Can depression, anxiety and somatization be understood as appeasement displays?

Background: No satisfactory basis in normal function characterizes major depression and its co-morbid disorders. Yet these may represent maladaptive expression of adaptive communicational states exhibited normally in many species. Methods: We examined the signal value of depressive and anxious mood states, fatigue syndrome and somatoform disorders and found them to resemble appeasement or submission to conspecifics (members of a same species) as studied in other animals. Moreover, applying game theory formulations of conflict resolution and the triune brain theory of MacLean supported the hypothesis. Limitations: Direct experimental evidence must still test hypotheses that emanate from the presented framework. Conclusions: Implications for this approach include improved understanding and treatment of depression, improved research strategies, and a potential future pathogenesis-focused nosology.