Depression is one of the most common mental disorders in the U.S., affecting individuals of all ages (NIMH, 2018). Recent research has brought to life possible evolutionary reasons for the upbringing of depression in modern years.
Galecki and Talarowska
suggested depression is a form of adaptation to high requirements of the
environment (Gałecki & Talarowska, 2017). According to the authors, as our frontal lobe developed, we
gain the ability to verbal communication and it became the motivational and
conceptual control stations of human activity (Gałecki & Talarowska, 2017). As new stress factors were
added to our everyday life over the last several decades, imperfections of the
human brain started to show in the form of mood disorders (Gałecki & Talarowska, 2017). Dysfunction of
connections between the medial prefrontal cortex and the remaining parts of the
brain, mostly the ones associated with emotional stimuli interpretation,
results in depression (Gałecki & Talarowska, 2017). The evolutionary changes of our brains could not
keep up with the pace of modern days' intensive civilization changes, and
depression symptoms emerge as an adaptation to the new environment (Gałecki & Talarowska, 2017).
Complementing that, some authors suggest depression is an
adaptation to lead people to think intensively about their problems and
break them down into smaller components, in order to consider them one at a
time, a process known as rumination (Andrews, 2009). Depression leads to changes in the
brain such as the increased serotonin 1A (5-HT1A) receptor binding across
several regions of the brain that are involved in mood regulation (Kaufman, DeLorenzo, Choudhury, & Parsey, 2016). Studies
have shown that 5-HT1A receptors are involved in supplying neurons
with fuel needed to fire, as well as preventing them from breaking down (Andrews, 2009).
This event allows for ruminations to occur without causing a lot of damage to
the ventrolateral prefrontal cortex (VLPFC), the region where neurons must fire continuously
to avoid distractions.
5-HT1A receptors consist of G-protein-coupled
receptors that induce activation of hyperpolarizing K+ channels upon
serotonin (5-HT) binding (Kaufman, DeLorenzo, Choudhury, & Parsey, 2016). High densities of this receptor are seen in the
neocortex (Kaufman, DeLorenzo, Choudhury, & Parsey, 2016). They are distinguished into pre-synaptic (autoreceptors) and post-synaptic
(heteroreceptors) and have different responses upon sustained serotonin receptor
stimulation (Kaufman, DeLorenzo, Choudhury, & Parsey, 2016). The first is responsible for 5-HT reuptake from the synaptic
cleft, a mechanism in which anxiolytic and anti-depressive Selective Serotonin
Reuptake Inhibitors (SSRIs) medication is based upon (Kaufman, DeLorenzo, Choudhury, & Parsey, 2016).
Based on this line of thinking, studies have shown that depressed
people at better at solving social dilemmas by better analysis of the costs and
benefits of the different options that they might take (Andrews, 2009). Therefore, depression
is the environments’ way to demonstrate one has a complex social problem that
their brain is intent on solving (4).
These studies can give us evidence that contemporary stress
factors contribute to the evolution of depression in humans. Either by the increase of 5-HT1A receptors in
order to allow rumination and problem-solving or due to civilization changes occurring
at a faster pace than evolutionary changes, this gives us an insight into how
depression, like many other civilization diseases, evolved as an adaptation to
our new environment.
References:
Depression. (n.d.). Retrieved April 22, 2021, from https://www.nimh.nih.gov/health/topics/depression/index.shtml
Gałecki, P., & Talarowska, M. (2017, May 13). The evolutionary theory of depression. Retrieved April 22, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5439380/
Andrews, P. (2009, August 25). Depression's evolutionary roots. Retrieved April 22, 2021, from https://www.scientificamerican.com/article/depressions-evolutionary/
Kaufman, J., DeLorenzo, C., Choudhury, S., & Parsey, R. (2016, March). The 5-HT1A receptor in major depressive disorder. Retrieved April 22, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5192019/
This is an excellent blog post Victoria! Mental disorders in general have become far more prevalent in their diagnosis in recent years, but your research and explanation on depression I found to be both intriguing and well explicated. I thoroughly enjoyed your detailed analysis of the physiology, cause, and impact of depression on a given individual and how you conclude that modern stress factors have contributed to the evolution of depression in humans. Fantastic job!
ReplyDeleteThis is a great post, such an interesting read. I had not considered depression as a disease of civilization, but it totally is. "Therefore, depression is the environments’ way to demonstrate one has a complex social problem that their brain is intent on solving" - Wow, my mind is blown.
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