spite exposure to a statewide advertising campaign in favor of medical marijuana, teens in California were actually an exception to the national trend: their perception of marijuana's harmfulness did not decrease between 1996 and 1997. Thus, there is no evidence that the medical marijuana debate has altered adolescents' perceptions of the risks of using marijuana.37

WEIGHING MARIJUANA'S HARMS

For most people the main adverse effect of acute marijuana use—that is, the immediate effect of a single potent dose—is diminished psychomotor performance. A few people also experience bad feelings that range from uneasiness to profound emotional discomfort. Marijuana and marijuana-based drugs pose a greater danger to people at risk for psychiatric disorders, especially those who are vulnerable to substance dependence. This spectrum of risk for acute side effects lies well within tolerable limits for prescription medications.

An even more important concern about medical marijuana is the drug 's chronic side effects (those that crop up during extended use). These effects fall into two categories: the long-term consequences of smoking and the risks of chronic exposure to THC. Marijuana smoke, like tobacco smoke, is associated with increased risk of cancer, lung damage, and poor pregnancy outcomes. Smoked marijuana is thus unlikely to prove to be a safe medication for any chronic medical condition.

A less prevalent side effect of protracted marijuana use is dependence, which tends to occur only in a vulnerable subpopulation of users, most notably adolescents with conduct disorder. As one might expect, people with psychiatric problems and those vulnerable to substance abuse may be at risk of becoming dependent on medical marijuana.

In addition to the dangers of smoke inhalation, another drawback of using marijuana cigarettes as a drug delivery system is their highly variable composition. Plants grown under different conditions contain variable mixtures of cannabinoids, and their dried leaves may also be contaminated with toxic bacteria and fungus.

As for the notion that the sanctioning of medical marijuana



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement