son. If one of the cigarettes were made mostly from leaves and the other from flower tops, for instance, they would probably contain different amounts of active chemicals. Growing conditions also affect marijuana's potency, which can vary greatly from region to region and even from season to season in the same place. This variability makes marijuana at best a crude remedy, more akin to herbal supplements such as St. John's wort or ginkgo than to conventional medications.

To date, few herbal supplements have been tested for safety and efficacy in the United States, nor are such products subject to mandatory quality controls. Yet despite these drawbacks, increasing numbers of consumers are using herbal treatments, prompted by their desire for “natural” alternatives to man-made medicines. However, another way to view herbal remedies is to recognize that if they are effective, they contain specific active ingredients. Willow bark contains a pain-relieving compound; marijuana contains cannabinoids such as THC, which lessens nausea. Once identified, chemists can duplicate active compounds in the laboratory. Scientists can also use natural compounds as a basis for creating new medicines. By introducing subtle structural changes in natural molecules, chemists have produced drugs that are more effective and easier to administer and that have fewer side effects than their natural counterparts. So far, a few such analogs or derivatives of cannabinoids are known to exist; others are currently under investigation.

Marijuana used as medicine is not a recreational drug. People who use marijuana solely as a medication do so in order to relieve specific symptoms of AIDS, cancer, multiple sclerosis, and other debilitating conditions. Some do so under the advice or consent of doctors after conventional treatments have failed to help them. In mentioning medical marijuana users, we are referring to people who smoke or eat marijuana exclusively as a treatment for medical symptoms. The fact that many such patients may have prior recreational experience with the drug does not mean that they are using illness as an excuse to get high, although it is possible that some patients might do so. Surveys of marijuana buyers' clubs indicate that most of their members do, in fact, have serious medical conditions.

Medical marijuana users tend to come from different seg-

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