Drug Addiction

Drug Addiction as a

Psychobiological Process

The emphasis is on biological mechanisms underlying addiction, although some other factors influencing drug addiction will also be discussed. The presentation is limited primarily to psychomotor stimulants (e.g., amphetamine, cocaine) and opiates (e.g., heroin, morphine) for two reasons. First, considerable knowledge has been gained during the past 15 years regarding the neurobiological mechanisms mediating their addictive properties. Second, these two pharmacological classes represent the best examples of potent addictive drugs, and the elucidation of their addiction potential can provide a framework for understanding abuse and addiction to other psychotropic agents.

Some psychologists and sociologists assert that animal studies do not model the important psychological variables governing drug addiction. They suggest that psychological processes critical in the etiology of addiction cannot be studied in animal models and/or that environmental influences important in producing an addiction cannot be duplicated in animal studies. This position is generally untenable, and animal models have been developed that accurately represent the primary processes involved in drug addiction. Support for the validity of these animal models will emanate from an understanding of the characteristics and the neural basis of drug addiction summarized in the following sections.

The arguments presented in the chapter are tenable, but they represent only one of several perspectives used in studying addiction. The terminology and even some aspects of the empirical data are the topics of scientific debate. The objective of this chapter is not to provide a balanced presentation of controversial issues, but rather to develop a unifying framework for understanding the psychobiological basis of addiction.

Concept of Addiction

Before proceeding with an examination of the mechanisms underlying drug addiction, it is necessary to define the term addiction and to examine the main characteristics of drug addiction. Delineation of the salient attributes of addiction helps to establish the criteria that must be fulfilled in a valid animal model and helps to determine what biological processes are relevant to the etiology of addiction.

Issue of Terminology

Drug addiction refers to a situation where drug procurement and administration appear to govern the organism’s behavior, and where the drug seems to dominate the organism’s motivational hierarchy. Jaffe (1975) has described addiction as "a behavioral pattern of compulsive drug use, characterized by overwhelming involvement with the