The Consensus panel at the National Institutes of Health defines opioid dependence as a cluster of cognitive, behavioral, and physiological symptoms in which an individual continues to use opiates despite significant physiological and psychological harm caused by the ingestion of the drugs. The condition is characterized by the patient's repeated self-administration of an opiate drug over an extended period of time resulting in the development of opioid tolerance, compulsive drug taking behavior, and withdrawal symptoms upon cessation of use. Patients may develop a dependence on opioids with or without symptoms of physiological tolerance and withdrawal; these patients usually have a long history of opioid self-administration either through intravenous drug injection, intranasal ingestion or smoking.
Health care providers in the United States agree that although the factors that contribute to opiate dependency are poorly understood, one thing is certain: once physical dependence on opiates develops, it can constitute a medical disorder that requires treatment intervention. Methadone maintenance treatment in conjunction with medical attention and psychiatric counseling can do a great deal to alter the course of the natural history of opiate dependence and help prolong periods of abstinence from illicit drug use in addicted patients.
Decades of clinical research on the neurobiology and pathology of opiate dependence have revealed that individual vulnerability to drug abuse is partially inherited and the pattern and degree of severity of this disorder are strongly influenced by environmental factors. This conclusion is supported by evidence gathered in government-funded family, twin, and adoption studies that indicate that the children of opiate dependent parents have a higher predisposition and susceptibility to abuse and dependence after their initial use of opioids compared with children whose parents do not use drugs. Neurobiological studies suggest that there are a number of opioid receptor pathways in the human cerebral cortex that play an important role in the development of drug dependence and the intensity of symptoms of physical withdrawal experienced by opiate addicted patients.
Abstract - Effective Medical Treatment of Opiate Addiction, National Institute of Health Consensus Statement 1997