Opioid dependence is a medical diagnosis characterized by an individual's inability to stop using opioids such as morphine, heroin, codeine, oxycodone, hydrocodone, or hydromorphone, even when it is in his or her best interest to quit. In 1964 the WHO Expert Committee on Drug Dependence introduced "dependence" as "A cluster of physiological, behavioural and cognitive phenomena of variable intensity, in which the use of a psychoactive drug takes on a high priority. The addict develops a preoccupation with a desire to obtain and take the drug and persistent drug-seeking behavior. Problematic consequences of drug dependence may be biological, psychological or social, and usually interact.
Defining characteristics of drug dependence include a strong desire or a sense of compulsion to take the drug. Difficulties in controlling drug-taking behavior at its onset, termination, or levels of use. A physiological withdrawal state when drug use is stopped or reduced, as evidenced by the characteristic withdrawal syndrome for the substance or use of the same or similar substance with the intention of relieving or avoiding withdrawal symptoms. Evidence of tolerance, such that increased doses of the drug are required in order to achieve effects originally produced by lower doses. Progressive neglect of alternative pleasures or interests because of drug use, increased amount of time necessary to obtain or take the drug or to recover from its effects. Persisting with drug use despite clear evidence of harmful consequences, such as damage to the liver, depression, impairment of cognitive functioning or relationship problems.
Typically, opioid-dependent addicts suffer from at least one severe psychiatric comorbidity as a result of traumatic events in their lives. Opioids are known to have strong antidepressive, anxiolytic and antipsychotic effects. It is not uncommon for people who suffer from anxiety or depression due to traumatic events such as abuse or abandonment, to try to self-medicate by taking opioids. Opioids are excellent pain medication, but it is their ability to produce euphoria that makes them attractive to addicts.