Drug Dependence
Drug Dependence, psychological and sometimes physical state characterized by a compulsion to use a drug to experience psychological or physical effects. Drug dependence takes several forms: tolerance, habituation, and addiction. Tolerance , a form of physical dependence, occurs when the body becomes accustomed to a drug and requires ever-increasing amounts of it to achieve the same pharmacological effects. This condition is worsened when certain drugs are used at high doses for long periods (weeks or months), and may lead to more frequent use of the drug. However, when use of the drug is stopped, drug withdrawal may result, which is characterized by nausea, headaches, restlessness, sweating, and difficulty sleeping. The severity of drug withdrawal symptoms varies depending on the drug involved. Habituation , a form of psychological dependence, is characterized by the continued desire for a drug, even after physical dependence is gone. A drug often produces an elated emotional state, an