WILLIAM MERCER MCLEOD FOR TIME GROW IT: Under Proposition 215 in California, police may not seize or destroy this pot plant

Is Pot Good For You?
	Well, no. But the latest research suggests the health risk from occasional use is mild, and it might ease certain ills
	By John Cloud | San Francisco

Posted Sunday, October 27, 2002; 10:31 a.m. EST
I never smoked pot in junior high because I was convinced it would shrivel my incipient manhood. This was the 1980s, and those stark this-is-your-brain-on-drugs ads already had me vaguely worried about memory loss and psychosis. But when other boys said pot might affect our southern regions, I was truly terrified. I didn't smoke a joint for the first time until I was 21.

By 12th grade, about half of young Americans have tried marijuana, which put me in the geeky other half. I used to think this was a good thing, since I never developed a taste for pot and avoided becoming dependent. But as the medical-marijuana movement flowered and weed's p.r. improved, I often wondered if I shouldn't have relished it as a kid, before I had a personal trainer to tsk-tsk my every vice. Shrinking testicles? Mushy brains? I came to see these as grotesqueries invented by antidrug propagandists.

It turns out that the study of marijuana's health effects is at once more complex and less advanced than you might imagine. "Interpretations [of marijuana research] may tell more about [one's] own biases than the data," writes Mitch Earleywine in Understanding Marijuana: A New Look at the Scientific Evidence, published in August by Oxford. For example: "Prohibitionists might mention that THC [delta-9 tetra-hydrocannabinol, the smile-producing chemical in pot] often appears in the blood of people in auto accidents. Yet they might omit the fact that most of these people also drank alcohol. Antiprohibitionists might cite a large study that showed no sign of memory problems in chronic marijuana smokers. Yet they might not mention that the tests were so easy that even a demented person could perform them."

The science of marijuana—especially its potential medical uses—is malleable because it's so young and so contradictory. Although preliminary data are promising, scientists haven't definitively shown that the drug can safely treat nausea or pain or anything, really. Some experts claim the U.S. government has sabotaged medical-marijuana research, and there is evidence to support them. Even so, in the past few years scientists have made rapid advances in their basic understanding of how Cannabis sativa works. By 1993, researchers had found the body's two known receptors for cannabinoids, the psychoactive chemicals in the plant (thc is the main one, but there are at least 65 others). Since then, there has been important new work in several fields that users, potential users and former users should know about—and that voters should take into account before deciding whether to legalize pot.

So much new research has appeared that in November the Journal of Clinical Pharmacology and the National Institute on Drug Abuse will publish a 100-page supplement devoted entirely to marijuana. The Journal gave Time an advance look; it's a comprehensive review that will annoy both sides in the drug war. You won't find clear evidence that pot is good or evil, but the research sheds light on some of the most important questions surrounding the drug:

Can it kill you?

No one has ever died of THC poisoning, mostly because a 160-lb. person would have to smoke roughly 900 joints in a sitting to reach a lethal dose. (No doubt some have tried.) But that doesn't mean pot can't contribute to serious health problems and even death—both indirectly (driving while stoned, for instance) and directly (by affecting circulation, for example). A paper published last year in the journal Angiology found 10 odd cases in France of heavy herbe smokers who developed ischemia (an insufficient blood supply) in their limbs, leading in four cases to amputations. It's not clear that marijuana caused the decreased blood flow, but the vascular problems did worsen during periods of heavy use. Another 2001 paper, in Circulation, found a nearly fivefold increase in the risk for heart attack in the first hour after smoking marijuana—though statistically that means smoking pot is about as dangerous for a fit person as exercise.

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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