The Evolution-Depression Paradox
The theory of evolution has consistently been backed up by peer reviewed study after peer reviewed study, but the presence of depression has been largely unexplained by evolution.
Yearly, 14.8 million Americans suffer from depression1, and anywhere from 30 to 50% of the United States population may suffer from depression at some point during their lifetime2. In theory, natural selection (a key mechanism of evolution in which only traits that best suit organisms to their environment survive) should have removed this disorder from our species or lessoned its impact, yet these high depression rates still exist.
In response to this apparent paradox evolutionary psychologists have come up with a controversial theory – that depression has an evolutionary purpose which can be beneficial.
Evolutionary Depression Theories
In a paper by evolutionary psychologists Paul Andrews and Andy Thomson titled "The Bright Side of Being Blue", a different idea about depression is expressed. They theorize that depression is not maladaptive3. Specifically, they look at the concept of rumination which is focusing to the point of obsession on a specific problem. This is typically seen as maladaptive because it is difficult to disrupt and leads to poor concentration in other areas. A person's focus on a problem can be so deep that personal hygiene is ignored. However, Andrews and Thomson believe this actually has a beneficial purpose as do many people who suffer from depression.
They created a concept to express the benefit called the analytical rumination hypothesis which describes an evolutionary depression. This argues that depression is actually a response to complex problems and that rumination actually minimizes disruptions so the analysis of complex problems can be conducted to solve them.
While this idea of an evolutionary depression is still very controversial, some have taken this information and applied it to therapy. Others remain critical of the evolutionary theory and say that such a damaging disorder cannot have an overall positive effect on the sufferer.
Changes to Treatment
Andy Thomson is a psychiatrist affiliated with the University of Virginia where he also practices privately. Until a few years ago, he employed a medication heavy approach to treat his depressed patients, but Dr. Thomson found that patients taking medications were likely to relapse back into depression4. However, patients who received talk therapy were less likely to relapse than those treated with medication. This observation and some in-depth talks with Paul Andrews lead to a change in his treatment approach. This new approach had a talk therapy focus, but it differed from conventional cognitive behavioral talk therapy.
Dr. Thomson found that patients had larger underlying social problems which affected their depression and often triggered it3. He felt that anti-depressants treated the symptoms and not the cause of depression which were these social problems. Cognitive behavioral therapy tries to disrupt rumination, so people can return to a normal level of functioning. However, Thomson believes that rumination is necessary for curing the depression and that disrupting this process only prolongs the episode.
Dr. Thomson's treatment approach helps the depressed person to identify the social problems which triggered their episode and then he helps them to solve those problems. A tool to accomplish this is expressive writing where the depressed person is encouraged to write about their depressive thoughts and feelings. This helps to gain insight into their problems which can then be solved with the help of the therapist. Dr. Thomson argues that this approach shortens the depressive episode and combats a relapse of depression.
References
2. https://www.scientificamerican.com/article.cfm?id=depressions-evolutionary
3. https://sites.google.com/site/paulwandrewsphd/home/andrews_pr_2009-1
4. https://www.nytimes.com/2010/02/28/magazine/28depression-t.html?pagewanted=1&_r=1