I only indirectly referred to a recent Australian study that said cannabis use in teenagers was associated with earlier onset of psychosis, and that alcohol use wasn’t. I see now that it was in fact a meta-analysis of other studies.
The most surprising thing I saw the authors say appeared in the ABC report:
"The risks for older people is about double, so instead of having a 1 per cent chance of developing schizophrenia you are probably likely to have about a 2 per cent chance," he said.
"But for young people who smoke cannabis regularly, instead of having around a 1 per cent chance of developing schizophrenia during their life, they will end up with something like a 5 per cent chance of developing schizophrenia."
I was a bit puzzled, with such a high increase in risk for teenager smokers of developing schizophrenia, that the authors were still hedging their bets on whether you could say cannabis caused their illness.
Anyway, here’s another just published study relevant to causation, and this one followed real people to see what happened:
Interesting. Of course, as I mentioned in my previous post, nothing annoys cannabis smokers more than the studies that keep indicating the connection between their habit and a debilitating disease, especially for those who start smoking young. See the comments following that Physorg at the above link for some examples. It’s such a shame how the evidence keeps piling up against them, though. (Ha.)The study took place in Germany and involved a random sample of 1,923 adolescents and young adults aged 14 to 24 years.
The researchers excluded anyone who reported cannabis use or pre-existing psychotic symptoms at the start of the study so that they could examine the relation between new (incident) cannabis use and psychotic symptoms.
The remaining participants were then assessed for cannabis use and psychotic symptoms at three time points over the study period (on average four years apart).
Incident cannabis use almost doubled the risk of later incident psychotic symptoms, even after accounting for factors such as age, sex, socioeconomic status, use of other drugs, and other psychiatric diagnoses. Furthermore, in those with cannabis use at the start of the study, continued use of cannabis over the study period increased the risk of persistent psychotic symptoms
There was no evidence for self medication effects as psychotic symptoms did not predict later cannabis use.
3 comments:
I'm afraid the study you refered too doesn't say anything about causation only that it is an environmental risk factor. But it doesn't take much common sense to know that young developing brains shouldn't be swamped by drugs of any kind including alcohol or tobacco.
I am new to your blog so I apologise if I have misinterpreted you post, but that study in no way justifies the absurdity of our drug laws. That the most dangerous drug, and the most popular, alcohol is legal yet a relatively benign drug like cannabis is subject to criminal sanction is frankly ridiculous. Such laws are an extraordinary waste of public resources. I don't want my hard earned, and grudgingly paid tax dollars used to accommodate some harmless stoners. The criminality of their suppliers is a product of the same stupid laws.
Disclosure: I am a smoker, regular drinker and occasional cannabis user none of which I used before the age of 20. I believe all drug abuse is a health issue and is properly the remit of health professionals. What you choose to consume is between you and your god, and if you abuse it, doctor and family. The negative for the rest of us, the vast criminal industry associated with the illicit drug trade is a product of legislation, not the drugs. And governments can fix that. And it is cheap. Simply repeal the laws.
Given that you're fairly interested in the subject, I'm not sure if I'm adding anything new here but I remember that for some time, even though the correlation between cannabis use and mental illness was known, scientists weren't sure which way the direction of causation went.
Some suggested that those with the biochemistry of their brain predisposed to cannabis dependence also had something unique to their brain that made the 'high' from cannabis more intense and therefore saw them use cannabis more frequently, and become long term users. That, they suggested, might be why the link was there: not because the cannabis caused their mental illness but because their mental illness predisposed brains to keep loving smoking cannabis whereas those with normal brain chemistry were more likely to give up the habit.
I suspect that's why the first studies authors were not drawing such a link from their work - it's because they know that the other studies (like the second study you cite) are the only ones that allow one to draw that kind of conclusion.
It really doesn't matter. Cannabis has been smoked widely for a century or more, and less widely for all history before that, and the connection between mental illness and smoking it is so tenuous that we need large-scale statistical studies to notice it.
What's rather more obvious, though, is the appalling consequence of prohibition. It takes much less study to spot drive-by shootings or the sort of hell on earth that is Mexico.
Legalise all drugs, tax and regulate them like alcohol. As with booze, prohibition is far worse than any of the consequences of partaking.
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