Phylogenetic Origins of Depression

Abstract

In this bachelor thesis I examine the phylogenetic origins of unipolar depression. Depression has many economic, social and personal cost, but current treatment does not work for many people and relapse rates are high. It has been suggested that understanding the etiology and why humans are vulnerable to psychopathology in the first place can be beneficial in terms of improving treatment practices. Some evolutionary psychologist has argued that clinical depression is a discrete adaption while others argue that it is a malfunction of the adaptative capacity for low mood. I account for the arguments of each field and subsequently for behavioral genetic findings on depression and three models of genetic variation from evolutionary genetics which explain why natural selection has not eliminated susceptibility alleles for psychopathology. Next I discuss how behavioral genetics and evolutionary psychology can be used eclectically to identify ultimate causes of depression based on an analysis of the fields’ similarities and differences. I argue that no incommensurable differences in meta-theory or philosophy of science exist, which would complicate the eclecticism. Moreover, if a phylogenetic explanation of individual commonalities and differences in vulnerability to depression is to be done, both fields are needed. I conclude that clinical depression is likely not an adaption in itself, but rather a result of polygenic mutation-selection balance leading to a continuum of affect reactivity interacting with adaptive time-lags and other genotype-environment interactions, to produce dysregulations in the adaptive capacity for low mood.

Bedømmelse: 12