Pubdate: Fri, 03 Apr 2009 Source: Chilliwack Progress (CN BC) Copyright: 2009 The Chilliwack Progress Contact: http://www.theprogress.com/ Details: http://www.mapinc.org/media/562 Author: Kim Dawson Note: Dr. Kim Dawson is a psychologist in the Child and Youth Mental Health program as part of the Ministry of Children and Family Development, Government of BC. Bookmark: http://www.mapinc.org/find?252 (Cannabis - Psychosis) REALITY CHECK : DOES CANNABIS CAUSE PSYCHOSIS? Psychosis is a class of mental illnesses characterized by strongly-held irrational beliefs not consistent with reality (delusions) and bizarre sensations of objects or people that are not actually present (hallucinations). Leading up to a psychotic episode is often a period including lack of motivation, lack of emotions, and difficulty thinking or speaking in a way that makes sense to others or oneself. As a drug in the class of psychedelic substances, cannabis can, within minutes after inhaling its vapors, induce psychosis-like symptoms including hallucinations, paranoid delusions, lack of motivation, and difficulty thinking or speaking logically. So, can cannabis cause psychosis? According to the BC Schizophrenia Society, the answer to the question of whether cannabis causes psychosis is yes. This is based on many research studies from around the world which have found that the rates of cannabis use are about twice as high among people with schizophrenia as among the general population. In addition, surveys of patients with psychotic illnesses have found that 20 to 40 per cent report lifetime cannabis use. But these elevated rates of association between cannabis use and psychotic illness do not resolve the question of whether cannabis use is a consequence or a cause of psychosis. A very large Swedish study (which had over 45,000 subjects) showed that even when other illnesses that overlap with psychosis were controlled for, self-reported heavy cannabis users (those who used more than 50 times) were two times more likely than non-users to have been diagnosed with schizophrenia 15 years later. In a large Netherlands study (having over 4,000 subjects), individuals with psychotic symptoms who used cannabis were nearly three times more likely than non-users to manifest psychotic symptoms between one and three years later. In these studies, the association between cannabis and schizophrenia held even after adjusting for the use of other drugs. If you read the fact sheet available on the BC Schizophrenia Society's website ( www.bcss.org/2006/01/resources/family-friends/cannabis-and-psychosis), you will find that recent research is mounting that when someone uses marijuana in their teens, uses heavily, and is vulnerable to psychosis, marijuana can trigger early onset of psychotic illnesses. Moreover, of persons with psychotic illness who don't respond to treatment, 70 per cent or more are using cannabis or other drugs (including nicotine, alcohol, and heroin). But who are these vulnerable people? How does a person become vulnerable to psychosis? A person who is vulnerable to psychosis shows symptoms of psychosis. This might sound like circular logic. But it is important to realize that psychosis isn't a single mental disorder, it's a spectrum. This spectrum ranges from a brief psychotic episode lasting for a few minutes (which can be induced by cannabis and some other drugs), all the way to full-blown schizophrenia which can last for years. The findings that heavy marijuana use (50 times a year or more) can predispose groups of vulnerable individuals to schizophrenia years later are worth a closer look. Clearly, not all adults with schizophrenia used cannabis in adolescence and this does put to rest the idea that cannabis causes schizophrenia. In addition, the majority of teenaged cannabis users don't go on to develop schizophrenia in adulthood, so we can't conclude that cannabis use is the only cause. But, in combination with other factors, cannabis may have a significant influence on later development of schizophrenia, especially if there were already psychotic symptoms when cannabis use began. In conclusion, it is important to realize that we cannot eliminate cannabis use totally from the population, nor would we want to. Marijuana has legitimate uses as a medication for pain management in multiple sclerosis, arthritis, and other illnesses (see Health Canada's website at www.hc-sc.gc.ca/dhp-mps/marihuana/index-eng.php ). Instead, it may be advisable to screen young people for symptoms of psychosis and then focus on reducing cannabis use in vulnerable youth. To engage youth who commonly use drugs, this would mean designing educational approaches that are informative rather using scare tactics. One recommended approach would be to engage young people in an open-minded and balanced discussion of both psychotic symptoms and drug use. Dr. Kim Dawson is a psychologist in the Child and Youth Mental Health program as part of the Ministry of Children and Family Development, Government of BC. - --- MAP posted-by: Larry Seguin