Marijuana and Schizophrenia

January 11th, 2011 at 8:06 am David Frum | 55 Comments |

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My weekend blogpost noting the link between schizophrenia and heavy marijuana smoking evoked a certain (ie large) amount of derision. The libertarian spirit of the Internet does not like to hear bad news about prohibited drugs.

But the evidence that marijuana can trigger psychosis among those genetically predisposed to schizophrenia is strong. This site does a good round up of the (disturbing) literature:

sales helvetica, pilule geneva,lucida sans,sans-serif;”>Most Recent Scientific Research on Schizophrenia and Cannabis:

Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases. Br J Psychiatry. 2005 Dec;187:510-5

Toward a world consensus on prevention of schizophrenia.
Dialogues Clin Neurosci. 2005;7(1):53-67.

Risk for schizophrenia–broadening the concepts, pushing back the boundaries.
Schizophr Res. 2005 Nov 1;79(1):5-13.

The environment and schizophrenia: the role of cannabis use.
Schizophr Bull. 2005 Jul;31(3):608-12. Epub 2005 Jun 23.

Predictors of schizophrenia–a review.
Br Med Bull. 2005 Jun 9;73:1-15. Print 2005.

Cannabis as a risk factor for psychosis: systematic review.
J Psychopharmacol. 2005 Mar;19(2):187-94.

Cannabis use prior to first onset psychosis predicts spared neurocognition at 10-year follow-up.
Schizophr Res. 2005 Jun 1;75(1):135-7.

[Acute and chronic cognitive disorders caused by cannabis use]
Rev Prat. 2005 Jan 15;55(1):23-6; discussion 27-9. French.

Delta-9-tetrahydrocannabinol effects in schizophrenia: implications for cognition, psychosis, and addiction.
Biol Psychiatry. 2005 Mar 15;57(6):594-608.

Cannabis use and psychotic disorders: an update.
Drug Alcohol Rev. 2004 Dec;23(4):433-43. Review.

Is cannabis an anti-antipsychotic? The experience in psychiatric intensive care.
Hum Psychopharmacol. 2005 Apr;20(3):207-10.

Cannabis and risk of psychosis.
Swiss Med Wkly. 2004 Nov 13;134(45-46):659-63. Review.

[Cannabis can double the risk of schizophrenia. Increasing but still controversial knowledge of the psychological effects of the drug]
Lakartidningen. 2004 Oct 7;101(41):3126-7. Swedish.

Is the party over? Cannabis and juvenile psychiatric disorder: the past 10 years.
J Am Acad Child Adolesc Psychiatry. 2004 Oct;43(10):1194-205. Review.

Adverse effects of cannabis on health: an update of the literature since 1996.
Prog Neuropsychopharmacol Biol Psychiatry. 2004 Aug;28(5):849-63. Review.

Cannabis use and risk of psychosis: an etiological link?
Epidemiol Psichiatr Soc. 2004 Apr-Jun;13(2):113-9. Review.

[Cannabis and schizophrenia. From euphoria to psychosis]
Rev Med Liege. 2004 Feb;59(2):98-103. French.

Heavy cannabis users seeking treatment- prevalence of psychiatric disorders.
Soc Psychiatry Psychiatr Epidemiol. 2004 Feb;39(2):97-105.

Cannabis use and the risk of later schizophrenia: a review.
Addiction. 2004 Apr;99(4):425-30. Review.

Cannabis use and psychosis.Drug Alcohol Rev. 1998 Dec;17(4):433-44.

Cannabis use and age at onset of schizophrenia.
Am J Psychiatry. 2004 Mar;161(3):501-6.

Causal association between cannabis and psychosis: examination of the evidence.
Br J Psychiatry. 2004 Feb;184:110-7. Review.

[Cannabis use as a probable causative factor in the later development of schizophrenia]
Ned Tijdschr Geneeskd. 2003 Nov 1;147(44):2178-83. Dutch.

[Use of cannabis in adolescence and risk of schizophrenia]
Rev Bras Psiquiatr. 2003 Sep;25(3):131-2. Portuguese.

Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study.
BMJ. 2002 Nov 23;325(7374):1212-3. No abstract available.

