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Even More Evidence Links Marijuana to Psychosis


For those who think marijuana is harmless, researchers are suggesting people take another look. John McGrath of Queensland Brain Institute in Australia has just confirmed what many studies have concluded, that marijuana isn’t as harmless as some think.

"Compared with those who had never used cannabis, young adults who had six or more years since first use of cannabis were twice as likely to develop a non-affective psychosis (such as schizophrenia)," McGrath wrote in a study published in the Archives of General Psychiatry journal.

There have been a variety of studies as of late that have suggested smoking cannabis can double the risk of psychosis, but the British study was the first to look specifically at skunk. Skunk has higher amounts of the psychoactive ingredient THC which can produce psychotic symptoms such as hallucinations, delusions and paranoia.

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The researchers included 3,801 young adults who were born in Brisbane from 1981 to 1984. At the 21-year follow up, the participants, whose average age was about 20, were asked about marijuana use. The researchers also measured whether those in the study had psychotic symptoms.

Of the 1,272 participants who had never used marijuana, 26 or 2 percent were diagnosed with psychosis. Of the 322 people who had used marijuana for six or more years, 12 or 3.7 percent were diagnosed with the illness. Overall, 65 people were diagnosed with psychosis, according to the study. McGrath said that even those who used marijuana for fewer than three years still had an increased risk of scoring higher than those who had not.

The study also looked at siblings who both smoked pot and found that those who smoked it longer had a higher score for psychotic-like delusions than the other sibling who smoked for a shorter time.

About 2.4 million American adults have schizophrenia, according to the National Institutes of Health. The disorder often appears in men in their late teens and early 20s, while in women it generally strikes in their early 20s or 30s. It is associated with delusions, hallucinations and disordered thinking, McGrath said. It is unclear what causes the disease.

McGrath said, "the nature of the relationship between psychosis and cannabis use is by no means simple and more research is needed to examine the mechanisms at work.” What is a known fact is this is just another study confirming that long term use of marijuana can be linked to forms of psychosis.



Prohibition is a sickening horror and the ocean of human wreckage it has left in its wake is almost endless. Based on the unalterable proviso that drug use is essentially an unstoppable and ongoing human behavior which has been with us since the dawn of time, any serious reading on the subject of past attempts at any form of drug prohibition would point most normal thinking people in the direction of sensible regulation. By its very nature prohibition cannot fail but create a vast increase in criminal activity, and rather than preventing society from descending into anarchy, it actually fosters an anarchic business model - the international Drug Trade. Any decisions concerning quality, quantity, distribution and availability are then left in the hands of unregulated, anonymous, ruthless drug dealers, who are interested only in the huge profits involved. Prohibition ideology is based on lies and the 'War on Drugs' is a de facto 'war on people' (some might even successfully argue that it's a de facto race war). Prohibition has decimated generations and criminalized millions for a behavior which is entwined in human existence, and for what other purpose than to uphold the defunct and corrupt thinking of a minority of misguided, self-righteous Neo-Puritans and degenerate demagogues who wish nothing but unadulterated destruction on the rest of us!
Interesting that you failed to mention that the study also found that people with psychotic symptoms already were more likely to seek to use marijuana. This is no proof of cause and effect. We still have a chicken and the egg situation - which came first? Nor has any article on this study indicated whether the psychotic symptoms were experienced while on the drug, or significantly off of the drug. THC is a known psychotic. Cannabidiol is a known antipsychotic. And the increase of marijuana smoking in Britain has been shown to increase without a corresponding increase in the number of schizophrenics. The Brits have also concluded that it would take thousands of people to stop smoking marijuana to prevent just one case of schizophrenia. Yet one out of a hundred people are going to get schizophrenia anyway. And even with the increased risk of psychosis , marijuana is still one of the safest drugs we know. Psychosis shouldn't scare you as a side effect, doctor. There are so many FDA approved drugs with the ability to cause psychosis and wreck your body also. Benzos, cough suppressants, Chantix, etc. After 40 years of inconclusive studies designed to prove the negative effects of marijuana, can we not get past this silly demonizing of marijuana and reschedule it so that effective studies on marijuana can be done?
This is completely wrong. For one thing skunk weed is crap, and not that potent. Two weed does not make you trip out, although it does make some paranoid, I am not one of those people. I am a perfectly sane individual and laugh at this report. What about alcohol and all of the death depression and mental illness it causes? Nobody seems to care about it because it kills. No big deal I guess. Pot is harmless smoke it to realize it, studies don't mean shit. They are wrong. Think about it, What these people report is so far from the truth it's pathetic. This report makes these people who performed the study seem like morons.
The jury is in on the topic of cannabis, conclusion: It’s a safe and effective medicine! And guess what? Just like ANY medicine on the market today, kids should not do them. How about opiates, are opiates OK for teenagers? Alcohol? These two KILL teenagers! Shall we start up prohibition again? Outlaw all opiates for patients? There’s only one reason this PLANT is illegal: Economic interest/monopoly. FEB 1938 Popular Mechanics writes: http://www.druglibrary.org/schaffer/hemp/history/newbilln.htm Now it’s the pharmaceutical giants that are fighting cannabis. BTW, That’s 38 people out of 1272 that were diagnosed with psychosis, 12(.009%) of these psychotics consumed cannabis. How many of the 12 already had the disease, or used other substances, or lied? They are psychotic, and at best teenagers. What other subtances did the “teenagers” admit to consuming? This is a “survey” of no validity IMO, and a direct insult to “real science”.
Results reported are clearly biased if you run the math. What this study showed me is that 65/3801 people were diagnosed with psychosis, which happens to be 1.7% of the population. Of that number, people who never smoked weed had a higher (2.0%) rate of psychosis than the total population. Of that number, the 2207 people who smoked weed but not for more than six years had a 1.2% rate of psychosis, lesser than the population. You only get a higher percentage (3.7%) with a much smaller group (322 total), and the study gives no indication of how much and what quality of weed are involved. It also does not account for any other drug use (cocaine, heroin, meth, etc) or environmental factors that might've contributed to the psychosis. Poor scientific research and reporting that is clearly politically or personally motivated.
OK, then where are all of the psychotics? It is estimated that 14 million use cannabis daily in the US. So where are the bodies? I don't see 5.1 million psychotics running amok... Is this going to be one of those studies like the testicular cancer story? The rate went from 0.06% to 0.12%. Not a lot to worry about. Reminds me of the 70's man boob scare...smoke pot = get man boobs. Still haven't seen that yet. Another study in a long line of studies that make little reference to reality. Call me when you have something important to say.
Is Obama, Bush and Clinton going to develop schitzopfrenia now? How about HALF the world that has tried marijuana at some point? 3.5 billions psychotics....watch out!
This study is botched. As a psychology student, even I can tell you there is a LOT that was NOT taken into account, such as 1) Whether the person had done any other drugs besides marijuana 2) Whether the person has any family history of mental illness or even 3) if the person had been tested for mental illness before starting to smoke marijuana. It is not new knowledge that those that *already have* mental illnesses such as schizophrenia are more likely to partake in drugs and alcohol. Sounds like you guys are just trying to spin that the other way around.
"even more"? it's pretty well known that practically any drug used by young brains will cause developmental damage. this just proves that we need to legalized and regulate cannabis just like we do alcohol and tobacco so that teens won't have such easy access to marijuana. so what evidence do you have that proves pot is dangerous to adults? seriously, I dare you to find something. go on, I'll wait.