Pubdate: Tue, 02 Mar 2010 Source: Denver Post (CO) Copyright: 2010 The Denver Post Corp Contact: http://www.denverpost.com/ Details: http://www.mapinc.org/media/122 Author: By Nicole Ostrow, Bloomberg News Bookmark: http://www.mapinc.org/pot.htm (Cannabis) STUDY: POT USE BY TEENS LINKED TO PSYCHOSIS Young adults who used marijuana as teens were more likely to develop schizophrenia and psychotic symptoms, including hallucinations and delusions, than those who didn't, an Australian study has found. Those who used the drug for six or more years were twice as likely to develop a psychosis such as schizophrenia or to have delusional disorders than those who never used marijuana, according to research released online by the Archives of General Psychiatry. They were also four times as likely to score high on a list of psychotic-like experiences. The findings build on previous research and show that marijuana use isn't as harmless as some people think, lead study author John McGrath said. The authors said the study was the first to look at sibling pairs to discount genetic or environmental influence and still find marijuana linked to later psychosis. McGrath said his researchers were looking for causes of schizophrenia. The researchers looked at 3,801 young adults. Of the 1,272 participants who had never used marijuana, 26, or 2 percent, were diagnosed with psychosis. Of the 322 who had used marijuana for six or more years, 12, or 3.7 percent, were diagnosed with the illness. The study showed 65 people overall diagnosed with psychosis. Researchers found that those who used marijuana the longest were four times more likely than those who didn't to have the highest scores derived from a list of psychotic-like experiences. Even those who used marijuana for less than three years still had an increased risk of scoring higher than those who had not, McGrath said. - --- MAP posted-by: Jo-D