Addictions: what does biology have to tell?

Abstract

The changes in the nervous system induced by the repeated use of dependence-producing drugs are not limited to those associated with tolerance and physical dependence (withdrawal syndromes). They also involve memory traces that link both positive and negative reinforcing effects of drugs to affective states and environmental stimuli. Long after the obvious signs of withdrawal have abated, these affective states and stimuli may evoke urges to use the drug again (craving), some component of withdrawal distress, or both. In those who were formerly drug dependent, ingestion of a drug that produces a positive reinforcement may have a ‘priming’ effect resulting in increased craving for the drug of dependence. In addition to traditional pharmacological approaches, which seek to reduce relapse by ameliorating changes associated with withdrawal, or to block the reinforcing actions of drugs, newer approaches to relapse-prevention teach former users how to avoid situations that evoke craving or to cope with it when it cannot be avoided. In clinical practice, the distinction between positive and negative reinforcement is not always clear. Evidence that drug use alters the biology of the organism does not necessarily assume that society will attribute continued drug-taking to a ‘disease’ rather than to wilful misconduct.