[Is there a temporal correlation between substance abuse and psychosis in adolescents?]
Z Kinder Jugendpsychiatr Psychother. 2002 May;30(2):97-103. German.

Cannabis and psychosis.
Curr Psychiatry Rep. 2002 Jun;4(3):191-6. Review.

Cannabis-induced psychosis: a cross-sectional comparison with acute schizophrenia.
Acta Psychiatr Scand. 2002 Mar;105(3):173-8.

Cannabis and schizophrenia: a longitudinal study of cases treated in Stockholm County

Self reported cannabis use as a risk factor for schizophrenia in Swedish conscripts of 1969: historical cohort study

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55 Comments so far ↓

  • habsfan

    The average high school student does not have the pharmacological sophistication of knowing the difference between tincture and probably does not care what Queen Elizabeth smoked (totally irrelevant to the debate) He purchases something produced by criminal organizations who are interested in a) Selling as much weed as possible b) Introducing other drugs that will make the client a long term user. These criminal organizations are sophisticated and certainly picturing the product that they sell as harmless raises interesting questions.

    1. Most regular (during school) users are incapable of functioning in class. It is very difficult for most students to focus when they are stoned or drunk. Can’t get drunk on 5 grams of beer, though! Much harder to do at school!
    2. Legalizing and taxing may offer the libertarian hated government with added revenue stream and possibly clean up the product. In Canada, where government medical marijuana is available, most users complain that it is poor quality….So how do you regulate it. What dopeheads to you consult…BC dope is legendary, as is Quebec grown….It seems the MOB has the critical expertise, do you subcontract?
    3. Cigarettes are legal. Students must be 18 to purchase them in Quebec. Adults are therefor free to smoke (although the societal stigma have made this activity politically incorrect and it is now illegal to have a beer and a cigarette in a bar. Given that I enjoy a good Cuban cigar with a scotch, I find these attitudes and laws restrictive so I consume a wee dram and stogey outside in the yard) Health Canada has conducted “stub studies” around high schools in the Montreal area. The vast majority of cigarettes consumed by youths come from the unregulated market. That’s right, contraband cigarettes purchased through intermediaries. Now, how would this be any different if weed were legalized and government controlled. Presumably, we would still wish to encourage students to be of sound mind when studying. So since, they would not be able to purchase the weed at the official weedmart, they would revert to underworld suppliers. Same applies to other categories of hallucinogenics, opiates etc. (Ecstasy is the drug of choice among many teens…they typically start somewhere else….not jump to it).
    Given that the US sits at the bottom of the educational rankings according to the PISA exams, (google it, the 2009 results are out) bring on the pot….let the Chinese buy you out! Interesting, there is a correlation between a school’s academic performance, graduation rate etc and drug use. Spark one up for me…in an increasingly competitive world….being stoned and uneducated is the way to go!

  • Iamm

    Hello habsfan, thanks for responding.

    May I ask why aren’t the students educated about the differences? They don’t need” pharmacological sophistication” to understand the difference between juice and juice concentrate. Education, my friend. That’s beside the point though… IMO, I think it’s quite relevant to debunk the “potency” red herring. The statistics are only brought up to incite fear in the ignorant. Stop trying to use it. It’s only another example of why we cannot take you seriously. (You had spoke of this in a prior post, no?)

    Habsfan, seriously, do you know anything about supply and demand? You speak about “criminal organization” as though they were some sort of conspiracy. THEY SUPPLY WHAT’S DEMANDED! You can substitute “criminal organization” with the pharma/alcohol/nicotine/fast food/etc. industry and make the same argument. Should we ban them too? Answer: No, that thought is just silly. The people you classify in this conspiracy are only trying to find a way to make easy money in the black market. Now, we can’t just remove all the laws so don’t try to take that argument route. We can also spend days arguing ways of dissolving said “organizations” too. There are many favored opinions/options. My opinion tends to lead toward harm reduction. I tend to wonder why we accept that alcoholics may have alcoholism. Yet people who use non-alcoholic, non-pharmaceutical, tobacco-free drugs are deemed criminals. Ever hear the phrase – “Does not compute.”

