Neuroimaging in Drug Addiction

Drug addiction is clinically defined in behavioral terms. The Diagnostic and Statistical Manual-IV of the American Psychiatric Association defines “substance dependence” as a maladaptive pattern of substance use, leading to clinically significant impairment or distress, as manifested by three or more by the following criteria: tolerance, withdrawal, excessive use, inability to cut down, a great deal of time is spent in procuring drug or recovering from its effects, important aspects of the individual’s life are reduced or ignored, and use continues despite ramifications. Examination of the neurobiological underpinnings of drug dependence and the consequences of drug dependence have been a constant focus of research for the past 70 years (in the case of opiate dependence). Initial studies focused on the ability to measure physical dependence on opiate drugs. Once it was determined that withdrawal syndromes could be reliably produced for opiates, alcohol, and other sedative-hypnotic drugs, dependence was often seen in physical terms although a second avenue of research, behavioral pharmacology, also emerged. The field of behavioral pharmacology developed to characterize the effects of drugs of abuse in human subjects and animal species. At this point.. dependence was characterized as being of both physical and psychological natures, reflecting body-mind dualism. One of the global conclusions of the fields of behavioral pharmacology and neuroscience was that selfadministration of drugs was a learned behavior with a biological basis.