Medical uses for the drug, of course, are really what have legitimized the drug in the eyes of many politicians and voters. Cannabis is an annual that literally grows like a weed in many parts of the world. The drug contains more than 60 chemicals, called cannabinoids (THC being the most important), that have a number of medicinal benefits -- including reducing nausea from cancer chemotherapy, easing pain from multiple sclerosis, and lessening pressure behind the eyes in glaucoma patients. As well as being a minor intoxicant, THC can work as a muscle relaxer and antidepressant, and stimulate the appetite. For these reasons, marijuana is also used for even more minor conditions. In California, for example, patients can walk off with a pot prescription for insomnia or attention deficit disorder.