And that seemingly benign plant of yesteryear can, in fact, be addictive: Fifteen percent of people entering a drug-abuse program reported marijuana as their primary drug of abuse in a 2002 survey. To be sure, people who abuse drugs of any kind quite often have some other psychiatric problem, such as depression or anxiety. There is some evidence, Volkow says, that people with mental disorders are more likely to become dependent on marijuana because the drug at first provides relief by boosting mood, thus conditioning the person to seek it repeatedly. Animal research also suggests that a chronically stressful environment may increase vulnerability to dependence, which could be relevant in kids exposed to chronic social stressors, she says.
Smoking pot bought on the street is quite a different matter than using marijuana medically to ease pain and nausea, experts argue. Indeed, in February, the American College of Physicians called for easing the ban on medical marijuana and increasing research into therapeutic effects of cannabanoid-based medications taken orally or vaporized and inhaled to avoid the harsh combustion of smoking. "When people are in pain, you don't tell them to smoke opium, you [prescribe] morphine," says Steven Childers, professor of physiology and pharmacology at Wake Forest University and a panel member on the oft-cited 1999 Institute of Medicine report, Marijuana and Medicine: Assessing the Science Base. Studies have suggested marijuana is beneficial in reducing intra-ocular pressure in glaucoma patients and those with neuropathic pain—associated with diabetes or amputation—that doesn't respond well to opioids or antidepressants. Marinol is a THC-based drug approved in the United States to battle weight loss in AIDS patients and nausea in cancer patients undergoing chemotherapy. The makers of Sativex, an oral spray approved in Canada for pain associated with multiple sclerosis and for cancer patients, are seeking approval in the United States. And medical uses, says Childers, could be of great benefit as the baby boomers grow old.