Pubdate: Wed, 21 Jun 2000 Source: Globe and Mail (Canada) Copyright: 2000, The Globe and Mail Company Contact: http://www.globeandmail.ca/ Forum: http://forums.theglobeandmail.com/ Author: Andre Picard SMOKING POT MAY PROMOTE TUMOUR GROWTH, STUDY SAYS Smoking marijuana puts you at greater risk of lung cancer than smoking tobacco, according to a new California study. That's because the same ingredient that makes marijuana smokers high breaks down their body's ability to fight off tumours. In today's edition of the Journal of Immunology, researchers report that tetrahydrocannabinol (THC), the major psychoactive component of marijuana, may even promote the growth of tumours. Steven Dubinett, head of Jonsson Cancer Center at the University of California at Los Angeles, said that experiments on mice demonstrated that THC reduces the body's ability to produce cytokines, powerful immune suppressors that are known to limit tumour growth. Previous research has shown that THC can also lower resistance to both bacterial and viral infections. The principal reason marijuana smoking raises the risk of lung cancer is that marijuana smoke contains a lot more tar than does tobacco smoke. It also contains higher concentrations of carcinogenic hydrocarbons than a regular cigarette. And it also deposits four times as much tar in the respiratory tract than tobacco, according to the research. All told, smoking three marijuana cigarettes is equivalent to smoking a pack of unfiltered cigarettes. "What we already know about marijuana smoke, coupled with our new finding that THC may encourage tumour growth, suggests that regular use of marijuana may increase the risk of respiratory-tract cancer," Dr. Dubinett said. - --- MAP posted-by: greg