It is the world's oldest euphoric drug, long viewed by any liberal worth their salt as a victim of unfair drug laws. The notion that a spliff is a safer, sweeter means of relaxing than a pint has over the years spread way beyond its traditional student constituency to every corner of society. But two years after the Government listened to these voices and the law was relaxed, its safety is under question as never before. A report to be published within the next few weeks is expected to confirm what some psychiatrists have been warning for years. That cannabis, reputedly taken by Queen Victoria to banish her period pains, may be driving its users " many of them children " insane.
Charles Clarke, the Home Secretary, indicated last week that following the report from the the Advisory Council on the Misuse of Drugs, he is planning a U-turn on David Blunkett's reclassification of cannabis in 2004. Clarke is expected to take cannabis from Class C back to Class B status, with tougher penalties for possession. But is cannabis really so dangerous?
Cannabis is the most widely used illegal drug in the UK, and the impression that it promises a risk-free high was increased by Mr Blunkett's move. But in the last two years, evidence has strengthened that the drug that inspired the hippie generation to make love not war is a trigger for psychotic delusion that may confine a small minority of vulnerable users to a lifetime in mental institutions.
There is nothing new about 'reefer madness' and the exact role of cannabis in psychosis is disputed by psychiatrists. But two developments have increased professional anxiety about its dangers.
First, the cannabis available on the streets is stronger than it was a two or three decades ago. Much of it is 'skunk', a high- octane version of the more benign 'weed', often cultivated hydroponically (without soil) indoors, under lamps where it is specially bred to increase the content of the main psychoactive ingredient, tetrahydrocannabidinol, or THC. A cannabis joint today may contain 10 to 20 times more THC than the equivalent joint in the 1970s. All drugs carry a risk of side effects and the more powerful the drug the greater the risk that some users will suffer harm. Cannabis is no exception.
Second, the age at which young people begin experimenting with cannabis has decreased. The younger a person is, the more susceptible they are to drugs of all kinds. Experts believe there is a particular risk of damage to developing brains from psychoactive drugs. Research in Australia has shown that the age of first cannabis use has declined since the 1970s from the early twenties to the mid-teens. In the Netherlands, the European country with the most liberal drugs policy, it is between 13 and 14 and in the UK it is between 15 and 16. Studies in the UK show that two in five 15- year-olds have tried cannabis " more than in any other country in Europe. The risk of the drug triggering psychosis may increase with decreasing age.
A psychotic episode can involve hallucinations, fantasies and a loss of touch with reality which may last days, weeks or months and can be very frightening. Although it is possible to have a single episode without recurrence, the risk of attacks is increased after the first.
Robin Murray, professor of psychiatry at the Institute of Psychiatry, has sounded the loudest warnings about cannabis, but even he says: 'It is obviously ridiculous to say everyone who smokes cannabis is going to become psychotic. Even in our studies of adolescents, 90 per cent of those who smoked cannabis did not go on to develop psychosis.'
But he points to mounting evidence that the drug can trigger psychosis in vulnerable individuals. The big question now is: who is vulnerable? A study by the Institute of Psychiatry published in the journal Biological Psychiatry last May suggested that people with a variant of the gene COMT, carried by 25 per cent of the population, had a five times higher risk of psychosis if they smoked cannabis. …