TOWARDS A SOCIOBIOLOGICAL MODEL OF DEPRESSION - A MARSUPIAL MODEL (PETAURUS BREVICEPS)

Background. This is a sociobiological approach to depression using hierarchy and its hypothesised relevance to self-esteem in the marsupial sugar glider (Petaurus breviceps). Method. Differential access to resources between the dominant and submissive animal is measured by observation in four stable colonies. The dominant animals from two of these colonies are then introduced into the other two, resulting in the transferred former dominants becoming subordinate. Behavioural and biochemical measures relevant to depression and involving access to resources are then repeated. These measures include eating, drinking, social and sexual access, motility, grooming and biochemical estimates of cortisol and testosterone. Results. Subordinate animals have significantly less access to resources, both in the stable colony and when the formerly dominant animals become subordinate. Conclusions. A sociobiological approach using a hierarchy model equating resource-holding potential with self-esteem, exemplified by this study, may provide new concepts and insights into the phenomenology and pathophysiology of depression. It allows comparisons to be made between animal behaviour and cognition: the lack of such has been a major difficulty in animal studies hitherto. The findings are possibly more relevant to dysthymia than to affective disorder and imply a relationship between low resource-holding potential in sub-human animals as a phylogenetic antecedent of some of the cognitive and affective aspects of depression in man.