The Great Paradox:
An Evolutionary Accounting for Depressive Disorder

In the realm of abnormal psychology, most personality disorders truly are abnormal. For example, the highest projected percentage of those in the United States suffering Obsessive Compulsive Disorder is 2% (OCD). Globally, only 1.1% of the population is diagnosed with Schizophrenia (Schizophrenia). Another debilitating condition, Borderline disorder is just as uncommon – with 1 – 2% of the population reported as suffering from this affliction (Mental). The rarity of psychological disorders makes sense under the theory of evolution. The mind is a machine that has been fine-tuned from the primitive designs of our ancestors, and after thousands of years of descent with modification, through the vehicle of natural selection, we should expect that such mental “malfunctions” are exceptional. As anticipated, most major personality disorders are truly unusual.

However, one particular disorder has been preserved in our evolutionary psychology and is rampant among the population. Levels of major Depressive Disorder reign throughout humanity, and this fact is seemingly independent of environmental factors. The World Health Organization has conducted research that claims that roughly 15% of the population in industrialized nations is diagnosed with depression and that 11% of the population of developing nations can be diagnosed by the same criteria (Global). The official criteria for this psychological diagnosis is found in the DSM and claims a patient must display 5 of the 9 following symptoms:

1) depressed mood most of the day, 2) markedly diminished interest or pleasure in all, or almost all, activities, 3) significant weight loss when not dieting or weight gain, or decrease or increase in appetite nearly every day, 4) insomnia or hypersomnia nearly every day, 5) observable psychomotor agitation or retardation, 6) fatigue or loss of energy nearly every day, 7) feelings of worthlessness or excessive or inappropriate guilt, 8) diminished ability to think or concentrate, or indecisiveness, 9) recurrent thoughts of death, recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide. (DSM IV)

All of these DSM requirements are seemingly counter-productive to evolution (most disorders are counter-productive, hence their rarity) such that an individual suffering from depression is less inclined to reproduce, has a stifled appetite, experiences energy loss, has their decision making abilities deteriorate, and contemplates ending their own life. Such an affliction could be easily explained away under evolutionary theory if the disorder only occurred later in life (after the prime age of reproduction had passed), however depression strikes many adolescents and young adults. In fact, rates of depression among youth are higher than those among the mature in age (Teen). Evolution thus has an immense burden to explain why depression has been preserved in our species psychological make-up and even strikes at the time when we should be most intent on reproduction. A plausible explanation might be the idea that depression is our inability to catch up to our societal pressures (much like our evolutionary craving for fat and sweets has now increased obesity rates as the availability of food has increased) – however, many indigenous, primitive people groups have been recorded with similar rates of depression as highly industrialized nations (Andrews and Thompson). If scientists cannot blame society and culture for the emergence of depression, they must take up a view that incorporates the theory of evolution. And so researchers seeking to defend Darwin’s grand theory have decided to take up the project of proving depression as an evolutionary adaptation.

Research that reinforces the need for an evolutionary accounting of depression is the particular study of the brain chemical 5HT1A receptor. This molecule attaches to serotonin, another brain molecule linked to depression. Rodents without 5HT1A display less depressive symptoms in response to stressful stimuli. When researchers have compared the organization and make-up of the rat 5HT1A receptor to the 5HT1A of humans, it proves to be nearly identical “which suggests that it is so important that natural selection has preserved it. The ability to ‘turn on’ depression would seem to be important, then, not an accident (Andrew and Thompson).” So it appears that the tendency towards depression has been left intact as a vital part of our evolutionary psychology, but what benefits could this mental health disorder possibly present?

One conceivable explanation of benefits offered by depression is the occurrence of psychological ruminations. Ruminations are the reoccurring presence of negative, reflective thoughts such as, “why didn’t my marriage work?” And supposedly such thought processes could be beneficial for problem solving – a man going through the motions of divorce might begin to break down the ending of his relationship into “bite-size” morsels of thoughts to chew on mentally, and thus be able to analytically examine his failed relationship (Lehrer). However, such obsessive negative thoughts often reinforce the depression and bombard the human stream of consciousness, thus most psychologists attempt to stifle the rumination cycle by leading patients into positive thinking (Lehrer). Yet two researchers, Paul W. Andrews and J. Anderson Thompson, Jr., questioned if ruminations could actually prepare the human mind for change and help them learn valuable insights into their social relationships. If so, it might be the case that depression is actually an adaptation rather that a detrimental disorder. Although there are, of course, definite evolutionary costs to depression, scientists are proposing that the disorder might actually offer “net benefits (Lehrer).”

However, other scientists remain critical to this theory. Although the beneficial rumination theory might be a proper explanation for short term depression, or reactionary depression that results from grief (death) or traumatic circumstances (injury or loss), it does not help to explain the wide range of forms of depression, most notably: post-partum and long-term, constant major depressive syndrome. In the case of post-partum depression occurs after a mother has give birth and thus produces feelings of worthlessness and fantasies of suicide in a parent that should be investing enormous amounts of energy into insuring her offspring’s survival. Roughly 13% of new mothers face these “baby blues,” (Depression) making this disorder too common for evolution’s accounting system. It seems that there are no net benefits to post-partum depression. Again, the rumination theory falls short in the case of constant, major depressive disorders that are sustained for long periods of time. In this circumstance, ruminations are not helping a patient sort out his life, but rather the ruminations are destroying his rational thought processes. Ruminations are not always as helpful as, “what went sour in this relationship?” Instead, more commonly they form as “a long lament, a portrait of a mind hating itself, filled with sentences like this: ‘What terms might be used to describe such a solipsistic, self-consumed, bottomless emotional vacuum and sponge as she now appeared to herself to be (Lehrer)?’” This sort of self-depreciating, detailed accounting of loathing can not give way to an insightful social benefit, but instead “the dark thoughts of ‘The Depressed Person’ soon grow tedious and trying, but that’s precisely […, the] point. There is nothing profound about depressive rumination. There is just a recursive loop of woe (Lehrer).”

