Pubdate: Tue, 09 Oct 2007
Source: Canadian Medical Association Journal (Canada)
Copyright: 2007 Canadian Medical Association
Contact:  http://www.cmaj.ca/
Details: http://www.mapinc.org/media/754
Author: Margret Kopala
Note: Margret Kopala writes columns for the Ottawa Citizen.
Bookmark: http://www.mapinc.org/pot.htm (Cannabis)
Bookmark: http://www.mapinc.org/decrim.htm (Decrim/Legalization)

REEFER MADNESS

Studies have suggested that as many as 1 in 4 cannabis users may be 
genetically at risk for developing schizophrenia or a related 
psychotic disorder. Now, a new study reveals all users are at risk.1

Given recent United Nations' statistics citing Canada as the 
industrial world's leading consumer of cannabis, this news should set 
alarm bells ringing. After all, a leading role in cannabis 
consumption sets the stage for a leading role in psychotic disorders. 
Instead, Canada's mainstream media responded in chorus from The Happy 
Hippy Hymn Book, failing to notice that it is 10 years out of date.

"Legalizing pot makes sense," intoned a National Post editorial 
earlier this summer, while a Globe and Mail article entitled "The 
True North Stoned and Free" giggled about Canada's "little pot habit."

Schizophrenia, a severe form of psychosis, is a brain disorder that 
typically produces delusions, hallucinations, paranoia, disturbances 
in problem solving, memory and concentration, along with depressed 
mood, anxiety and social withdrawal. Its causes are not fully 
understood though environmental stressors (e.g., childhood trauma, 
neglect) are thought to interact with genes to produce disruptions in 
brain chemistry. Longitudinal and other studies demonstrate that 
cannabis, at potencies much greater than 1960s' varieties, is one of 
those stressors and that with their rapidly developing brains, the 
young are particularly vulnerable to developing psychosis later in 
life. The younger the user and the higher the potency of marijuana's 
active ingredient, tetrahydrocannibol, the greater the risk.

In 2005, I interviewed the pre-eminent authority on marijuana and 
psychosis, Professor Robin M. Murray. The Dunedin Birth Cohort Study, 
in which he had participated, and which involved over 1037 
participants from Dunedin, New Zealand, over 3 decades, had just been 
published.2 Murray explained how genes and marijuana could interact 
to increase risk of developing psychosis. The 
catechol-O-methyltransferase (COMT) gene, consisting of a MET 
("normal") type and a VAL ("abnormal") type, metabolizes dopamine, a 
brain chemical that produces the "highs" characteristic of drug and 
alcohol use. A MET/VAL mixture increases risk 2-fold. A VAL/VAL 
mixture increases risk 10 times. A quarter of the population is 
VAL/VAL, he later explained during an interview entitled "Cannabis 
and our genes" with BBC TV's Panorama.

Lead and co-author of countless studies as well as co-editor of 
Marijuana and Madness, Murray is head of the Division of 
Psychological Medicine and professor of psychiatry at King's College 
Institute of Psychiatry in London. He has been a vocal critic of 
British government policy that ignores the mental health issues 
associated with marijuana use. In May, the Institute organized its 
second conference on cannabis and mental health.

According to a recent study, 14% of British patients with 
schizophrenia could have avoided the illness if they had not used 
cannabis.1 This meta-analysis also reveals that while the issue of 
whether cannabis causes psychosis remains unclear, the risk of 
developing psychosis from cannabis use by the general population, 
irrespective of age or genes, is 41%. For heavy users - defined as 
daily or weekly - the risk is in the range of 50% to 200%.

In 2004, the Canadian Addiction Survey found that 22% of all male and 
10% of all female respondents aged 15-24 use cannabis on a weekly or 
daily basis.

However you approach the math, it adds up to a disturbing result.

The news isn't all bad. Canada's marijuana decriminalization bill was 
withdrawn in 2005, and now Health Minister Tony Clement is launching 
an anti-drug campaign. For the medical and other communities, 
however, the work is just beginning. Lobbying governments, informing 
the media, gathering relevant Canadian data and educating families 
are only a small part of what needs to be done. "Experts are now 
agreed on the connection between cannabis and psychosis," Professor 
Murray told USA Today. "What we need now is for 14-year-olds to know it."

Margret Kopala writes columns for the Ottawa Citizen.