redir: Addictive thumb|upright|Heroin bottle The term "addiction" is used in many contexts to describe an obsession, compulsion, or excessive psychological dependence, such as: drug addiction, video game addiction, crime, money, alcoholism, work addiction, compulsive overeating, problem gambling, computer addiction, pornography addiction, etc.

In medical terminology, an addiction is a state in which the body relies on a substance for normal functioning and may occur along with physical dependence, as in drug addiction. When the drug or substance on which someone is dependent is suddenly removed, it will cause withdrawal, a characteristic set of signs and symptoms. Addiction is generally associated with increased drug tolerance. In physiological terms, addiction is not necessarily associated with substance abuse since this form of addiction can result from using medication as prescribed by a doctor. Physical dependence is different from psychological dependence (addiction). The latter is often characterized by a compulsive need for a drug for psychological reasons, while the former is characterized by need for the drug due to tolerance and the need to prevent withdrawal symptoms on discontinuing the use of a drug. Physical dependence however, commonly occurs with both addiction and therapeutic use of drugs.

However, common usage of the term addiction has spread to include psychological dependence. In this context, the term is used in drug addiction and substance abuse problems, but also refers to behaviors that are not generally recognized by the medical community as problems of addiction, such as compulsive overeating.

The term addiction is also sometimes applied to compulsions that are not substance-related, such as problem gambling and computer addiction. In these kinds of common usages, the term addiction is used to describe a recurring compulsion by an individual to engage in some specific activity, despite harmful consequences, as deemed by the user him self to his or hers individual's health, mental state or social life.

Definition

Not all doctors agree on the exact nature of addiction or dependency however the biopsychosocial model is generally accepted in scientific fields as the most comprehensive theorem for addiction. Historically, addiction has been defined with regard solely to psychoactive substances (for example alcohol, tobacco and other drugs) which cross the blood-brain barrier once ingested, temporarily altering the chemical milieu of the brain. However, "studies on phenomenology, family history, and response to treatment suggest that intermittent explosive disorder, kleptomania, pathological gambling, pyromania, and trichotillomania may be related to mood disorders, alcohol and psychoactive substance abuse, and anxiety disorders (especially obsessive–compulsive disorder)." However, such disorders are classified by the American Psychological Association as impulse control disorders and therefore not as addictions.