CANNABIS DOUBLES CHANCE OF PSYCHOSIS

PEOPLE who smoke cannabis regularly more than double their risk of
developing psychotic illness later in life, according to research that
calls for increased awareness of the dangers of the drug.

Researchers found that among all cannabis users, including social and
habitual users, the lifetime risk of psychotic illness increased by 41
per cent.

More than one third of Australians over 14 years of age have smoked
cannabis, or marijuana, at least once in their life and one in 20 have
used the drug in the past week, according to figures on drug use from
the Australian Institute of Health and Welfare. Of the 1.8 million
Australians who have recently used cannabis, one in six use it every
day and a further one in five use it every week.

The study found the increased risk for psychotic illness was relative
to the dose. Those who smoked cannabis regularly were at an increased
risk of between 50 per cent and 200 per cent of developing
schizophrenia and disorders with symptoms including hallucinations or
delusions.

This also suggested that stopping cannabis use would decrease the
risk, said the lead author, Dr Stanley Zammit, a psychiatrist from
Cardiff University and Bristol University in Britain.

Previous studies have had trouble unravelling the link between
cannabis use and psychotic disorder. Smoking the drug could be a
symptom of psychotic illness, rather than a cause, the research found.
The researchers re-examined data from 35 international studies on
psychotic illness and cannabis use involving more than 100,000
participants. Factors such as pre-existing mental illness, the use of
other illicit drugs, IQ and social class were filtered out of the
sample to try to isolate the effect of cannabis.

Dr Zammit said there was now sufficient evidence to warn young people
that using cannabis could increase their risk of developing psychotic
illness later in life, despite a lack of evidence to confirm a
cause-and-effect relationship.

The risk was relatively low but significant, he said.

One in 100 people had a chance of developing severe psychotic illness.
That risk increased to 1.4 in 100 if they had ever smoked cannabis.

In an accompanying comment, Merete Nordentoft and Carsten Hjorthoej,
of the department of Psychiatry at the Copenhagen University Hospital,
said cannabis had long been considered a harmless drug and its
potential long-term effects on psychosis had been overlooked. "There
is a need to warn the public of these dangers, as well as establish
treatment to help young, frequent cannabis users," they wrote.

Cannabis accounted for 45 per cent of hospital admissions due to
drug-induced psychosis in 2003-04, according to a study published in
the Australian Medical Journal. John Saunders, Professor of Alcohol
and Drug studies at the University of Queensland, said the latest
research strengthened the need for increased education on the dangers
of cannabis.