he says so.

                  U.S. Government owns the patent on cannabis cures...

                  2003 is when they got it too.

                  The NMDA receptor is one of two kinds of receptors activated by glutimates).

                  This new found property makes cannabinoids useful in the treatment and prophylaxis of a wide variety of oxidation associated diseases, such as ischemic, age-related, inflammatory and auto-immune diseases. The cannabinoids are found to have particular application as neuroprotectants, for example in limiting neurological damage following ischemic insults, such as stroke and trauma, or in the treatment of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and HIV dementia.

                  Nonpsychoactive cannabinoids, such as cannabidoil (mis-spelled in document - should read cannabidiol), are particularly advantageous to use because they avoid toxicity that is encountered with psychoactive cannabinoids at high doses useful in the method of the present invention. A particular disclosed class of cannbinoids useful as neuroprotective antioxidants is formula (1) wherein the R group is independently selected from the group consisting of H, CH.sub3, and COCH.sub3. ##STR1##

                  In other words, THE GOVERNMENT ALREADY OWNS THE ORGANIC THC OIL BY FORCE... and now THEY OWN THE SYNTHETIC THC OIL BY PATENT... along with any and all combinations of the beneficial compounds found in cannabinoids. As you read through this document you will discover beyond any doubt whatsoever that cannabis has a tremendous variety of medicinal values and applications specific and provable enough to be granted a U.S. Patent, yet the Judicial Branch of our government continues to classify cannabis as a Schedule 1 Controlled Substance

                  you can find that info on the daily Paul dot the com

                  • 1 vote
                  #33.11 - Fri Jan 18, 2013 3:20 PM EST
                  Reply

                  8 points on an iq test is not something to be concerned with unless your iq is 132 and you wanted to be labeled a genius. (140 or higher)

                  in the matter of trivia for trivia's sake, if your iq was 138 when you were in the 7th grade then what should it be when you are an old fart and no longer need it.

                  • 1 vote
                  Reply#34 - Mon Jan 14, 2013 5:54 PM EST

                  I spent 2 years in the 7th grade. In a Mensa test my score was 139.That was last year when I was 76. I'll try again this year to see if I have become smarter.

                    #34.1 - Mon Jan 14, 2013 6:10 PM EST
                    Reply

                    Aside from all the jokes, there really is a serious side to this. Some people (especially teenagers) have brains that are too active. Their minds are running at a very high state of attention, and they have little control of it. This leads to symptoms like neurosis, depression and obsession.

                    For some youth, this leads to very risky behaviors. In my childhood I had several friends who "huffed" glue, cleaning fluids or even gasoline. I could never get them to tell my why they did it. I tried it and it just made me very sick to my stomach. Sadly, all these friends all have long since died.

                    On the other hand, the kids who smoked marijuana survived, and most ended up in creative careers, like art, writing or music. I myself ended up as a programmer in computing systems and even worked as a hospital technician for a few years.

                    I think that serious scientists need to do serious studies. really, we can observe our own little corner of the world and assume its the same for everyone, everywhere. But it is not. Good science will probably lead to better outcomes than passing laws based on intolerance and prejudice.

                    A wise society will get all the facts before passing laws. Lack of a non-lethal intoxicant does, in my opinion, lead to use of destructive substances. The real question is how do those statistics bear out when applied to millions of lives, in diverse conditions?

                    • 1 vote
                    Reply#35 - Mon Jan 14, 2013 5:56 PM EST

                    A previous study stated heavy users had their IQs lowered by a somewhat statistically insignificant number, another researcher went back through the data and discovered it shpwed casual use actually increased IQ. Man did that study disappear fast, now we have another one, but note it states adolescents. I don't see many people advocating young adolescent using any drug, except for big pharama of course, but I know a lot of politicians who think we should lower the drinking age, imagine that.

                    • 4 votes
                    Reply#36 - Mon Jan 14, 2013 5:56 PM EST

                    A lot of the people commenting on this topic haven't used marijuana so they don't really know what they are talking about. I personally don't believe it kills brain cells, but it seems to take away the drive to attain money and power over others. If you want to keep your kids from experimenting with drugs, the most important thing I would say would be to give them the feeling that you care about them, to listen to them and to talk to them a lot and really listen to what they are saying. I really think to this day the reason I spent so much time in my youth smoking pot and doing drugs is because I had very low self worth, I felt that nobody paid any attention to me or cared about me in any way. No matter how smart you are, if you feel no one cares about you, you are gong to seek ways to dull the pain of that. You can't buy off your kids with gifts or money, you have to put in the time with them. If you would rather not spend that time with your family and then your kids turn to drugs later, don't pretend that it is some bad influence outside the home that caused it. It is your own fault. Nobody twisted your arm and made you buy a five bedroom home with a three car garage. That is not what kids need. They need someone who eats dinner with them every night and really wants to know how their day went, and someone who shows up at their athletic events to cheer them on. The kids that can't count on their folks to support them emotionally are the ones who fall off the cliff and turn to drugs because they hurt, not because they're bad.

                    • 1 vote
                    Reply#37 - Mon Jan 14, 2013 5:59 PM EST

                    IQs are pretty low to start with. The decisiont to smoke pot makes your IQ even lower.

