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23 Jan 2004 00:00
Psychiatrist Robin Murray had never really planned on studying the effects of cannabis on mental health. Rather, he found himself falling into it after noticing that some of his patients, who had been gradually climbing out of the well of schizophrenia, were having relapses after smoking the occasional spliff.
“Day in, day out, I was going to either my outpatient clinic or my inpatient unit and we’d have a patient who would do brilliantly,’’ Murray says.
If they did particularly well, the patients would be allowed to go out for the evening, to enjoy themselves.
“The next morning [they] would be psychotic, hearing voices and quite deluded again.’’ And whenever this happened, there was one main suspect — the patient had probably smoked cannabis the night before.
Anecdotes like this will only serve to increase the furore currently going on in Britain about cannabis.
It was these concerns that led Murray, a professor of psychiatry and one of Britain’s leading experts on mental health, to investigate the relationship between cannabis and mental health. What he found was that cannabis almost always exacerbated symptoms of psychosis in people who were already suffering from any mental health problems.
At that point, Murray began to look deeper. “It’s a bit like saying, “Well, if people with chronic bronchitis smoke, this is not good for their chronic bronchitis’,’’ he says. “Then you begin to think, could smoking contribute to developing chronic bronchitis in the first place? Then we started thinking about the question of whether cannabis could contribute to the onset of [psychosis].’’ Murray’s latest work echoed the results of previous research by one of his colleagues, lecturer Louise Arsenault.
In November 2002 Arsenault’s team published her results in the British Medical Journal.
“The conclusion was that, if you took cannabis at age 18, you were about 60% more likely to go psychotic. But if you started by the time you were 15, then the risk was much greater, around 450%,’’ says Murray.
The research also showed that if children with quasi-psychotic ideas (in other words, they thought that other children were ganging up against them or they heard voices) took cannabis, they were more vulnerable to mental illness in later life.
All of this provided evidence that there was a link between cannabis and the onset of psychosis. But it did not explain what cannabis was actually doing in the brain. Indeed, the physiological effects of cannabis are not fully understood.
“The brain produces substances rather like cannabis which are part of normal brain function,’’ says Murray. “One of the reasons why we get an effect from cannabis is because there actually are cannabinoid receptors in the brain. We suspect that the reason why cannabis is related to psychosis is that the cannabinoid receptors are closely related to other receptors called dopamine receptors.’’ All drugs that increase the brain’s dopamine levels (cocaine for example), are known to increase the chances of having a psychotic episode. Indeed, the drugs that psychiatrists use to stop the episodes block these receptors.
So will the reclassification of the drug next week mean a sudden rise in cases for those like Murray?
Murray says he is agnostic about the issue. “To be frank, in south London, it doesn’t matter what the classification is. People who want cannabis can get it; it is readily available,’’ he says.
“What I think is much more important is that the public should know that cannabis is a drug.
“Many of our patients, when we say to them, ‘Are you taking any drugs?’, say, ‘No, I would never touch drugs.’ Then you say, ‘What about cannabis?’ ‘Oh, yes’, comes the reply. Of course they take cannabis.
“I’m not saying that the reclassification shouldn’t go ahead. What I’m saying is that ministers and others, when they talk about cannabis should say that a few puffs here and there, a couple of spliffs is not going to do you much harm, but taking daily cannabis for a number of years will indeed increase your risk of schizophrenia.’’
Murray compares the dangers of cannabis to those of alcohol.
“Somehow people know that a glass of wine or an occasional beer is different from taking a bottle of whisky every day for five years,’’ he says. — Â
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