Another Sort of Smoke

Marijuana: "justifies serious national concern

More than 25 million Americans spent some $24 billion in 1980 for the illegal privilege of regularly smoking marijuana. Another 25 million have tried the drug at least once, making it the most widely used illegal substance in the country. A major reason: the tenacious belief among marijuana smokers that the occasional joint does little, if any, harm. Last week the Institute of Medicine of the National Academy of Sciences issued a long-awaited, 188-page report on the effects of marijuana. Its main finding: widespread use of the drug "justifies serious national concern." But after 15 months of study, the academy concluded that there is, as yet, insufficient research to decide whether or not marijuana causes irreversible long-term health damage. The 22-member study committee, chaired by Arnold Relman, editor of the New England Journal of Medicine, analyzed 1,000 scientific studies of the health effects associated with marijuana and called for further research. Among its conclusions:

Behavioral Effects. The principal active element in marijuana, delta-9-tetrahydrocannabinol (THC), like alcohol, impairs motor coordination, the ability to follow a moving object and to detect a flash of light. Since these functions are necessary for safe driving, the report notes, their impairment "may suggest a substantial risk." The effects may last four to eight hours after the time the user feels a "high," unlike alcohol, which is more quickly metabolized. Marijuana hampers short-term memory, slows learning and produces distortions of judgment, including reactions of panic and confusion. Consequently, there is special concern since much of the heavy use of marijuana "takes place within the school setting." Says Charles O'Brien, a professor of psychiatry at the University of Pennsylvania School of Medicine and a member of the committee: "There's no way a student's brain can function normally when he uses marijuana daily. It's a definite risk, but there's no way to evaluate that risk in a quantitative way." Mild withdrawal symptoms that sometimes occur among heavy users indicate the drug can lead to physical dependence, but the committee stressed that so far there is no evidence that marijuana actually causes addiction.

Heart and Lung Damage. Like heavy cigarette smoking, chronic heavy marijuana use may lead to cancer of the respiratory tract and seriously impair the lungs. It can raise the heart rate and blood pressure, as does stress. Such effects are serious for people who suffer from hypertension, cerebrovascular disease and coronary atherosclerosis (fatty deposits in the blood vessels of the heart).

Impairment of Reproductive and Immune Systems. Regular marijuana use cuts down on the number and activity of sperm, but there is no proof of resulting loss of fertility. Studies on animals have shown a decrease in ovulation and female reproductive hormone levels. Marijuana is known to pass through the placenta, but the committee found "no evidence yet" of birth defects in human fetuses. Nor is there conclusive evidence that marijuana causes any chromosome damage or suppresses the body's ability to protect itself against infection.

The report emphasized the need for more detailed long-term study because marijuana is widely used, and its components remain in the body for long periods, accumulating at levels that may be far higher than the levels after a single dose. The study urged further research into ways THC and other marijuana derivatives can be of greater use in treating glaucoma, asthma and the nausea and vomiting associated with chemotherapy in cancer patients. The aim: to find ways of increasing the medically beneficial uses of marijuana while diminishing its potentially harmful effects.

Medical science's uncertainty about the serious risks of marijuana has apparently been noted by at least one segment of the population. Also released last week was a University of Michigan study that revealed regular marijuana use among 17,000 high school seniors across the country has dropped from a high of 11% in 1978 to 7% last year. The most frequently cited reason: the teenagers' concern about possible adverse effects of marijuana smoking on physical and psychological health. sb

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