TEENAGE SCHIZOPHRENIA IS THE ISSUE, NOT LEGALITY

The Government Mistake Was to Suggest Cannabis Was Harmless

For 150 years it has been known that acute intoxication with cannabis
can induce hallucinations and delusions. However, this was thought to
be a transient effect which usually rapidly resolved itself. Then in
the late 1980s and 1990s psychiatrists like me began to see growing
numbers of young people with schizophrenia who were taking large
amounts of cannabis.

We first thought that they were self-medicating in an attempt to
ameliorate their anxiety and paranoia. However, since their families
often told us that cannabis seemed to exacerbate the symptoms, we
decided to examine this. When we followed up 119 young people who had
been diagnosed with schizophrenia, we discovered that far from being
helped by cannabis, those who continued to take the drug four years
later were three times more likely still to be hallucinating and
deluded than non-consumers.

If cannabis could make schizophrenia worse, could it have caused the
psychosis in the first place? The only way to decide is to question
large numbers of healthy people about their cannabis habits and follow
them up to see whether the cannabis consumers are more likely to
develop psychosis. Eight studies have now reported that those who
consistently take large amounts of cannabis have an increased risk of
later developing schizophrenia-like psychosis.

It is estimated that at least 10 per cent of all people with
schizophrenia in the UK would not have developed the illness if they
had not smoked cannabis, so there are about 25,000 individuals whose
lives have been ruined by cannabis.

Why are we seeing so many cases of cannabis-induced schizophrenia? A
UN report in 2006 suggested three reasons.

First, the consumption of cannabis climbed steadily across Europe over
the past four decades to reach a peak about 2002.

Second, high-potency cannabis preparations are more widely available.
Traditional 1960s herbal cannabis contained about 2-3 per cent of the
active ingredient tetrahydrocannabinol (THC); but today's skunk
varieties may contain 15 or 20 per cent THC and new resin preparations
have up to 30 per cent. Skunk is to old-fashioned hash as is whisky to
lager. You can become alcoholic by just drinking lager; but you have
to drink a lot more lager than whisky. Similarly, you can go psychotic
if you smoke enough traditional marijuana, but you have to consume a
lot more for a lot longer than with skunk.

Third, the age of starting cannabis use has been steadily lowering. It
is now commonly taken at 15 and some of the patients I see started at
12 or 13 years.

Of course, most cannabis smokers never come to any harm, just as the
vast majority of drinkers don't get liver disease. It is simply that
the more you take the greater the risk.

The frequency of cannabis consumption and the resultant psychosis in
the UK is among the highest in Europe. I am not convinced, however,
that the exact classification of cannabis is of much relevance. The
Government's mistake was rather to give the impression that cannabis
was harmless and that there was no link with psychosis.

Charles Clarke, the then Home Secretary, realised the error in 2005
and promised education and research. The benefits of education about
the risks can be seen in the US where cannabis consumption has fallen.

The UK education campaign was largely invisible, and there is still no
significant government-funded research into cannabis-induced
schizophrenia. Indeed to judge by the relative amounts of
parliamentary time devoted to fox-hunting and psychosis since 1997,
MPs have been much more interested in the mental health of foxes than
of its young citizens.