There's good news for moderate smokers in the latest research on marijuana and bad news for heavy smokers. Getting caught or causing an accident while stoned are still the greatest dangers, but those who smoke marijuana on a weekly or daily basis over several years risk potentially serious damage to some mental faculties and to their lungs. Adolescents who are heavy pot smokers may retard their emotional and intellectual development.
How Does Pot Work?
Pot creates a high by affecting strategic locations in the brain, including the hippocampus, where linear thinking takes place; the rostral ventrome-dial medulla, at the base of the brain, which modulates the intensity of pain sensations; and the cerebellum, which coordinates movement and balance. Until recently, no one understood how marijuana penetrates the brain.
Then, in 1992, a Hebrew University team discovered chemicals in the brain that are similar to cannabinoids, the class of chemicals contained in marijuana. These newly discovered chemicals, called anandamides, may block pain and help regulate sleep patterns. THC (delta-9-tetrahydrocannabinol), the marijuana ingredient most responsible for altering consciousness, uses the same docking station in brain cells as anandamides do. Pot defender Dr. John P. Morgan, co-author of Marijuana Myths, Marijuana Facts, says that THC merely ''borrows a prepared pathway''; that is, it makes use of a functioning system without contaminating it. Pot foe Dr. Robert DuPont, former head of the National Institute on Drug Abuse, says that THC ''pirates'' the brain's communication network. By that, DuPont means that pot users are allowing THC to steal cell receptors that should be used only by the brain's chemicals and are risking permanent changes to the brain.
Does Pot Make You Stupid?
Repeated studies of long-term, heavy pot smokers in Costa Rica have yielded no convincing evidence that smokers are slower thinkers than nonsmokers. And Dr. Andrew Weil, author of the first double-blind human experiments with marijuana, in 1968, contends that ''whatever changes may occur in mental function associated with marijuana use, they will all reverse if you get people away from it.'' However, studies in India, Europe and the U.S. have found that heavy use brings an increased risk of potentially permanent short-term-memory loss and may hinder the ability to adapt to new rules and situations.
While the question of whether or not pot inflicts permanent damage remains unresolved, scientists agree that pot has temporary cognitive effects. In a recent study, researchers at McLean Hospital, in Belmont, Massachusetts, found that mental function in heavy users was inhibited for twenty-four hours after subjects had smoked pot, long after the high was gone. If you smoke pot regularly and don't notice any problems, then you may not be suffering any damage at all — or you may have adjusted to a lower intellectual standard.
Can Pot Hook You?
Marijuana has been ranked with caffeine in addictiveness potential — considerably lower than alcohol, nicotine or cocaine. About one in every eleven people who try pot becomes a chronic, heavy user for a time. Most seem able to stop at will. Those who do become dependent on marijuana sometimes undergo a form of withdrawal when they abstain. A credible study by psychiatrists at the University of California at San Diego documented withdrawal symptoms in about sixteen percent of their study subjects, who had all used pot daily for an average of almost seventy months. These symptoms included nervousness, tension, restlessness, sleep disturbance and appetite changes.
''Smoking pot every third Saturday night isn't going to damage you in any measurable way, unless you do something stupid when you're stoned,'' says Mark Kleiman, a drug policy expert at the University of California at Los Angeles. The hidden risk is that ''you won't be able to keep it to every third Saturday night.''
Does Pot Hurt Your Lungs?
Marijuana smoke contains many of the same toxic chemicals as tobacco smoke, including carcinogens such as tar, carbon monoxide and cyanide. Occasional pot users do not generally inhale enough smoke to affect the linings of the trachea and bronchial tubes. Heavy users, however, often experience the respiratory problems that pack-a-day cigarette smokers do, such as chronic bronchitis and exacerbation of asthma.
The largest cohort of people using pot on a regular, long-term basis in the U.S. began smoking in the Sixties, so they haven't yet reached the age when cancers manifest with a vengeance. Small-scale studies of chronic pot users' lungs have revealed abnormal changes in bronchial cells, indicating an increased risk of cancer, and many scientists believe that pot's lung-cancer risk could prove to be comparable to that of cigarettes.
Does Pot Affect Fertility?
Long-term use of marijuana may lower sperm counts in men and may interfere with menstrual cycles in women. According to Buzzed, a comprehensive guide to alcohol and illicit drugs produced by the Duke University Medical Center, pot ''suppresses the production of hormones that help to regulate the reproductive system.'' The scientific literature does not give a clear message that these disruptions are severe enough to affect fertility. Pregnant women, however, should avoid marijuana: There is some evidence that babies born to pot smokers may have a reduced birth weight or worse. According to November's Lancet article by Wayne Hall and Nadia Solowij, ''Infants exposed in utero to cannabis [may] show behavioral and developmental effects during the first few months after birth. Between the ages of four and nine years, exposed children have showed deficits in sustained attention, memory and higher cognitive functioning.''
Can Pot Cure A Headache?
''In the 1970s and 1980s, drug companies such as Eli Lilly were very excited about the medical uses of marijuana,'' says Dr. John Morgan, ''before the War on Drugs escalated and they gave up.'' One of the exciting discoveries in pot research — most of which is being conducted in Europe — is that cannabinoids probably have pain-killing properties; there are some reports that they could be useful in alleviating migraines. They also may work as antioxidants, thus reducing brain swelling in stroke and head-trauma victims. Pot is now used regularly — often illegally — to reduce the need for morphine, to counteract nausea and to stimulate appetite in people with wasting diseases like AIDS.