POT USE LINKED TO PSYCHOSIS

A new poll showing 53% of B.C. residents have used marijuana at least
once is disturbing, says a Surrey psychiatrist.

"People should be aware this isn't a benign substance," said Dr. Bill
MacEwan, who addressed a Fraser Health Authority board meeting last Wednesday.

He said clinical evidence from here and around the world increasingly
links pot smoking - especially heavy use at an early age - with psychosis.

"It's a real concern to us that we're seeing these rates of substance
abuse," he said, responding to the poll released last month by B.C.'s
Centre for Addictions Research.

Although crystal methamphetamine is more widely linked to psychosis,
MacEwan said cocaine and marijuana can also stimulate dopamine
receptors in the brain and lead to the mental disorder, often
manifested by paranoia or hallucinations.

"I'm not trying to imply that anyone who smokes marijuana can have
psychosis," he said. "But it's a really interesting figure to see
that more than half of our population is dabbling in drugs that are
having an effect on a system we are looking at in terms of psychosis."

The marijuana link to psychosis is being traced by Fraser Health's
Early Psychosis Intervention program, where at least half of
psychosis patients are substance users and many smoke pot.

"With chronic long-term smokers who are smoking at least one time a
week for longer than a couple of months, we're seeing people have an
increased risk of psychosis," said MacEwan, who is EPI's clinical
director as well as director of psychiatry at UBC.

He estimates the rate of psychosis among those regular pot users is
six to seven times the rate of non-users, who have a roughly one in
100 chance of suffering from psychosis.

"We're finding that people within our program who actually smoke
marijuana and have psychosis, their symptoms are far worse when
they're smoking marijuana," MacEwan said, adding the drug can
interfere with other prescriptions.

"The age of onset of psychosis is lower for those who are substance
abusers," he said.

A significant number of psychiatric patients in this region are
victims of drug-induced psychosis, in addition to people with
schizophrenia or bipolar disorders linked mainly to genetics and
environmental conditions.

One of the other risk factors for psychosis and schizophrenia is life
in a highly urban environment, MacEwan said.

That's why there are heavy clusters of patients in Fraser Health's
EPI program in central Surrey, he said, mirroring a similar cluster
in downtown Vancouver.

Over the last three years, 221 cases were diagnosed in the South
Fraser area, including 138 in Surrey, 39 in Langley, 34 in Delta and
10 in White Rock.

Because the bulk of the risk is genetic, one family member with
schizophrenia automatically means other siblings or children are at a
higher risk.

But MacEwan said that danger has been over-estimated by people,
leading too many to opt, for example, not to have children.

The 1% risk for the general population climbs to nearly 10% if a
sibling is schizophrenic.

Males tend to emerge with mental illness in their late teens and
early 20s, he said, while women are most often diagnosed a decade later.

Fraser Health's six-year-old EPI program is the largest of its kind
in western Canada, and has been expanded in recent years to the rest
of the health region.