AbstractAccording to our proposal the endogenous opioid functions, activated mainly by social interactions in early childhood and by stress later in life, serve multiple roles both in early ontogenesis and in adulthood. First, they might insure social cohesion. Second, they can mediate a special kind of homeostatic regulation, and third, they seem to determine characteristic cognitive functions: primary process thinking, primitive forms of defense mechanisms and basic conceptual structures guiding prosocial behavior. We propose that an alternation of two biological states, one with and one without the involvement of the endogenous opioid mechanisms, characterizes the normal course of life. These two states are supposed to represent different forms of homeostatic regulation and different kinds of cognition. Physical and psychological health seems to be dependent on the relative part each takes in the life of an individual. On the basis of some considerations discussed in this paper the endogenous opioid functions seem to be relevant factors of human cognition. The conceptual scheme of psychoanalysis, worked out on the basis of empirical data, could be Led to describe the cognitive characteristics which, in our proposal, were suggested to ensue on the endogenous opioid activity.