Pubdate: Wed, 21 Jun 2000
Source: Globe and Mail (Canada)
Copyright: 2000, The Globe and Mail Company
Author: Andre Picard


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.
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