Drug dependence includes addiction and habituation. Physicians should attempt to diagnose the underlying conditions that lead to drug taking. These may be classified as social, neurotic, and psychotic. Social drug taking, especially of marihuana, occurs widely today in dissatisfied youths fearful of unfulfillment and rejection, and seeking "identity," status, and pleasure. Its danger is waste and crime, and its treatment largely educational. Neurotic drug taking, like other neurotic symptoms and behavior, occurs as an attempt to relieve anxiety. The danger is addiction, and the treatment psychological. Psychotic drug taking occurs as an attempted escape from severe deepseated intrapsychic misery; a psychosis can also be precipitated by the drug taking. The danger is violence, the treatment medical and psychiatric. There are mixed types.