Is Pot Good For You?

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Does it make you sick?
Marijuana may directly affect the immune system, since one of the body's two known receptors for cannabinoids is located in immune cells. But the nature of the effect is unclear. A recent study showed that THC inhibits production of immune-stimulating substances. But cigarette smokers may do greater harm to their immunity than pot users, who tend to smoke less. A study published earlier this year found that tobacco smokers but not marijuana smokers had high levels of a type of enzyme believed to inflame the lungs. Dr. Donald Abrams, professor of clinical medicine at the University of California, San Francisco, found that short-term cannabis use doesn't substantially raise viral loads of HIV patients. (People with HIV sometimes smoke marijuana to stimulate appetite.) In fact, his study participants who smoked pot enjoyed significantly higher increases in their lymphocytes (cells that help fight disease) than those who took a placebo.

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Can it give you cancer?
Data on cancer also generate mixed conclusions. A 1999 study of 173 patients with head and neck cancers found that pot smoking elevated the risk of such cancers. (Smokers of anything should also worry about lung cancer.) But it's not clear that THC is carcinogenic. The latest research suggests that THC may have a dual effect, promoting tumors by increasing free radicals and simultaneously protecting against tumors by playing a beneficial role in a process known as programmed cell DEAth.

Is it addictive?
Those who believe you can't become physically or psychologically dependent on marijuana are wrong. At least three recent studies have demonstrated that heavy pot smokers who quit can experience such withdrawal symptoms as anxiety, difficulty sleeping and stomach pain. On the other hand, the risk of becoming dependent on marijuana is comparatively low. Just 9% of those who have used the drug develop dependence. By comparison, 15% of drinkers become dependent on alcohol, 23% of heroin users get hooked, and a third of tobacco smokers become slaves to cigarettes.

Does it make you stupid?
Potheads are dumber than nonusers, but only a little. Earlier this year, the Journal of the American Medical Association published a study of 102 near-daily marijuana users who wanted to quit. The authors found that the longer subjects had toked up, the worse their memories and attention spans. But they were hardly like Gobi, the Saturday Night Live wastoid who is so ruined he can barely talk. Participants who had used cannabis regularly for an average of 10 years fared significantly worse on only two of 40 indices of cognitive functioning (they had particular trouble estimating how much time had passed during a test). Those stout folks who had been smoking pot for an average of 24 years did significantly worse on 14 of the tests. But scientists can't say that marijuana causes such problems. "These long-term users may have been worse off in the first place, before they ever smoked marijuana," says Dr. Harrison Pope, a Harvard psychiatrist who wrote an editorial accompanying the study arguing that "we must live with uncertainty" on whether pot causes long-term cognitive impairments.

What about sex?
The latest studies suggest I needn't have fretted so much about pot's gonadal consequences. "Marijuana might interfere with [kids'] ability to go through puberty," says Dr. Adrian Dobs, co-author of a paper on the endocrine effects of the drug in the upcoming Journal of Clinical Pharmacology. "But the abnormalities seen are not really clinically significant." Despite tales of male potheads growing breasts, the long-term effects on adult glands are uncertain.

Do the sick really benefit?
So if marijuana can be harmful to healthy people--but usually isn't--could it actually be good for the sick? This is where the science gets scraggier--and in the absence of data, politics takes over. What we know is that healers have accumulated copious anecdotes on weed's powers over the past 4,700 years. Understanding Marijuana author Earleywine credits a (possibly mythical) Chinese emperor with introducing the plant as a treatment for gout around 2700 B.C. But the emperor also thought his pot potion would help memory, making him the first of many fans to aggrandize the drug's medical potential. The ancient Greek doc Galen even used the drug to treat flatulence.

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