POT LINKED TO PSYCHOSIS

Survey Showing Wide Use Alarms Doc

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

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

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 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 one per cent risk for the general population climbs to nearly 10
per cent if a sibling is schizophrenic.

Fraser Health's six-year-old EPI program has been expanded in recent
years to the rest of the health region.