The behavioral neurobiology of self-injurious behavior in rhesus monkeys.

1. Self-injurious behavior (SIB) is prevalent among institutionalized children, but the efficacy of current behavioral and pharmacological treatments is marginal. 2. There is evidence that SIB in humans has a neurobiological basis. A better understanding of the neurobiological factors that may promote or cause SIB is necessary for the development of effective pharmacologic treatments. 3. SIB that is similar in some respects to SIB in humans occurs in nonhuman primates that have been deprived of social experience early in life. An analysis of the "cause" of SIB suggests that it is a relatively straight-forward example of the development of neurobiological and behavioral aspects of aggressive behavior in the absence of social factors that would normally bring the behavior under environmental control. Once induced, however, it becomes environmentally autonomous and its proximal cause is neurobiological in nature. 4. There are three lines of evidence that nonhuman primate SIB is linked to malfunctions in the norepinephrine (NE) and serotonin (5HT) neurotransmitter systems. The activity of these systems appears to be altered by psychosocial deprivation. The functional relationship between the two systems appears to be altered or absent in socially deprived monkeys. Pharmacologic agents that act on these systems alter SIB in monkeys. 5. Preliminary data from socially deprived rhesus monkeys are consistent in major respects with studies linking altered serotonin systems to self-injurious behavior and suicidal motivation in humans who also probably suffer from social deprivation. 6. Taken together, these findings indicate that developmental study of biogenic amine systems, particularly finding ways to circumvent deficits in, or restore functional linkages between, the 5HT and NE systems, will lead to a greater understanding of the neurobiologic basis of SIB in humans and animals and will enable us to develop more effective treatments of SIB.