Independent | What is really needed in dealing with cannabis is
a “tobacco moment”, as with cigarettes 50 years ago, when a majority of
people became convinced that smoking might give them cancer and kill
them. Since then the number of cigarette smokers in Britain has fallen by two-thirds.
A depressing aspect of the present debate about cannabis is
that so many proponents of legalisation or decriminalisation have
clearly not taken on board that the causal link between cannabis and psychosis has
been scientifically proven over the past ten years, just as the
connection between cancer and cigarettes was proved in the late 1940s
and 1950s.
The proofs have emerged in a series of scientific studies
that reach the same grim conclusion: taking cannabis significantly
increases the risk of schizophrenia. One study in The Lancet Psychiatry
concludes that “the risk of individuals having a psychotic disorder
showed a roughly three times increase in users of skunk-like cannabis,
compared with those who never used cannabis”.
As 94 per cent of cannabis seized by the police today is super-strength skunk,
compared to 51 per cent in 2005, almost all those who take the drug
today will be vulnerable to this three-fold increase in the likelihood
that they will develop psychosis.
Mental health professionals have long had no doubts about the danger.
Five years ago, I asked Sir Robin Murray, professor of psychiatric
research at the Institute of Psychiatry in London, about them. He said
that studies showed that “if the risk of schizophrenia for the general
population is about one per cent, the evidence is that, if you take
ordinary cannabis, it is two per cent; if you smoke regularly you might
push it up to four per cent; and if you smoke ‘skunk’ every day you push
it up to eight per cent”.
Anybody wondering what happens to this 8 per cent of the skunk-smoking population should visit any mental hospital in Britain or speak to somebody who has done so.
Dr Humphrey Needham-Bennett, medical director and consultant
psychiatrist of Cygnet Hospital, Godden Green in Sevenoaks, explained to
me that among his patients “cannabis use is so common that I assume
that people use or used it. It’s quite surprising when people say ‘no, I
don’t use drugs’.”
The connection between schizophrenia and cannabis was long
suspected by specialists but it retained its reputation as a relatively
benign drug, its image softened by the afterglow of its association with
cultural and sexual liberation in the 1960s and 1970s.
