Evolutionary Approaches To Depression - Honest Signaling Theory

Honest Signaling Theory

Another reason depression is thought to be a pathology is that key symptoms, such as loss of interest in virtually all activities, are extremely costly to the sufferer. Biologists and economists have proposed, however, that signals with inherent costs can credibly signal information when there are conflicts of interest. In the wake of a serious negative life event, such as those that have been implicated in depression (e.g., death, divorce), "cheap" signals of need, such as crying, might not be believed when social partners have conflicts of interest. The symptoms of major depression, such as loss of interest in virtually all activities and suicidality, are inherently costly, but, as costly signaling theory requires, the costs differ for individuals in different states. For individuals who are not genuinely in need, the fitness cost of major depression is very high because it threatens the flow of fitness benefits. For individuals who are in genuine need, however, the fitness cost of major depression is low, because the individual is not generating many fitness benefits. Thus, only an individual in genuine need can afford to suffer major depression. Major depression therefore serves as an honest, or credible, signal of need.

For example, individuals suffering a severe loss such as the death of a spouse are often in need of help and assistance from others. Such individuals who have few conflicts with their social partners are predicted to experience grief—a means, in part, to signal need to others. Such individuals who have many conflicts with their social partners, in contrast, are predicted to experience depression—a means, in part, to credibly signal need to others who might be skeptical that the need is genuine.