Evolutionary approaches to major depressive disorder and the association with fitness hindrances

Major Depressive Disorder (MDD) affects 9.5% of Americans yearly and is the leading cause of disability within the United States (NIMH, 2001). Although numerous psychological and physiological theories of MDD are well-known, only recently have some theorists attempted to develop evolutionary theories for depression. These evolutionary approaches range from explanations of depression's origins to depression having adaptive capacity. Some of these perspective view depression as a beneficial response that aids in problem solving, rather than an outcome of malfunctioning cognitions or neurophysiology. To date, little evidence exists to support the evolutionary based hypotheses of MDD.; The first section of the study preliminarily examines the potential for evolutionary theory to provide predictive information on persons who are likely to become depressed. This was done by investigating the presence of fitness hindering events in depressives. The last section of the project involved testing predictions developed from various evolutionary hypotheses, including the Social Yielding Theory (Price & Gardner, 1995; Price, Sloman, Gardner & Gilbert, 1994; Sloman, Price, Gilbert & Gardner, 1994), the Social Navigation Hypothesis (Watson & Andrews, 2002), the Bargaining Hypothesis (Hagen, 1999, 2002), and the Hibernation Hypothesis (Glantz & Pearce, 1989). A standardized questionnaire was developed for the study. This and the Geriatric Depression Scale (Yesavage et al., 1983) were verbally administered to older adult participants (aged 50--93) from rural, southern Mississippi (n = 117). Of this sample, 67 were classified as "depressed" based upon scores of 11 or higher on the Geriatric Depression Scale (GDS) and a primary diagnosis of MDD by a licensed mental health professional.; Fitness hindrances were found to be a significant correlate of depression. Furthermore, all four evolutionary perspectives received some support, although the SNH had the highest number of predictions supported. This study demonstrates that evolutionary perspectives provide insight into the study of depression, as well as its treatment, and should be more seriously considered in future research.