    1. This is where we may have some agreement… “Adolescents” should not be using ANY sort of drug unless deemed medically necessary. Using a pot vs. alcohol quantity angle is in no way a cogent argument. Ever here of a flask? Sheesh….

    2. What could I possibly take from this? (I do somewhat agree with your first part.) We can figure out ways to walk on the moon and to geo-engineer. You are saying we can’t figure out how to properly educate about and regulate something as simple as cannabis. You must have no faith in the human race, eh?

    3. Let me reiterate – I do not condone adolescent use of drugs, even the cannabis herb. Thank you, thank you, thank you for making a statement in favor of less draconian, more common sense regulation. I must thank you again for pointing directly at a huge gaping hole in the pro-prohibition approach. At least with tobacco some can use it legally and are not in fear of para-military swat teams smashing into homes with no knock warrants… In which not all end favorably. May I ask why shouldn’t you be tossed in jail for using legal contraband (in an adolescent’s sense), because, well, what message does this send to them? Does nicotine/alcohol not demonstratively show negative aspects? Nicotine rates are down over the past few decades because of educational efforts, not through criminal justice system… ruining lives/futures. It just sickens me to death to think a “peace officer” could open fire upon an individual over something as trivial as cannabis. Disgusting.

    The following will be my only comment on your attempt to bring up the gateway theory. “L.O.L., R.O.F.L.” (Sad attempt at a joke, I know :P )

    Are you seriously trying to correlate cannabis use to low PISA exams? Not even mentioning US education and economic policy? There is no need to comment here.

    Now, what I’d like to know is… what solution do you advocate?

    P.S. Please don’t take any of my comments personally. I’m only trying to contribute to the argument playing field. Thanks for reading.

  • habsfan


    I have extensive experience in dealing with teenagers, and I can tell you that there is a correlation between the schools with a heavy drug use problem and poor academic results. Teen agers respond to clear instructions. For several years there was talk in Canada about legalizing cannabis. When asked if marijuana was legal many teenagers believe it is…..My point is that a clear message is what is needed. That is the education angle of the debate. Students are informed that the cannabis is illegal and that it is damaging to your health and ability to learn, yet they are the heaviest users. So much for education being the answer.

    Here is a thougt. Submit all producers and dealers to substantial corporal punishment and incarceration. The higher up the food chain, the more substantial the corporal punishment and the incarceration. This does not place resource chasing after users, will dry up supply and will keep drugs out of schools. No 18 yr old kid wants to get the sh@t kicked out of him because he is selling dope at the local high school.

    Here is another interesting trend….Since children under 12 cannot be held criminally responsible in Canada, street gangs are now recruiting elementary age students to distribute their drugs. How edifying!

    There are many schools whereby many students are comfortably fried by 10:30 in the morning. Recess is the worst thing that happens in these schools.
    You are correct about the nicotine trend….generally smoking is down. Unfortunately, young people are the only segment where smoking is still trendy. As I mentioned this is now another niche market for the underworld in Quebec! Most baby boomers starting kicking the habit when they realized that they would not live forever and that smoking would kill them slowly.

    Iamm, take a walk around your neighborhood high school and count the number of students having a smoke. Now, there is a very good chance that many of these are not necessarily having a Marloboro! The flask, may be an option, but my experience in the business is that it is much more discrete to spark a dube than chug some Jack. Less chance of vomit considering you have 10 minutes to get your fix.

    Singapore does not seem to have a drug problem. One of my very good friends informs me that Singaporeans seem quite happy without having to resort to cannabis, opiates etc. Yet having a drink is quite acceptable. The sentences for possession are rather harsh….Reminds me of a case, when a dutch youth was found guilty of possession of marijuana and sentenced to repeated caning and jail time. As expected, the Dutch embassy protested the “barbaric punishment”. The judge commented that Singapore, unlike the Netherlands, does not have a drug problem….and is one of the most affluent societies in the world…..

    The PISA exams are quite indicative of the proficiency of a nation’s education system and its ability to produce literate and numerate youths. This is very hard to achieve when young people are fried during the school day.

