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The biology of mental disorders: What are we talking about?
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Borsboom et al. contrast the symptom network model with biological explanations of psychopathology and conclude that mental disorders cannot be explained in terms of biology. In fact, their conclusion is based on a biased and flawed description of the biological study of human mind and behavior. They reduce biological explanations of mental symptoms and disorders to abnormal neurobiological mechanisms and defective brain circuits. Even though such a reductionist model is still frequently encountered in the research and clinical literature, it is not illustrative of how biological explanations can improve our understanding of the origin of mental disorders. After the Darwinian revolution, biology is not only the study of the operation and interaction of structural elements, from molecules up to organs and whole individuals (functional biology). Modern biology is also the study of adaption and phylogenetic history (evolutionary biology) (Mayr 1982). When applied to psychiatry, the evolutionary approach shows that the biology of mental disorders is not just “neurobiology and genetic constitution” but also the study of evolved reactions to adverse environmental circumstances, including adaptive symptoms and calibrated life history strategies (Troisi 2017). Keller and Nesse (2006) introduced and tested a new framework for understanding the adaptive significance of depressive symptoms. Their hypothesis (the “situation-symptom congruence” hypothesis) predicts that, if different depressive symptoms serve different evolved functions, then different events that precipitate a depressive episode should give rise to different symptom patterns that increase the ability to cope with the adaptive challenges specific to each situation. The hypothesis was tested by asking 445 participants to identify depressive symptoms that followed a recent adverse situation. Guilt, rumination, fatigue, and pessimism were prominent following failed efforts; crying, sadness, and desire for social support were prominent following social losses. These significant differences were replicated in an experiment in which 113 students were randomly assigned to...