SCIENTISTS PUSH LINK BETWEEN MARIJUANA AND MENTAL ILLNESS

Eight Studies Show Risk of Schizophrenia Increases From Twofold to Threefold

A pair of articles in the Canadian Journal of Psychiatry has
resurrected the "reefer madness" argument about marijuana and its
links to mental illness.

Cannabis use can trigger schizophrenia in people already vulnerable to
the mental illness -- and this fact should shape marijuana policy,
argue two psychiatric epidemiologists in this month's journal.

The link between marijuana use and schizophrenia is generally accepted
in the psychiatric community. The problem is that the vulnerable
population -- mostly teenagers -- generally isn't eager to absorb the
message.

Australian epidemiologists Louisa Degenhardt and Wayne Hall reviewed
eight international studies of teens and young adults that examined
the link between marijuana use and schizophrenia. They concluded that
using marijuana can precipitate schizophrenia in users who have a
personal or family history of schizophrenia.

One 15-year study of 50,000 young people in Sweden, for example, found
that those who had tried marijuana by the time they were 18 were 2.4
times more likely to receive a diagnosis of schizophrenia. The Swedish
researchers concluded that 13 per cent of schizophrenia cases could be
averted if all cannabis use was prevented.

Another study of almost 5,000 subjects in the Netherlands replicated
the findings, and also found that marijuana users were more likely to
be diagnosed with schizophrenia during the study's three-year followup
period. Other studies suggested that subjects who used marijuana in
their early teens were more likely to be diagnosed with schizophrenia
by their mid-20s.

In a companion article, Hall and Degenhardt argue that the evidence
has policy implications. Young people should be warned of the
marijuana-schizophrenia link -- most schizophrenics are diagnosed by
their late teens, about the same time teens are experimenting with
cannabis.

About one per cent of the population will be diagnosed with
schizophrenia in their lifetimes.

Hall, a researcher at the University of New South Wales in Australia,
said it's a tricky argument to make when, by the numbers, marijuana
will adversely affect so few people. But he points out that
schizophrenia has a high personal and economic cost.

"There are a lot of other reasons to discourage young people from
using cannabis," said Hall.

Wende Wood, a psychiatric pharmacist at the Toronto-based Centre for
Addiction and Mental Health said people who want to smoke marijuana
should wait until they are at least 25. The human brain develops fully
by that time and, if schizophrenia is present, it has usually already
become apparent, Wood says.

The problem is, no one knows how to gauge predisposition to
schizophrenia. The question is how to present the evidence to teens
without falling back on the old "reefer madness" message, which teens
find laughable, said Wood, who frequently speaks to teens about drug
issues. Even the Centre for Addiction and Mental Health has issued a
statement saying that for most people, cannabis doesn't cause harm.

"Kids say 'It's not going to be me.' And with some kids, danger is
part of the appeal," she said.

Alan Young, a criminal law expert at York University's Osgoode Hall
Law School in Toronto, said linking marijuana and mental illness has
been around for decades.

"This is that old hobgoblin that resurfaces now and again. There's
nothing new in the literature. They just keep rehashing the old
literature."