                      Reply#38 - Mon Jan 14, 2013 6:02 PM EST

                      IQ doesn't change much over the course of a person's lifetime, regardless. The figure I've seen most often is +/- 10%, due to age and a number of other factors. If your doing drugs or alcohol, then naturally it's going to have an adverse affect on your cognitive functioning, both while you're high and long-term even when you're in a normal state. No great revelation there.

                      I don't really think it takes a university-sponsored study to tell most people that their children should not be smoking pot while they're in the formative years and going to school high. I'd like to see the research money spent on something more practical, like whether GMO crops are dangerous for us to be consuming.

                      • 2 votes
                      Reply#39 - Mon Jan 14, 2013 6:03 PM EST

                      A little research into MONSANTO, a darling of the US Judicial system, will confirm that they are...........

                      • 1 vote
                      #39.1 - Mon Jan 14, 2013 6:21 PM EST
                      Reply

                      From my personal experience, and after smoking pot almost daily for the last 35 years ( since i was 14 ), I'd say that the effect on IQ is minimal. My IQ score hasn't changed all that much since I was 10. For reference, I still scored 135 on the last IQ test I took about a year ago.

                      • 1 vote
                      Reply#40 - Mon Jan 14, 2013 6:05 PM EST

                      What about alcohol? How does that affect adolescent brains? This is ridiculous study.

                      • 2 votes
                      Reply#41 - Mon Jan 14, 2013 6:07 PM EST

                      As are all 'corporation' funded studies done in USA Universities.

                      • 1 vote
                      #41.1 - Mon Jan 14, 2013 6:20 PM EST
                      Reply

                      It depends on the Pot. Different strains of cannabis will affect you in different ways. Some strains promote creativity, some promote wonderment, some make you happy, some make you goofy, some make you introspective, some make you think a lot, some make you paranoid and some make you lazy. If you have a low IQ to start with, it'll probably just make you stoned...

                      • 2 votes
                      Reply#42 - Mon Jan 14, 2013 6:08 PM EST

                      Couch lock forever!

                        #42.1 - Mon Jan 14, 2013 6:24 PM EST
                        Reply

                        Speaking from personal experience: I had a horrible home life growing up, and I was an avid pot smoker. My IQ has been tested at 142... so I'd have to say that it really depends upon the person as to whether or not these factors play a part in their IQ.

                        • 2 votes
                        Reply#43 - Mon Jan 14, 2013 6:09 PM EST

                        What do Americans need with a high IQ? It just makes the job of bull*hitting us more difficult for TPTB. Plus, the majority of jobs have been off shored..

                        Just saying,

                        A proud 47% er.

                        • 1 vote
                        Reply#44 - Mon Jan 14, 2013 6:14 PM EST

                        Marijuana lowers your IQ like "fast food" causes asthma and allergies: it doesn't.

                        Correlation is not causality, and Journalism is not science.

                        Journalists? Does you mother know what you do for a living? Does she know you are peddling sensationalist garbage on a daily basis. You should be ashamed!

                        • 1 vote
                        Reply#45 - Mon Jan 14, 2013 6:15 PM EST

                        Wait let me pass this over to my friend so I can type!!

                        Where do I sign up to take part in this study???

                          Reply#46 - Mon Jan 14, 2013 6:18 PM EST

                          In the USA, CORPORATIONS fund these colleges for 'research' that gives them the purchased results they want. Sounds like these Duke 'academics' just ripped of Big Pharma and the Booze industry, both of which are famous for killing their 'clients.' Ha ha!

                            Reply#47 - Mon Jan 14, 2013 6:18 PM EST

                            They should be asking " DO VACCINES LOWER YOUR IQ" I wouldn't trust a dam thing coming from the Feds and their studies. I wouldn't even trust the FDA and their bs stories. Hemp oil has been known to cure so many things it's sickening and the feds keep that ifnormation from the public. Dont believe it look up how the sob's just put a patent on it in 2003.

                            U.S. Government owns the patent on cannabis cures...

                            • 2 votes
                            Reply#48 - Mon Jan 14, 2013 6:20 PM EST

                            This is no real surprises. Look at all the "flower" children of my generation. There all potheads. Most are democrats.

                            • 1 vote
                            Reply#49 - Mon Jan 14, 2013 6:21 PM EST

                            Then it does raise IQs!

                            • 7 votes
                            #49.1 - Mon Jan 14, 2013 6:30 PM EST

                            This is no real surprises. Look at all the "flower" children of my generation. There all potheads. Most are democrats.

                            I bet they know the difference between "there" and "they're", too. And how to make verb and subject in a sentence agree. Just sayin'.

                            • 2 votes
                            #49.2 - Mon Jan 14, 2013 11:13 PM EST
                            Reply

                            I was warned about the dangers of pot but can't remember any of them.

                            • 1 vote
                            Reply#50 - Mon Jan 14, 2013 6:23 PM EST

                            lmao hal

                            • 1 vote
                            #50.1 - Mon Jan 14, 2013 6:24 PM EST

                            A lot of cats don't think pot should be legalized because they say things like it affects your memory. I just want to say... I forgot what I was going to say man.

                              #50.2 - Mon Jan 14, 2013 6:32 PM EST
                              Reply

                              This type usually has a drink in one hand while they lecture against the evils of marijuana. Amazing the number of alcoholics and prescription drug addicts who are against smoking weed...........

                              • 3 votes
                              Reply#51 - Mon Jan 14, 2013 6:26 PM EST
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