CANNABIS SMOKERS 'ARE TAKING HUGE RISK OF PSYCHOTIC ILLNESS'

Cannabis users are 40 per cent more likely to develop a psychotic
illness than non-users, a study has found.

Heavy users are more than twice as likely to suffer mental illness,
according to a group of British academics, who calculate that about
one in seven cases of conditions such as schizophrenia is caused by cannabis.

The warnings come as the Prime Minister and the Home Secretary
signalled that the "softly softly" era for cannabis may be coming to an end.

Gordon Brown said last week that the Home Office would be consulting
on whether it had been right to downgrade cannabis from a Class B to
a Class C drug in 2004. Jacqui Smith, the Home Secretary, is to ask
the Advisory Council on the Misuse of Drugs to review the evidence.

The paper, published in The Lancet, is written by a group of seven
psychiatrists and psychologists from Bristol, Cardiff, London and Cambridge.

They have pooled the findings from 35 studies in a number of
countries, including the United States, Germany, the Netherlands,
Sweden and Britain, and concluded that there is "a consistent
association between cannabis use and psychotic symptoms, including
disabling psychotic disorders".

They admit that they cannot be certain that the association means
that there is a simple cause and effect, but say that policymakers
"need to provide the public with advice about this widely used drug".
They go on: "We believe there is now enough evidence to inform people
that using cannabis could increase their risk of developing a
psychotic illness later in life."

As well as looking at psychotic illness, they looked for evidence
that cannabis could cause affective disorders such as depression,
anxiety and suicidal thoughts. Almost all the studies point towards
an increased incidence of such disorders. The evidence is less
strong, the writers say, but is still of concern.

The study was welcomed by many experts, but others counselled
caution. Leslie Iverson, of the University of Oxford, a member of the
advisory council, said: "Despite a thorough review the authors admit
that there is no conclusive evidence that cannabis use causes
psychotic illness. Their prediction that 14 per cent of psychotic
outcomes in young adults in the UK may be due to cannabis use is not
supported by the fact that the incidence of schizophrenia has not
shown any significant change in the past 30 years."

But Robin Murray, of the Institute of Psychiatry at King's College
London, called it "a very competent and conservative assessment of
what research studies tell us about the relationship between cannabis
and psychiatric disorders".

He said that the risk could be even higher then the authors had
estimated, because the cannabis available today was stronger than in
the past. "This report cannot tell us whether the risk is higher with
the use of the skunk-like preparations which are now widely
available, and which contain a higher percentage of
tetrahydrocannabinol," he said. "My own experience suggests to me
that the risk with skunk is higher. Therefore, their estimate that 14
per cent of cases of schizophrenia in the UK are due to cannabis is
now probably an understatement."

Martin Barnes, chief executive of Drugscope and also a member of the
council, said: "Cannabis is not harmless, and although it has been
known for some time that the drug can worsen existing mental health
problems, it may also trigger the onset of problems in some people."

"The challenge is to ensure that information on cannabis use and the
associated risks is understood by teachers and health professionals
working with young people and conveyed in ways that young people will
listen to. Since reclassification, cannabis use has continued to
fall. We need to make sure this trend continues."

Marjorie Wallace, chief executive of the mental health charity SANE,
said: "The Lancet report justifies SANE's campaign that downgrading a
substance with such known dangers masked the mounting evidence of
direct links between the use of cannabis and later psychotic illness.
The debate about classification should not founder on statistics but
take into account the potential damage to hundreds of people who
without cannabis would not develop mental illness.

"While the majority can take the drug with no mind-altering effects,
it is estimated that 10 per cent are at risk. You only need to see
one person whose mind has been altered and life irreparably damaged,
or talk to their family, to realise that the headlines are not
scaremongering but reflect a daily, and preventable, tragedy."

Martin Blakeborough, director of the Kaleidescope Project and a
member of the council, said that it would be a waste of public money
for the same panel, with the same evidence, to review the issue
again. "There is significant danger in reviewing cannabis again, as
it takes experts' minds off more important issues. Classification
itself, although important, is not as urgent as the increasing
epidemic of hepatitis B and C among drug users and the wider
community, or the increase of stimulant drugs in our community."