The evolutionary diagnosis of mental disorder.

Medicalization of human behavioral diversity is a recurrent theme in the history of psychiatry, and the problem of defining what is a genuine mental disorder is an unresolved question since the origins of clinical psychopathology. Darwinian psychiatry can formulate a definition of mental disorder that is value free and based on factual criteria. From an evolutionary perspective, genuine mental disorders are maladaptive conditions. The ultimate function of an adaptation is gene propagation via maximization of survival and reproduction. It follows that a distressing and/or disabling psychological or behavioral syndrome is a psychiatric disorder only if it impacts negatively on the individual's inclusive fitness. However, in many cases, an evolutionary definition of disorder cannot be reconciled with current social values. Thus, clinicians adopting the evolutionary approach should conform to the prevailing trend of contemporary medicine and accept that their task is to be healers of the distressed, not watchdogs of biological adaptation. These pragmatic considerations do not minimize the scientific validity of the Darwinian definition of mental disorders. Probably, its major contribution to psychiatric theory is the elimination of the necessity to find a brain lesion or dysfunctional mechanism to validate the distinction between disorders and non-disorders.