HYPERCORTISOLISM ASSOCIATED WITH SOCIAL SUBORDINANCE OR SOCIAL-ISOLATION AMONG WILD BABOONS

Background: The phenomena of basal hypercortisolism and of dexamethaso ne resistance have long intrigued biological psychiatrists, and much i s still unknown as to the causes and consequences cf such adrenocortic al hyperactivity in various neuropsychiatric disorders. We have analyz ed basal cortisol concentrations and adrenocortical responsiveness to dexamethasone in a population of wild baboons living ina national park in Kenya. We tested whether social subordinance in a primate is assoc iated with dexamethasone resistance. Furthermore, we examined whether individual differences in adrenocortical measurements were predicted b y the extent of social affiliation in these animals. Methods: Seventy yellow baboons (Papio cynocephalus) were anesthetized and injected wit h 5 mg of dexamethasone; the cortisol response was monitored for 6 hou rs. The animals were of both sexes in a range of ages and had known ra nks in the dominance hierarchies within their troops. Extensive behavi oral data were available for a subset of ii adult males who were anest hetized under circumstances that also allowed for the determination of basal cortisol concentrations. Results: The socially subordinate babo ons were less responsive to dexamethasone than were the dominant ones; as one manifestation of this, postdexamethasone cortisol values were more than 3 times higher in the dozen lowest-ranking animals compared with the dozen highest. In addition, socially isolated males had eleva ted basal cortisol concentrations and showed a trend toward relative d examethasone resistance. Conclusions: Our findings indicate that socia l status and degree of social affilitation can influence adrenocortica l profiles; specifically, social subordinance or social isolation were associated in our study with hypercortisolism or feedback resistance.