Drug dependence

The compulsion to continue taking a drug, either to produce the desired effects of taking it, or to prevent the ill-effects that occur when it is not taken. Drug dependence can be psychological or physical. A person is psychologically dependent if he or she experiences craving or emotional distress when the drug is withdrawn. In physical dependence, the body has adapted to the drug, causing the symptoms and signs of withdrawal syndrome when the drug is stopped. Symptoms are relieved if the drug is taken again. Drug dependence develops as a result of regular or excessive drug use, and it develops most frequently with drugs that alter mood or behaviour. Drug dependence may cause physical problems, such as lung and heart disease from smoking and liver disease from excessive alcohol consumption. Mental problems, such as anxiety and depression, are common during withdrawal. Dependence may also be linked with drug tolerance, in which increasingly higher doses of the substance is needed to produce the desired effect. Complications, such as hepatitis or AIDS, contracted as a result of introducing infection into the bloodstream via a dirty needle, may occur. Abusers may suffer from an overdose because of confusion about the dosage or because they take a purer, more potent preparation than they are used to.