The below article reports on the correlation between marijuana use and psychotic illness with a special focus on schizophrenia. See also the NIDA for more information on what is known about the use of marijuana. Much of this information we will cover inclass later this week and next. Click here for more information on this issue and other information on marijuana from the NIDA web site.
Researchers say they have the strongest evidence yet that using cannabis increases the risk of later developing psychotic illnesses such as schizophrenia.
On average, cannabis smokers have a 41% greater chance of suffering from such disorders than those who didn't inhale, the new study finds. And the likelihood increases with increasing cannabis use, with heavy users - who smoke daily - three times as likely as non-users to develop psychotic illnesses.
Cannabis is the most commonly used illegal drug in the world. In the UK and the US, for example, around 40% of young adults have used cannabis, according to government research.
Previous research has suggested a link between cannabis and schizophrenia-like symptoms such as paranoia, hearing voices and seeing things that are not there. But the possible association "has been an issue of tremendous debate and controversy for a long time", says Rick Rawson, a professor at the University of California in Los Angeles, US. "The science gets all mixed together with all the ideological views [about the drug]."
Now, researchers in the UK have reviewed 35 studies on the long-term effects of cannabis use in Europe, the US and Australasia and say the drug does in fact appear to be linked with an increased risk of psychosis. The original studies lasted from one to 27 years.
Causal link?Because people with pre-existing mental health problems may be more likely to take drugs in the first place, the researchers excluded data from those already showing signs of psychotic illness. Still, they found an increased incidence of psychosis in cannabis users, suggesting the drug may somehow cause such disorders, they say.
"Although you cannot be certain that the cannabis is causing this increase in risk, we think there is enough evidence to warn people," team member Glyn Lewis of the University of Bristol in the UK told New Scientist.
If cannabis does cause psychosis, it could account for at least one in every seven cases of diagnosed psychotic illness, the researchers say.
"There is a very good reason to be concerned," says Shaul Hestrin of Stanford University in California, US, who is investigating how cannabinoids affect brain cells. He says the evidence of a causal link in this latest study is "very convincing" but adds that even better evidence may come once scientists understand how cannabis actually changes the brain.
Rawson agrees: "The big question is how to determine who's at risk."
The British government is now reviewing the classification of cannabis, which is currently a Class C drug. It may be reclassified as Class B, which means users could begin to do jail time for possession.
"Clearly the health risks are only some of the factors that are taken into account when people consider the legal classification of drugs," Lewis says. This latest study was funded by the UK Department of Health, and Lewis said the results have been given to the UK Home Office.
Journal reference: The Lancet (vol 370, p 319).
17 comments:
Wow. Just one more reason to stay off marijuana. This explains so much about mental problems.
Interesting info. What's scary though, is how many people can, and are going to, get disorders. That's a lot of crazy smokers.
Yes this is a clear warning, however, understand that any causal link is unclear. There are plenty of people who take this drug and do not develop schizophrenia.
BOTTOM LINE: it comes down to vulnerability. That is the key. The safe bet of course is to avoid these kind of drugs, especially if you have psychotic disorders in the family.
Alex is totally right. If for some reason people don't have enough reasons to stay away from marijuana, this is just another great one. Schizophrenia personally scares me- hearing voices is never a good thing- and i have no intention of becoming crazy. Hopefully they'll create that new law with classifying it as a class B drug and putting people in jail for possession.
Another point to keep in mind (as was mentioned in class today) that the marijuana that was used decades ago is very different from what it is today. Today's marijuana has been modified to be much more potent.
I think those people who want to legalize marijuana now will have a much tougher job will all this new research being done on it. That's definitely not a bad thing though, and I'm pretty sure it will never escape its illegal status anyway.
Strictly psychologically speaking, criminalizing drugs has not shown to be affective with respect to lowering the frequency of use. Education appears to be the most powerful way to curb drug abuse.
"heavy users - who smoke daily - three times as likely as non-users to develop psychotic illnesses."
Well, as a nonuser how likely am I to develop a psychotic illness? I don't know the numbers but I imagine the likeliness of me developing a psychotic illness is pretty low, if you multiply it by three does it get significantly bigger? I dont mean to be dogmatic but that statement seems a bit laughable.
I think the legalization of marijuana is comparable to gum use in school. In general, elementary schools and middle schools have rules against gum, but in high schools you can chew gum. I can't say I know for a fact but isn't there less gum stuck under desks and less chewed in high school?
Conor,
Interesting points. Regarding the increased risk/probability, of course if you have a close to zero percent chance of suffering schizophrenia (something that would be difficult to be sure of), making it 3 more times more likely may still make it basically just as likely than without drug use. The problem is, however, schizophrenia is not the only psychotic disorder. What's more, there are degrees of such disorders. It is not an all or nothing issue.
Crap.
Paul?
well obviously.
i don't think people need a study about this.
basically stay off drugs and you'll be good to go, i could know that WITHOUT any study!
the only people who seem like they would be in denial about this are the people who use themselves. Just like you say how users are usually in denial...
while i wouldn't go so far as to deny a link between smoking pot and mental illness, i am hardly convinced that such relationship exists to that degree. besides im not so sure i believe smoking pot "causes" mental illness. i believe that those who are genetically predisposed to mental illness do, in large part constitute what we may define as heavy smokers ( this to me seems much more logical, as those with serious mental problems would have much more reason to want to escape reality).
secondly when this study claims to show a relationship between smoking marijuana and psychotic disorders, how can we isolate pot smoking as the sole variable in this study influencing mental illness? ridiculous if you ask me. its not as though such human subjects are kept in a cage with the intent to minimize outside influence(enviroment, upbringing not to mention that most cannabis smokers are likely involved in the use of other drugs).
and on top of these things, do we really know the genetic factors that put one at risk for psychotic disorders? if we dont know the origin of these conditions, how can we know that those who were so inclined to smoke pot weren't more likely to be genetically predisposed to mental illness. in my humble oppinion, this data seems inconclusive at best.
Joey,
Great questioning here! Just to add a response to Joey's post, doctors and researchers can get an idea of one's genetic predisposition to a psychological disorder by analyzing one's family record. What's more, some genes are known to be associated with various disorders as well. Thus it is not an artificial measure.
It is difficult to know whether or not a brain that will develop a psychotic disorder is more prone to use marijuana OR if marijuana can trigger the vulnerability. The statistics are clear however that they co-vary.
I do agree mr caro, that to some degree we can assess a persons likelihood of developing mental illness based on heredity. i never knew that such genes have been identified however! but yet even so, as you have said only some of the genes associated with personality have been discovered, and heredity is only accurate to some degree. also as you have stated, such statistics for cause and effect do vary. with such relative uncertainty, i would think it a stretch to identify cannabis smokers as being 3 times more likely to develope any psychotic disorder.
I wonder if this will make any doctors reconsider prescribing marijuana for medical use or if this link isn't definite enough to affect that.
Jake,
That is a GREAT question. Often the marijuana that is prescribed by doctors (often in for cancer patients going through Chemotherapy which causes severe nausea) is given in smaller quantities. The idea here is not to get high but to cut back the negative effects from therapy.
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