Pubdate: Wed, 08 Nov 2006 Source: Tri-City News (Port Coquitlam, CN BC) Copyright: 2006 Tri-City News Contact: http://www.tricitynews.com/ Details: http://www.mapinc.org/media/1239 Author: Jeff Nagel 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. - --- MAP posted-by: Elaine