Psychopathology in great apes: Concepts, treatment options and possible homologies to human psychiatric disorders

Many captive great apes show gross behavioral abnormalities such as stereotypies, self-mutilation, inappropriate aggression, fear or withdrawal, which impede attempts to integrate these animals in existing or new social groups. These abnormal behaviors resemble symptoms associated with psychiatric disorders in humans such as depression, anxiety disorders, eating disorders, and post-traumatic stress disorder. Due to the outstanding importance of social interaction and the prolonged period of infantile and juvenile dependence, early separation of infants from their mothers and other adverse rearing conditions, solitary housing, and sensory deprivation are among the major albeit non-specific sources of psychopathology in apes. In contrast to the wealth of research in monkeys, psychopathology in apes has been under-studied, and only a few studies have examined how to alleviate abnormal behavior in captive apes. Recent studies have shown that the enrichment of living conditions and behavioral treatment (conditioning) may ameliorate some pathological features, and careful familiarization with novel physical and social environments can help re-socialize behaviorally disturbed animals, but usually not to the extent of successful mating and raising offspring. The possibility of psychopharmacological treatment of the most severe disturbed animal patients has only been reluctantly considered, but a few case reports have revealed encouraging results. This article proposes the need to expand research into ape psychopathology, which would require an essentially interdisciplinary approach of primatology and psychiatry, ultimately to the benefit of both.