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  1. torachi
    People who smoke pot are more likely to develop a psychotic illness such as schizophrenia earlier than those who do not use marijuana, according to a new analysis.

    The results are published online in the Archives of General Psychiatry.

    The researchers analyzed 83 studies comprising 8,167 people with a psychotic illness who used marijuana or other psychoactive substances and 14,352 with a psychotic illness who did not. Those who used marijuana were close to three years younger when they developed a psychotic illness such as schizophrenia compared with those who did not use marijuana.

    People who used any type of illicit substances (including, but not limited to marijuana), were two years younger when they were diagnosed with a psychotic illness than their drug-free peers. Alcohol use had no bearing on the age of onset of psychotic illness, the study shows.

    “It is increasingly clear that marijuana is a cause of schizophrenia, and that the schizophrenia caused by cannabis starts earlier than schizophrenia with other causes,” study researcher Matthew Large of Prince of Wales Hospital in New South Wales, Australia, says in an email. “Young people are at particular risk.”

    Marijuana’s Role in Psychotic Illness

    Exactly how marijuana use affects risk of psychotic illness is not fully understood, but “marijuana, when smoked, produces hundreds of chemicals, over 50 are psychoactive,” he says.

    “There is not so much evidence for the widely held view those patients self-medicate with marijuana,” he says. “Marijuana smoking almost always comes before psychosis and few patients with psychosis start smoking [marijuana] for the first time.”

    More than 80% of the patients in the study had schizophrenia, but there were some other forms of psychosis identified among marijuana users. “The picture looked similar irrespective of the type of psychosis,” Large says.

    Christoph U. Correll, MD, medical director of the Recognition and Prevention Program at the Zucker Hillside Hospital in Glen Oaks, N.Y., says that “marijuana usage can contribute to psychiatric disorders, but many people use it and don’t have a psychiatric disorder.”

    More than 16 million people in the U.S. use marijuana on a regular basis, and many of them began using in their teenage years, according to information cited in the new report.

    Perhaps marijuana use is one of the factors that contribute to the development of a psychotic illness among people who are genetically predisposed to such illness, Correll says.

    When asked if he thought the marijuana was the chicken or the egg, he says: “I think it is a mixture. Some people affected by illness may choose pot to cope with symptoms, but at least for a subgroup, use of pot at an earlier age may hasten the onset of psychotic illness.”

    The message is clear, he says.

    “Try to use illicit drugs as little as possible,” he says. “There is a chance that you may have a genetic predisposition for a psychiatric disorder and this can lead to an earlier outbreak or conversion to psychosis than would have happened otherwise.”

    By Denise Mann
    WebMD Health News
    Feb. 7, 2011



  1. TooFastTim
    I don't buy it, sounds like plain propaganda weed does not make people crazy publishing an article that represents a little I've 8000 people as hard evidence is irresponsible and flat wrong

    x"marijuana use almost always comes before psychosis" that's a very broad generalization
  2. Terrapinzflyer
    The pdf of the paper has been uploaded to the archives HERE

    From the introduction:
  3. Phenoxide
    Seems kind of a weird statement to make seeing as that's not the conclusion this study reaches at all. All that they've suggested is that of individuals that develop a schizophrenic illness, those that are cannabis users tend to present symptoms slightly earlier. That is not an indication for or against cannabis causing schizophrenia.

    All it suggests to me is that cannabis use exacerbates and accelerates the pathology of an underlying psychological condition. The extent to which it accelerates the condition seems rather small too if the non-cannabis users on average present symptoms only a couple of years later. That's a rather weak argument for recommending abstention compared to the substantially reduced life expectency of a tobacco smoker for example.

    That suggests that the pathology of schizophrenic conditions commences only with the first bout of psychosis. I'm sure anyone with a friend or family member suffering from this condition will know is not necessarily the case. There are often indications in the personality or behavior that suggest someone isn't in the best of mental health even before psychosis is patently present. Escalating drug use is one such indication in my opinion.

    I'd agree that there is a lack of evidence supporting the self-medication hypothesis, but I don't recall seeing a scientific study that successfully untangles the complex cause and effect relationship between mental illness and drug use.
  4. chaos69
    Yeah I know at least with bipolar people who develop bipolar as adults usually had certain personality traits not unlike ADHD as kids. It just doesn't develop into a full blown mental illness until much later.

    Also most people first experiment with weed in high school but schizophrenia doesn't usually come out until late teens early 20's so of cause people that smoke weed likely smoked it first. They also likely drank milk before they got sick too doesn't mean milk caused it.
  5. Finn Mac Cool
    Cannabis use 'raises psychosis risk' - study

    Using cannabis as a teenager or young adult increases the risk of psychosis, a report suggests.


    The study published in the British Medical Journal involved tracking 1,900 people over a period of 10 years.
    Although the link between cannabis and psychosis is well-established, it had been unclear whether cannabis triggers the disorder.
    This research strongly suggests that cannabis use comes first, rather than people taking it for their symptoms.
    The research was led by Professor Jim van Os from Maastricht University in the Netherlands, and included researchers from the Netherlands, Germany, Switzerland and the UK.

    They excluded anyone who reported cannabis use or pre-existing psychotic symptoms at the start of the study, which took place in Germany.
    The participants in the study, aged between 14 and 24, were assessed for cannabis use and psychotic symptoms at three points over a 10-year period.
    It found that cannabis use "significantly" increased the risk of psychotic symptoms, even when other factors such as socio-economic status, use of different drugs and other psychiatric conditions were taken into account.


    Sir Robin Murray, professor of psychiatric research at the Institute of Psychiatry, said the study added "a further brick to the wall of evidence" showing that use of traditional cannabis is a contributory cause of psychoses like schizophrenia.
    He said it was one of 10 prospective studies all pointing in this same direction.
    However it did not answer the question of whether skunk and other potent types of cannabis carried a higher risk of psychosis than traditional resin and marijuana, he added.
    Peter Kinderman, professor of clinical psychology at the University of Liverpool, agreed the study offered more evidence of the psychotic risks from cannabis.
    Three years ago the Labour government reclassified cannabis up to Class B from C - against the advice of its own drug advisers who said cannabis played only a "modest" role in the development of psychotic illnesses.

    2 March 2011


    Cannibas and psychosis: Your stories.
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