I recently read a book called “The Depth: The Evolutionary Origins of the Depression Epidemic“. Here is a summary of the book from Amazon:
Why are we losing the fight against depression? In this groundbreaking work, psychologist Jonathan Rottenberg explains that despite advances in pharmaceutical science, progress has been hampered by our fundamental misunderstanding of depression as a psychological or chemical defect. Instead, Rottenberg introduces a surprising alternative: that depression is a particularly severe outgrowth of our natural capacity for emotion; it is a low mood gone haywire. Drawing on recent developments in the science of mood—and his own harrowing depressive experience as a young adult—Rottenberg explains depression in evolutionary terms, showing how its dark pull arises from adaptations that evolved to help our ancestors ensure their survival.
For a good part of the book the author tried to make a case that mild depression is the same as major depression and if mild depression( reactive depression) is the same as major depression( endogenous depression) then neither is a disease. According to him they both have the same causes, similar symptomatology, and respond to similar treatments, therefore they are the same. This didn’t seem like an air tight argument to me since there are some things that have similar causes, similar symptomatology, respond to similar treatments and yet are different. For example Subictal Mood Disorders (epilepsy) and Bipolar disorder are exacerbated by stress and can display similar symptomology( mood changes) but yet could have different pathology.
Additionally, one person has argued that the term major depression includes too many people who might not necessarily have endogenous depression. What the author should have possibly been comparing is mild depression to melancholic depression in order to make his case. Melancholic is considered by many to be more endogenous in nature than major depression which might include more of the neurotic/reactive variety.
Another argument that he makes is that depression could be evolutionarily favorable. He makes a better argument here except severe depression doesn’t seem to be for the most part evolutionarily favorable. He specifically mentions an experiment where severely depressed people were a better judge of character than controls however this was just one experiment.
The author argues that depression is evolutionarily favorable since it causes people to stop pursuing impossible goals which are causing unnecessary stress. This seems plausible for mild depression which appears to make people more realistic but not so much for severely depressed people since they often have a distorted view of reality.
In conclusion his evolutionary theory in relation to mild depression was quite interesting and gives depression a more positive image but the inclusion of severe depression needs a stronger argument.