When individuals use drugs to such an extent that they have difficulty meeting social and occupational obligations, substance abuse has occurred. Relying on a drug because it makes difficult situations less stressful is called psychological dependency. Developing withdrawal symptoms, such as cramps, is called physiological dependency. When physiological dependence exists, individuals are said to be substance-dependent or addicted. In this text, the term substance abuse is used broadly and includes psychological and/or physiological dependence on a variety of drugs such as alcohol, cocaine, marijuana, sedatives, stimulants, and hallucinogens. Because substance abuse is so widespread, many practitioners of theories have devoted significant attention to this area.