title: An adaptationist perspective on the etiology of depression.
abstract: Major depressive disorder (MDD) presents with a variety of symptoms and responds to a wide range of treatment interventions. Diagnostic criteria collapse multiple syndromes with distinct etiologies into the same disorder. MDD is typically understood as a malfunction of neurotransmission or brain circuitry regulating mood, pleasure and reward, or executive function. However, research from an evolutionary perspective suggests that the "normal" functioning of adaptations may also generate symptoms meeting diagnostic criteria. Functioning adaptations may be an underappreciated etiological pathway to MDD. Many adaptive functions for depressive symptoms have been suggested: biasing cognition to avoid losses, conserving energy, disengaging from unobtainable goals, signaling submission, soliciting resources, and promoting analytical thinking. We review the potential role of these adaptive functions and how they can lead to specific clusters of depressive symptoms. Understanding MDD from such a perspective reduces the heterogeneity of cases and may help to select the best intervention for each patient. We discuss the implications of different adaptive and maladaptive etiological pathways for the use of antidepressants and various modes of psychotherapy. In particular, instances of MDD caused by functioning adaptations may benefit most from treatments that support the adaptive function, or that target the precipitating causal stressor. We conclude that an evolutionary approach to the study of MDD may be one of the more promising approaches to reduce its heterogeneity and to better match patients and treatment.
authors.affiliation: Social Aetiology of Mental Illness (SAMI) CIHR Training Program, Centre for Addiction and Mental Health (CAMH), Suite 1111, 33 Russell Street, Toronto, Ontario, Canada M5S 3B1; Evolutionary Ecology of Health Research Laboratories, Department of Psychology, Neuroscience & Behaviour, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1. Electronic address: duriskzt@mcmaster.ca.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Durisko
authors.affiliation: Centre for Addiction and Mental Health (CAMH), 1001 Queen Street West, Toronto, Ontario, Canada M6J 1H4; Department of Psychiatry, Faculty of Medicine, University of Toronto, 250 College Street, Toronto, Ontario, Canada M5T 1R8.
authors.forename: Benoit H
authors.initials: BH
authors.lastname: Mulsant
authors.affiliation: Evolutionary Ecology of Health Research Laboratories, Department of Psychology, Neuroscience & Behaviour, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1. Electronic address: pandrews@mcmaster.ca.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Andrews
mesh_terms: D000203:Activities of Daily Living; D000223:Adaptation, Psychological; D000328:Adult; D000928:Antidepressive Agents / Q000627:therapeutic use; D003071:Cognition; D003863:Depression / Q000188:drug therapy / Q000523:psychology*; D003865:Major Depressive Disorder / Q000188:drug therapy / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D009435:Synaptic Transmission
chemical_list: D000928:Antidepressive Agents
keywords: Darwinian Medicine; Evolution; Evolutionary Psychiatry; Major depressive disorder