    Cheers, as a take another sip of my rather excellent grappa!

  • Iamm


    Okay, where to start… So frustrating. Your points fabricated using anecdotal information still does nothing to prove a case for blanket prohibition or to change my opinion, even slightly, on the cannabis issue. Until you can understand cannabis from a legal aspect your ignorance will continue to flourish. Are you aware of the process which deemed cannabis to be illegal? How can you sit there and type up your drivel. Have you watched or read about the propaganda used early in the 20th century? The racism and garbage science used was despicable. Please look it up. If the “Reefer Madness” type movies and yellow journalism was to be used in this day and age to argue against cannabis it would be considered comical and ridiculous. If it wasn’t for this junk the debate here wouldn’t even be.

    Again, we are in agreement that use of “any” restricted substances by teens should be discouraged. Period. I agree there should be better messages delivered to teenagers too. These messages should contain clear, unbiased, non-partisan, scientific, practical, understandable and relatable information. Lying to children only exacerbates the situation. This is clear from your Canadian teen comment. The teen hears one side of a message, and is able to easily find information to refute said message, confusion is the inevitable result. Especially when cannabis is the subject. Why should they listen to the same people who are lying to them?

    Blaming the “stupification” of students solely on perceived drug use is a poor analysis. Perhaps the education system needs to evolve to encourage students to be involved in the learning process, and discourage being zoned-out when they aren’t interested? I’ll let you in on a little secret, shhh, don’t tell anyone else… I also have extensive experience in dealing with teenagers. I was subversive, two-faced even! I was able to infiltrate “them” at one point in time. They even considered me a friend. It was called being a TEENAGER, don’t you remember being one? The perspective you had on the world and the conclusions that came about by that point of view. There were subjects in school in which I learned nothing. Not because of drug use, but because I chose to doodle in my notebook and not pay attention. There was no difference in the end result. BTW, Please get off the “What about the children” high-horse. It still doesn’t justify draconian sanctions on everyone.

    If gangs are recruiting 12 year olds it is likely a result of smart people finding loopholes within your prohibition idiocy. It doesn’t work. Why can you not understand this?

    “Here is a thougt. Submit all producers and dealers to substantial corporal punishment and incarceration. The higher up the food chain, the more substantial the corporal punishment and the incarceration. This does not place resource chasing after users, will dry up supply and will keep drugs out of schools.” <- How does this differ from current policy toward illegal drugs for the last 100 years? You advocate for the same system(or worse) even though 2/3 of Americans think it has failed? Ah, you bring up Singapore drug policy as if to justify your argument and backing it up by showing youth can still obtain cannabis. This is another very poor example, sorry to tell ya. Sentencing people to death over cannabis yet tolerate alcohol… *sigh*

    “No 18 yr old kid wants to get the sh@t kicked out of him because he is selling dope at the local high school.” <- AND THIS IS WHAT YOU ARE ADVOCATING? You sir/ma’am are a disgrace for a human being and should have the sh@t kicked out of for even contemplating this. Please, move to Singapore if you like their policies so much. You make me sick to my stomach. I refuse to continue debating your sadistic, disgusting, amoral way of thinking. Unlike you, I’m not a barbarian hiding behind a sophisticated façade. Good-bye. (Just another reason why a common sense approach will prevail.)

  • habsfan


    I am truly impressed by the quality of your argument. “You make me sick to my stomach” is a very intelligent and mature approach to addressing an argument. Your penchant for the acceptance and tolerance of cannabis is obvious and you present your case with much energy. I respected your position, although I disagreed with it.

    Sadly, like many who have difficulty with disagreement you descend into name calling and pettiness. Disagree with me, but do so intelligently. Your life experience as a teenager is an outstanding source of information and you clearly argue as a true scholar. When you cannot produce a cogent argument, you resort to name calling.

    Singapore has one of the highest standards of livin and has one of the most demanding and effective eduction systems in the world. In fact, the 1960′s and 70′s hippy era never made it there and they therefore have taken measures to isolate themselves from some of the destructive elements of this era. Of course, those who lived it and never grew up from it, or venerate the culture of the era cannot help but see nothing wrong with drug culture.