Many people view drug abuse and addiction as strictly a social problem. Parents, teens, older adults, and other members of the community tend to characterize people who take drugs as morally weak or as having criminal tendencies. They believe that drug abusers and addicts should be able to stop taking drugs if they are willing to change their behavior.

These myths have not only stereotyped those with drug-related problems, but also their families, their communities, and the health care professionals who work with them. Drug abuse and addiction comprise a public health problem that affects many people and has wide-ranging social consequences.

Addiction does begin with drug abuse when an individual makes a conscious choice to use drugs, but addiction is not just "a lot of drug use." Recent scientific research provides overwhelming evidence that not only do drugs interfere with normal brain functioning creating powerful feelings of pleasure, but they also have long-term effects on brain metabolism and activity. At some point, changes occur in the brain that can turn drug abuse into addiction, a chronic, relapsing illness. Those addicted to drugs suffer from a compulsive drug craving and usage and cannot quit by themselves. Treatment is necessary to end this compulsive behavior.

Are you wondering if you have a drug problem? This Drug Abuse Screening Test (DAST-20) can help determine whether you might have a problem with the use or abuse of drugs. It is one of the two standard tests that doctors and counselors use to determine if an individual is an addict.

Use the results to help decide if you need to see a doctor or other mental health professional to further discuss diagnosis and treatment of drug addiction or drug abuse. (This test does NOT measure alcohol use.)

Drug addiction is a pathological or abnormal condition which arises due to frequent drug use. The disorder of addiction involves the progression of acute drug use to the development of drug-seeking behavior, the vulnerability to relapse, and the decreased, slowed ability to respond to naturally rewarding stimuli.

The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) has categorized three stages of addiction: preoccupation/anticipation, binge/intoxication, and withdrawal/negative affect. These stages are characterized, respectively, everywhere by constant cravings and preoccupation with obtaining the substance; using more of the substance than necessary to experience the intoxicating effects; and experiencing tolerance, withdrawal symptoms, and decreased motivation for normal life activities.

It is, both among scientists and other writers, quite usual to allow the concept of drug addiction to include persons who are not drug abusers according to the definition of the American Society of Addiction Medicine. The term drug addiction is then used as a category which may include the same persons who, under the DSM-IV, can be given the diagnosis of substance dependence or substance abuse. (See also DSM-IV Codes)

The terms abuse and addiction have been defined and re-defined over the years. The 1957 World Health Organization (WHO) Expert Committee on Addiction-Producing Drugs defined addiction and habituation as components of drug abuse:
Drug addiction is a state of periodic or chronic intoxication produced by the repeated consumption of a drug (natural or synthetic). Its characteristics include: (i) an overpowering desire or need (compulsion) to continue taking the drug and to obtain it by any means; (ii) a tendency to increase the dose; (iii) a psychic (psychological) and generally a physical dependence on the effects of the drug; and (iv) detrimental effects on the individual and on society.

Drug habituation (habit) is a condition resulting from the repeated consumption of a drug. Its characteristics include (i) a desire (but not a compulsion) to continue taking the drug for the sense of improved well-being which it engenders; (ii) little or no tendency to increase the dose; (iii) some degree of psychic dependence on the effect of the drug, but absence of physical dependence and hence of an abstinence syndrome [withdrawal], and (iv) detrimental effects, if any, primarily on the individual.
In 1964, a new WHO committee found these definitions to be inadequate, and suggested using the blanket term "drug dependence":

The definition of addiction gained some acceptance, but confusion in the use of the terms addiction and habituation and misuse of the former continued. Further, the list of drugs abused increased in number and diversity. These difficulties have become increasingly apparent and various attempts have been made to find a term that could be applied to drug abuse generally. The component in common appears to be dependence, whether psychic or physical or both. Hence, use of the term 'drug dependence', with a modifying phase linking it to a particular drug type in order to differentiate one class of drugs from another, had been given most careful consideration. The Expert Committee recommends substitution of the term 'drug dependence' for the terms 'drug addiction' and 'drug habituation'.

The committee did not clearly define dependence, but did go on to clarify that there was a distinction between physical and psychological ("psychic") dependence. It said that drug abuse was "a state of psychic dependence or physical dependence, or both, on a drug, arising in a person following administration of that drug on a periodic or continued basis." Psychic dependence was defined as a state in which "there is a feeling of satisfaction and psychic drive that requires periodic or continuous administration of the drug to produce pleasure or to avoid discomfort" and all drugs were said to be capable of producing this state:

There is scarcely any agent which can be taken into the body to which some individuals will not get a reaction satisfactory or pleasurable to them, persuading them to continue its use even to the point of abuse — that is, to excessive or persistent use beyond medical need.

The 1957 and 1964 definitions of addiction, dependence and abuse persist to the present day in medical literature. It should be noted that at this time (2006) the Diagnostic Statistical Manual (DSM-IV-TR) now spells out specific criteria for defining abuse and dependence. (DSM-IV-TR) uses the term substance dependence instead of addiction; a maladaptive pattern of substance abuse, leading to clinically significant impairment or distress, as manifested by three (or more) specified criteria, occurring at any time in the same 12-month period. This definition is also applicable on drugs with smaller or nonexistent physical signs of withdrawal, e.g., cannabis.

"Definitions Related to the Use of Opioids for the Treatment of Pain", which defined the following terms:

Addiction is a primary, chronic, neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over drug use, compulsive use, continued use despite harm, and craving.

Physical dependence is a state of adaptation that is manifested by a drug class specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood level of the drug, and/or administration of an antagonist.

Tolerance is the body's physical adaptation to a drug: greater amounts of the drug are required over time to achieve the initial effect as the body "gets used to" and adapts to the intake.

Pseudo addiction is a term which has been used to describe patient behaviors that may occur when pain is undertreated. Patients with unrelieved pain may become focused on obtaining medications, may "clock watch," and may otherwise seem inappropriately "drug seeking." Even such behaviors as illicit drug use and deception can occur in the patient's efforts to obtain relief. Pseudoaddiction can be distinguished from true addiction in that the behaviors resolve when pain is effectively treated