Update on marijuana.

Marijuana, the illicit drug most widely used by adolescents, is not a benign substance. Inhalation of marijuana smoke is more harmful than tobacco smoke; cannabis smoke delivers 50% to 70% more carcinogens. Other physiological effects include decreased immune function, higher rates of cardiac arrhythmias, and documented cases of cerebellar infarction. Mood and cognitive effects of marijuana include exacerbation of depression and anxiety (including panic attacks), as well as memory problems that may persist for a month after last use. Cannabis abuse is a risk factor for psychosis in genetically predisposed people and may lead to a worse outcome of schizophrenia. The cumulative respiratory, cardiovascular, metabolic, and mental health risks of marijuana are significant and should be emphasized by nurses who work with adolescents.