point in their lives. By comparison, nearly 14 percent of adults met the criteria for dependence on alcohol and 36 percent met the criteria for tobacco dependence.

Clearly, marijuana use carries a risk of dependence and abuse—a danger that must be taken into account if either the crude plant extract or its active ingredients are to be used for medical purposes. For certain patients—particularly adolescents, people with psychological or social problems, and those with an inherited predisposition to substance abuse—marijuana-based medications may not be worth the risk. On the other hand, compared with alcohol, tobacco, and several prescription medications, marijuana's abuse potential appears relatively small and certainly within manageable limits for patients under the care of a physician.

PSYCHOLOGICAL HARMS

Compared with the physical dangers of marijuana use, its psychological drawbacks are far less well understood. Indeed, some of the psychoactive effects of marijuana—such as anxiety reduction, sedation, and euphoria —can be counted among the drug's potential benefits for certain patients. This paradox, plus the fact that the vast majority of research on the psychological effects of marijuana and cannabinoids concerns intoxication and recreational use, makes it difficult to anticipate the psychological impact of medical marijuana use.

One would expect that people who use marijuana solely as a medicine have very different mental experiences than those of recreational users simply because the circumstances under which people use psychoactive drugs strongly influence their psychological reactions. Most of the existing psychological research on marijuana was conducted on people who had previously used the drug, so very little is known about its potential to cause adverse psychological reactions in first-time or inexperienced users. Moreover, the majority of psychological studies have measured the effects of a single, often large, dose of the drug, rather than the chronic exposure that would be more typical of medical use. Instead, it is the subtler effects of low doses of marijuana and cannabinoids that must be taken into account if they are to be used as



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