Department of Anthropology

Mental illness currently accounts for 11.5% of global disease burden, more than all cancers combined. Depression alone is now the fourth-leading cause of the global disease burden and the leading cause of disability worldwide. Suicide accounts for about the same number of deaths as all wars and homicides combined.

My research explores, in evolutionary-ecological perspective, mental health problems including depression, suicidality, deliberate self-harm, and addiction. Minor depression—low mood often accompanied by a loss of motivation—is almost certainly the psychic equivalent of physical pain. Major depression, however, is characterized by additional symptoms—such as loss of interest in virtually all activities and suicidality—that have no obvious utility. Given that the principle cause of major unipolar depression is a significant negative life event, and that its characteristic symptom is a loss of interest in virtually all activities, it is possible that this syndrome has two related functions.

First, it could be a costly and therefore honest signal of need to social partners with whom one has severe conflicts. Second, it could function somewhat like a labor strike. When powerful others are benefiting from an individual’s efforts, but the individual herself is not benefiting, she can, by reducing her productivity, put her value to them at risk in order to compel their consent and assistance in renegotiating the social contract so that it will yield net fitness benefits for her.

In partial support of these hypotheses, depression is associated with the receipt of considerable social benefits despite the negative reaction it causes in others. This framework also works well for suicidality and deliberate self-harm.