Psychoneuroimmunology is the study of interactions between behavior, the brain, and the immune system. This article is designed to provide an overview of this new field for the general psychologist. The existence of bidirectional communication pathways between the brain and the immune system and the implications of this network for behavior are emphasized. Implications are that behavioral–psychological processes ought to be capable of altering immune function and that events that occur as part of immune responses should modulate behavior. Evidence for influences in both of these directions is reviewed. The discussion of psychological modulation of immunity focuses on classical conditioning and stress, whereas that of immune modification of behavior highlights behavioral effects produced by substances released by the immune system. Finally, the adaptive role that such changes might play is considered.

The purpose of this article is to provide psychologists with an overview of the new field of psychoneuro-immunology (PNI), which has developed over the past 10 to 15 years. A detailed review is not possible here; various aspects of PNI have recently been given extensive review (Ader & Cohen 1993; Ader, Felten, & Cohen 1991; Cohen & Williamson, 1991; Kemeny, Solomon, Morley, & Bennett, 1993; Plotnikoff, Murgo, Faith, & Wybran, 1991). Neither is the purpose to review our own work in this area. Instead, our goals are to provide (a) a sketch of the basic core facts that led to the coalescence of a new discipline, (b) some indication of the possible functional significance of the basic aspects of organization that have been discovered, (c) a feel for some of the exciting possibilities provided by PNI, and (d) some cautions to note. We will concentrate on the “whys” rather than provide a list of studies. For example, in our discussion of stress and immunity we will not provide extensive documentation that stress can...