HARVARD MEDICAL REPORT ON MARIJUANA --excerpted from the Harvard Medical School Mental Health Letter, November 1987 Although still illegal, marijuana has become a commonplace part of the American social scene, used regularly by millions and occasionally by millions more. A realistic view of this drug is now more important and easier to achieve. The use of marijuana reached a high point in the late 1970's and early 1980's, and has been declining ever since. In a 1978 survey, 37% of high school seniors said they had smoked marijuana in the last 30 days, and 11% said they used it daily. By 1986 the number who said they had smoked it in the last 30 days had fallen to 23%--lower than in 1975--and the proportion of daily users had dropped steadily to 4%. The trend among people\ aged 18 to 25 is similar. More people over 25 may now be using it occasionally, and young people are still experimenting with it. The main active ingredient of cannabis is delta-9- tetrahydrocannabinol (THC). one of more than 60 related chemicals found in the resin that covers the flowers and top leaves of the cannabis (hemp) plant. Leaves and flowers can be ground up in drinks or food, but are more often dried and smoked in a cigarette or pipe. The pure resin, known as hashish, can also be smoked, eaten or drunk. New breeding and cultivation techniques have raised the THC content of marijuana smoked in the United States as much as 10 times over the last 20 years, from an average of 0.4% to 4%. EFFECTS: The effects last two to four hours when marijuana is smoked, and five to 12 hours when taken by mouth. Although intoxication varies with psychological set and social setting, the most common response is a calm, mildly euphoric state in which time slows and sensitivity to sights, sounds and touch is enhanced. The smoker may feel exhilaration or hilarity and notice a rapid flow of ideas with a reduction in short-term memory. Images sometimes appear before closed eyes;visual perception and body image may undergo subtle changes. It is dangerous to operate complex machinery, including automobiles, under the influence of marijuana. The main physiological effects of cannabis are increased appetite a faster heartbeat, and sightly bloodshot eyes. NEGATIVE REACTIONS: Although the increased heart rate could be a problem for people with cardiovascular disease, dangerous physical reactions to marijuana are almost unknown. No human being is known to have died of an overdose. Like many other drugs, cannabis produces a toxic delirium when taken at very high doses, especially by mouth. The symptoms are confusion, agitation, disorientation, loss of coordination, and often hallucination; the delirium ends when the drug passes out of the body. The most common disturbing reaction to marijuana is acute anxiety, sometimes accompanied by paranoid thoughts, which may lead to panic. The most likely victim of this reaction is an inexperienced user inadvertently taking a high dose in an unpleasant or unfamiliar setting. The best way to handle the anxiety and paranoia is calming support and reassurance. Cannabis is less potent than hallucinogenic or psychedelic drugs and the user is better able to control its effects. LONG TERM EFFECTS: In recent years the psychological and physical effects of long-term use have caused the most concern. Studies are often conflicting and permit various views of marijuana's possible harmfulness. Two recognized signs of addiction are tolerance and withdrawal symptoms. These are rarely a serious problem for marijuana users: almost no one reports an urgent need to increase the dose to recapture the original sensation, and there is little evidence that withdrawal ordinarily presents serious problems to users, or causes them to go on taking the drug. People suffering from drug dependence find that they are constantly thinking about the drug, or intoxicated, or recovering from its effects. The habit impairs their mental and physical health and hurts their work, family life, and friendships. They often know that they are using too much and repeatedly make unsuccessful attempts to cut down or stop. Those problems seem to occur in proportionately fewer marijuana smokers than users of alcohol, tobacco, heroin or cocaine. Most people who develop marijuana dependency would be would be likely to develop other dependencies because of anxiety, depression or feelings of inadequacy. The troubled teen who smokes cannabis throughout the school day certainly has a problem, and excessive use may be one symptom. BEHAVIORAL EFFECTS: Experiments in the U.S. show no effects of fairly heavy marijuana use on learning, perception or motivation over periods as long as a year. In three major studies, conducted in Jamaica, Costa Rica and Greece, researchers compared heavy long-term cannabis users with non-users and found no evidence of intellectual or neurological damage, no changes in personality, and no loss of the will to work or to participate in society. Much attention has also been devoted to the idea that marijuana smoking leads to use of other illicit drugs: the "stepping stone" hypothesis. There is no convincing evidence for or against this. What is clear is that at many times and places marijuana has been used without these drugs, or these drugs have been used without marijuana. REPRODUCTION: Most recent studies on the health hazards of marijuana concerns its long-term effects on the body. Studies have examined the brain, the immune system, the reproductive system, and the lungs. Suggestions of long-term damage come almost exclusively from animal experiments and other laboratory work. Observations of marijuana users and the Caribbean, Greek and other studies reveal little disease or organic pathology associated with the drug. If there were significant damage, we might expect to find a higher rate of these diseases among young people beginning in the 1960's, when marijuana first became popular. There is no evidence of that. The effects of marijuana on the reproductive system are a more complicated issue. In men, a single dose of THC lowers sperm count and the level of testosterone and other hormones. Tolerance to this effect apparently develops; in the Costa Rican study, marijuana smokers and controls had the same testosterone levels. There is no evidence that the changes in sperm count and testosterone affect sexual performance or fertility. In animal experiments, THC has been reported to lower levels of female hormones and disturb the menstrual cycle. When monkeys, rats and mice have been exposed during pregnancy to amounts of THC equivalent to a heavy smoking human's dose, stillbirths and decreased birth weight are sometimes reported in their offspring. There are also reports of low birth weight, prematurity and even a condition resembling the fetal alcohol syndrome in some children of women who smoke marijuana heavily during pregnancy. The significance of these reports is unclear because controls are lacking and other circumstances make is hard to attribute causes. To be safe, pregnant and nursing women should follow the standard conservative recommendation to avoid all drugs, including cannabis, that are not absolutely necessary. LUNGS: A well-confirmed danger of long-term heavy marijuana use is its effects on the lungs. Smoking narrows and inflames air passages and reduces breathing capacity; damage to bronchial cells has been observed in hashish smokers. Possible harmful effects include bronchitis, emphysema and lung cancer. Marijuana smoke contains the same carcinogens as tobacco smoke, usually in somewhat higher concentrations, and is inhaled more deeply and held in the lungs longer, which increases the danger. On the other hand, almost no one smokes 20 marijuana cigarettes a day. Higher THC content in cannabis may reduce the danger of respiratory damage, because less smoke is required for the desired effect. This is only true as long as no significant tolerance develops and users do not try to get proportionately more intense effect from a stronger form of the drug. END