Drug and alcohol use have historically been common among military personnel. Drugs have been used by soldiers to reduce pain, lessen fatigue, and increase alertness, or to help them cope with boredom or panic that accompany battle. During the U.S. Civil War, medical use of opium resulted in addiction among some soldiers. In the modern U.S. military, drug use became a recognized problem during the Vietnam War in the late 1960s and early 70s. Approximately 20 percent of Vietnam War veterans reported having used narcotics (e.g., heroin, opium) on a weekly basis, and 20 percent also were considered to be addicted based on reported symptoms of dependence (Robins, Helzer, & Davis, 1975). Although few personnel continued using heroin when they returned home, there were concerns about addiction.

Similar to drug use, heavy drinking...