Another common answer to the question of depression in evolutionary psychology attempts to address depression in the youth. This proposal claims that if a young person experiences mild depression early in life as the result of a failed accomplishment, they are more likely to reassess their goals (Evolutionary). After this reassessment, the patients will set a more achievable goal for themselves and by setting a new, easier goal they are also securing a higher chance at long-term happiness. Such that, a youth who plans to be president, but fails at being elected to student government might reassess his overly ambitious goal in a state of depression and settle a little lower for becoming a lawyer – (a goal, that with persistence is difficult, but definitely achievable) and thus the youth’s temporary and mild depression has acted as a mechanism for assuring his future’s meaningfulness and joy. Thus it is asserted that mild, temporary depression is a small cost to pay for a future of happiness (Evolutionary).

However nice this hypothesis may seem, it simply doesn’t align with the facts of how depression truly functions. Rarely do people experience a single bout of depression in which they fully recover with no relapses. In a recent study of nearly 200 teenagers diagnosed with depression, 96% of the patients recovered fully or improved significantly after the first round of depression, however “47% had one or more subsequent depressive episodes in an average of two years. The type of treatment received made no difference […] teens treated with a combination of medication and cognitive behavioral therapy appeared just about as likely to suffer subsequent depressive episodes (O’Shea).” If the goal-reassessment hypothesis was true, the majority of these teens should have realized their ambitions, recalculated their capabilities, and then embarked on their new missions with sustainable happiness. Yet depression rarely works this way, those that experience one round of depression often experience later depression, thus it is an inaccurate depiction of the disorder to claim that it safeguards us against future unhappiness.

It is clear from human psychology and physiology, as well as the high rates of depression, that sadness must serve a purpose in life. As naturalistic scientists attempt to offer evolutionary explanations for this paradox, more questions arise. The rumination-hypothesis and the goal-assessment theory are merely a few claims among many that have recently emerged,

There is, for example, the “plea for help” theory, which suggests that depression is a way of eliciting assistance from loved ones. There’s also the “signal of defeat” hypothesis, which argues that feelings of despair after a loss in social status help prevent unnecessary attacks; we’re too busy sulking to fight back. And then there’s “depressive realism”: several studies have found that people with depression have a more accurate view of reality and are better at predicting future outcomes. While each of these speculations has scientific support, none are sufficient to explain an illness that afflicts so many people (Lehrer).

For objective scientists who are less intent on forcing a Darwinian explanation for the problem, this paradox signals red flags for evolutionist’s theory. There is definitely a question as to what possible function this disorder could serve under the tenets of evolution, but none doubt there must some purpose for the high rates of depression and the survival of this “malfunction” among the species. Depressive ruminations do not attempt or help to solve problems; rather, they obsessively describe the problem, which is our own depraved human nature. The human mind has an internal spotlight that redirects us again and again to our own insufficiency, channeling energy and attention (“human attention is a scarce resource — the neural effects of depression make sure the resource is efficiently allocated (Lehrer)”) to the very darkest parts of our human psychology. Working from my personal presuppositions about the Nature of Reality and the Supernatural, I find the presence of depression to be an internal magnifying lens that presses us to face our own lacking, and then turn to the One Who Lacks Nothing – Christ Jesus. Thus, depression exists for this reason,

to keep me from exalting myself, there was given me a thorn in the flesh, a messenger of Satan to torment me — to keep me from exalting myself! Concerning this I implored the Lord three times that it might leave me. And He has said to me, “My grace is sufficient for you, for power is perfected in weakness.” Most gladly, therefore, I will rather boast about my weaknesses, so that the power of Christ may dwell in me. Therefore I am well content with weaknesses, with insults, with distresses, with persecutions, with difficulties, for Christ’s sake; for when I am weak, then I am strong. (New American Standard Bible, 2 Corin. 12.7-10)

Works Cited

Andrews, Paul W. and Thompson Jr, J. Anderson. “Depression’s Evolutionary Roots.” Scientific American. 8/25/09. Accessed 2/20/12.

“Depression During and After Pregnancy.” Women’s Health. 3/06/09. Accessed 2/20/12.

“DSM IV Major Depressive Episode.” Depression Today. Accessed 2/20/12.  

“Global Depression Statistics.” Science Daily. 7/25/11. Accessed 2/20/12.

Lehrer, Jonah. “Depression’s Upside.” A version of this article appeared in print on 2/28/10, on page 38 of the Sunday magazine. The New York Times. 2/25/10. Accessed 2/20/12.

“Mental Illnesses: Borderline Personality Disorder” National Alliance on Mental Illness. Accessed 2/19/12.

“OCD Facts and Figures.” Understanding Obsessive Compulsive Disorder. Accessed 2/20/12.

O’Shea, Dennis. “Teen Depression likely to Reoccur.” Futurity. 11/2/10. Accessed 2/20/12.

“Schizophrenia Facts and Statistics.” Schizophrenia. 2010. Accessed 2/20/12.

“Teen Depression Statistics.” Teen Depression. Accessed 2/18/12.

“The Evolutionary Origin of Depression: Mild and Bitter.” Taken from the print edition. The Economist. 6/25/09. Accessed 2/20/12.