Depression Research Questions
This pillar is still a very ambiguous project concerning the evolutionary origins of depression. A brief summary of my thoughts that form the basis of my questions:
Anxiety has a clear evolutionary origin, wherein the "fight or flight" response is inappropriately engaged in an exaggerated manner. However, while the response is aberrant, the origin of this mechanism has a clear survival benefit. Conversely, depression is not usually discussed in similar terms of evolutionary adaptation. Nonetheless, the fundamental feature of fatigue experienced in depression may highlight that depression is in fact also a maladaptation of an evolutionary survival mechanism relating to energy conservation.
Firstly, fatigue is not only a diagnostic hallmark of depression according to the DSM-5 (REF), but has also been shown to be highly co-morbid with and correlated to depression @corfield_2016 . Secondly, comparisons have also been made between altered metabolic function of hibernating mammals (bears) and clinically depressed patients @tsiouris_2005 . Finally, specific environmental changes leading to depression (such as seasonal affective disorder) ( @eagles_2004 ) or indeed the effectiveness of specific treatments (e.g. exercise as intervention) ( @barbour_2007 ) also might highlight an underlying root cause.
When considering the theoretical frameworks of depression, there are many existing theories that may be unified by a higher level view of depression as a maladaptive mechanism of energy conservation. For example, the monoamine hypothesis, a theory in itself limited, may be further supported by the understanding that serotonin (5-hydroxytryptamine; 5-HT) plays an important role in initiating and maintaining hibernation in some mammals ( @haak_1991, @canguilhem_1986 ). Similar high-level comparisons may be drawn to other frameworks and features of depression, both on the neurobiological/ physiological level, as on a behavioural level.
Another key piece of evidence may be found in the "Mitochondrial Hypothesis" of depression, implicating abnormal mitochondrial function as an underlying mechanism (reviewed in @ferrari_2017 , @gardner_2011 , @bansal_2016 ).
The current aims are as follows
- Write a high-level overview review outlining existing evidence through the lens of energy conservation adaptations
- Plan (and carry out) a data-based experiment using specific data, where alternative analysis might yield a potential target for further experimentation
1 References
Bansal, Y., Kuhad, A., 2016. Mitochondrial Dysfunction in Depression. Curr Neuropharmacol 14, 610–618.
Barbour, K.A., Edenfield, T.M., Blumenthal, J.A., 2007. Exercise as a Treatment for Depression and Other Psychiatric Disorders: A REVIEW. Journal of Cardiopulmonary Rehabilitation and Prevention 27, 359–367.
Canguilhem, B., Miro, J.L., Kempf, E., Schmitt, P., 1986. Does serotonin play a role in entrance into hibernation? American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 251, R755–R761.
Corfield, E.C., Martin, N.G., Nyholt, D.R., 2016. Co-occurrence and symptomatology of fatigue and depression. Comprehensive Psychiatry 71, 1–10.
Eagles, J.M., 2004. Seasonal affective disorder: a vestigial evolutionary advantage? Medical Hypotheses 63, 767–772.
Ferrari, F., Villa, R.F., 2017. The Neurobiology of Depression: an Integrated Overview from Biological Theories to Clinical Evidence. Molecular Neurobiology 54, 4847–4865.
Gardner, A., Boles, R.G., 2011. Beyond the serotonin hypothesis: Mitochondria, inflammation and neurodegeneration in major depression and affective spectrum disorders. Progress in Neuro-Psychopharmacology and Biological Psychiatry, The Neuro-inflammatory and Neuroprogressive Pathways in Depression 35, 730–743.
Haak, L.L., Mignot, E., Kilduff, T.S., Dement, W.C., Heller, H.C., 1991. Regional changes in central monoamine and metabolite levels during the hibernation cycle in the golden-mantled ground squirrel. Brain Research 563, 215–220.
Tsiouris, J.A., 2005. Metabolic depression in hibernation and major depression: An explanatory theory and an animal model of depression. Medical Hypotheses 65, 829–840.