Substance abuse , also known as drug abuse , is a patterned use of a drug in which the user consumes the substance in amounts or with methods which are harmful to themselves or others, and is a form of substance-related disorder. Widely differing definitions of drug abuse are used in public health, medical and criminal justice contexts. In some cases criminal or anti-social behaviour occurs when the person is under the influence of a drug, and long term personality changes in individuals may occur as well. Drugs most often associated with this term include: alcohol , amphetamines , barbiturates , benzodiazepines , cannabis , cocaine , hallucinogens , methaqualone , and opioids. The exact cause of substance abuse is not clear, with the two predominant theories being: either a genetic disposition which is learned from others, or a habit which if addiction develops, manifests itself as a chronic debilitating disease. Public health practitioners have attempted to look at substance use from a broader perspective than the individual, emphasizing the role of society, culture, and availability. The Health Officers Council of British Columbia — in their policy discussion paper, A Public Health Approach to Drug Control in Canada — has adopted a public health model of psychoactive substance use that challenges the simplistic black-and-white construction of the binary or complementary antonyms "use" vs.