A growing body of research supports the drug's medical usage, but some of it is cautionary. As Abrams puts it, "you can find anything you want in the medical literature about what marijuana does and doesn't do."
With that in mind, here's an overview of what the research says about the safety and effectiveness of using marijuana to treat various ailments.
Pain: Marijuana has been shown effective against various forms of severe, chronic pain. Some research suggests it helps with migraines, cluster headaches and the pain from fibromyalgia and irritable bowel syndrome because these problems can be triggered by an underlying deficiency in the brain of naturally occurring cannabinoids, ingredients in marijuana. Smoked pot also proved better than placebo cigarettes at relieving nerve pain in HIV patients, according to two recent studies by California researchers.
Marijuana also seems to be effective against nerve pain that is resistant to opiates.
Cancer: The active ingredients in cannabis have been shown to combat pain, nausea and loss of appetite in cancer patients, as well as block tumor growth in lab animals, according to a review article in the journal Nature in October 2003. But there's vigorous debate about whether smoking marijuana increases cancer risk.
Some studies that have looked for a link between cancer risk and marijuana have failed to find one, including a key paper from UCLA published in 2006. "We had hypothesized, based on prior laboratory evidence, including animal studies, that long-term heavy use of marijuana would increase the risk of lung and head and neck cancers," said Hal Morgenstern, a co-author and an epidemiologist at the University of Michigan School of Public Health. "But we didn't get any evidence of that, once we controlled for confounding factors, especially cigarette smoking."
But in California, the first state to legalize marijuana for medical use, in 1996, the Office of Environmental Health Hazard Assessment recently declared pot smoke (though not the plant itself) a carcinogen because it has some of the same harmful substances as tobacco smoke.
The active ingredient in marijuana can increase the risk for Kaposi's sarcoma, a common cancer in HIV/AIDS patients, Harvard researchers reported in the journal Cancer Research in August 2007. And British researchers reported in May in Chemical Research in Toxicology that laboratory experiments showed that pot smoke can damage DNA, suggesting it might cause cancer.
