The Guardian (UK) reports that a new study of habitual marijuana users run a higher risk for psychosis, which in younger smokers could result in a 25% increase in the onset of mental illness:

Some young people who smoke cannabis are at real risk of developing psychotic mental illness, according to a major study announced yesterday.

The new survey of 2,500 young people aged 14 to 24 will be discussed at the start of an international conference today on cannabis and mental health convened by the Institute of Psychiatry in London.

It shows that regular cannabis smoking increased the risk of developing psychosis by 6% over four years.

But there was a substantially greater impact on young people who had already been identified by psychiatrists as having the potential to become psychotic. Regular cannabis smoking raised their risk of developing psychotic mental illness by 25%.

This new study will have an impact on the debate raised by the challenge to California's medicinal-marijuana use law at the Supreme Court, although it has no impact on the legal issues at play there. This dispels the prevailing notion of marijuana as a benign intoxicant. Although the study doesn't put it in the same category as heroin or crystal methamphetamine, any drug having a 6% side effect of psychosis would get pulled from the market, let alone a 25% increased risk with younger users.

Of course, the researchers who performed this study at Maastricht University in the Netherlands claim that these significant side effects argue for marijuana's legalization, so they can then warn people not to use it:

One of the authors of the study, carried out by researchers from the Netherlands, said that although cannabis triggered psychosis in a minority of people, this was a good reason to legalise it, not ban it, so that government can promote advice and information, as it does on alcohol.

Jim van Os, a professor in the department of psychiatry and neuropsychology at Maastricht University in the Netherlands, where cannabis is legal, said a ban would be hard. "It is going to be very difficult to tell the whole Dutch population to stop using cannabis because it is bad and you will develop psychotic illness. But perhaps it is better to say if you have a family history or mental instability you are perhaps particularly at risk of negative consequences of cannabis use.

These days, in the Netherlands at least, if you have a family history of mental instability, chronic cannabis use is the least of your worries. You'd be lucky to survive childbirth if you're unfortunate enough to be born at the Groningen Academic Hospital. Beyond that silliness, an argument for legalizing a drug precisely because it has significant risk to cause psychosis merely to educate people about its dangers sounds like the worst kind of circular thinking. Why wouldn't the Netherlands be able to educate its citizens about marijuana's dangers apart from its legalization? And if it requires legalization to spread the truth about its side effects, why not just legalize heroin and crystal meth as well?

Like so much of the rhetoric on both sides of the marijuana debate, this appears to be a lot of smoke designed to hide the facts. The Maastricht study reveals some significant dangers to marijuana users, if the methodology holds up. The focus should remain on the science instead of the psychobabble used by reefer apologists.

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