Darwinian evolutionary theory implies that certain design features in beings do not arbitrarily exist. The evolutionary designs provide evolved adaptations over time. For example, the bones of some birds are honeycombed structures, which are strong yet light enough for them to fly in the air. Or the typical fleshy leaves of the plant that grows in rocky mountain serve as a function of conserving water as there is very little soil around such plant to retain water.
Evolutionary psychology is also based on the premise that humans have evolved psychological and physiological mechanisms that help solve adaptive problems in the past. One of the good examples is emotion. Emotions are thought to have evolved in us to coordinate the activity of our body systems to fight survival and reproductive challenges that we have faced in the environment (Tooby & Cosmides, 1990). They can be seen as adaptations. When this view is applied to emotions, especially depression, the predominant classification of depression as a disorder (i.e. biological dysfunction of the mind, rather than evolved adaptation) is questionable.
Recently I read an article by Andrews and Thomson (2009) that tries to understand depression from evolutionary perspective. The depressive state they mentioned is strictly, restricted to unipolar depression characterized on a single continuum of severity, duration and liability (Krueger & Markon, 2006), not bipolar depression. I will mention some key ideas from the paper, though it could not suffice that of original information mentioned in the original paper. (For those of you who are interested in details, read full manuscript here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2734449/pdf/nihms129978.pdf )
American Psychiatric Association defines depression as an emotional state, along with sad mood, anhedonia (i.e. inability to get pleasure from various activities like sex or eating) and changes in psychomotor, sleeping and eating patterns. Mental disorders are typically defined in terms of biological dysfunction (APA, 2000). Yet, the concrete evidence of what biological dysfunction is not very specified. To meet criteria of depressed state as a disorder, DSM-IV specified that the presence of “clinically significant impairment or distress” (APA, 2000).
- Evolutionary Insight into Depression
Evolutionary psychology views that such impairment can be caused by biological dysfunction, but it can also can be caused by bodily response mechanism such as stress and fever. The impairment could be the adaptive outcome of tradeoffs, essential in our body systems to produce an effective and efficient response (Nesse & Williams, 1994). Just like, when you touch the hot stove and your body feels pain. But the pain goes away as you move yourself away from the stove. Or consider a time you shiver when you are cold; shivering warms your body. Or consider coughing and sneezing; the acts expel pathogens. Or consider the example of fever, which creates an uncomfortable situation for pathogens. These discernible symptoms of immune reactions are not caused by the infection itself but by your bodily response to the infection (Steinkopf, 2015). Following this view, Andrews and Thomson (2009) proposed the analytical rumination (AR) hypothesis and argued with research evidences that depressive state is an adaptation that evolved as a response to solve complex problems by over-thinking and analyzing the situation. Several claims were made in the paper.
- Higher prevalence estimates of depressed states in humans
One survey study reported that, 46.4% of people in the United States have met DSM-IV-TR criteria for at least one mental disorder at some point in their lives, and 16.6% have met criteria for major depressive disorder (Kessler, et al., 2005). Another study in New Zealand Christchurch also showed that by age 21, 37% of participants in the study met criteria for a life time DSM-IV episode of major depression (Wells & Horwood, 2004). Besides high prevalence findings in industrialized nations, the characteristics and features of depression have been found in every human culture in which the “disorder” is studied (Patel, 2001). Such high prevalence suggests that depressive disorder could represent proper psychological functioning and responses, rather than pathological disorder ( Horwitz & Wakefield, 2007).
- Complex social and analytical problems, especially fitness related issues, trigger depressed states.
Depressed people usually report that they face severe, depressed problems that are difficult to solve, have less confidence and focus more on the problems (Lyubomirsky et al., 1999). These problems depressed people face are usually social in nature (Brown & Harris, 1978). Interpersonal conflicts, especially with intimate social partners are very common in depressed (Hammen, 1992). In married couples, the risk for major depression increases about 40 times for those who are unhappily married (Weissman, 1987).
Such social problems could be traced back to evolutionarily related events such as living in groups, food sharing, raising children, guarding enemies, and finding and maintaining mates. While pursuing and maximizing self-interests and fitness, our ancestors must also have cooperated with the group without breaking the cooperation (Andrews, 2001).
To solve complex social problems, ones require analytical skills, breaking down into small parts and analyzing the situations. Such analytical skills are also helpful in future planning and prevention to the stressors in the future (Hammen, 1992). Such thoughts are called upward counterfactual thoughts (Roese & Olson, 1997). The counterfactual thoughts focus on what the different situations could have resulted when different actions are taken and by upward, such thoughts could help one take future actions that engender positive results.
- Ruminations and focus on dilemma and problems require energy and sustained attention, the result is a trade-off.
Depression maximizes current personal social problem but distances one from immediate reward such as (eating and sex) that would disturbs rumination process (Andrews and Thomson, 2009.) It also induces psychomotor changes like sleeping and activity patterns that could disrupt focus analysis of social problems by depressed. At the same time, depression also promotes solitude, and fatigue so that energy would be focused on the problem. Depression in analogy is like coughing and fever that purge the pathogens. Yet, the trade off is that it harms the bodily systems as well. Or consider risk-taking behaviors, more so by males than females. But the trade off is the risks involved (In the future, I will explore and write an article on male-risk taking behaviors from evolutionary perspectives).
The primary article continues to support AR hypothesis by giving research evidences on genes, neurotransmitters, and their receptors. From AR hypothesis, the authors also propose solutions for paradoxical findings from cognitive and behavioral genetics.
- Ruminations and sustained attentions should have concrete results in solving the problems.
Rumination for solving problems would be futile if the results are not actually effective. Au et al. (2003) studied the decision-making investments by business students based on various company business information. By inducing sad mood in participants in first round by telling them that they made bad investment, these sad participants made the most accurate decisions by making most profits in second rounds. Happy participants, with positive feedbacks in the first round, made worse decisions; they made less accurate judgment and fewer profits. The participants in neutral conditions were not as accurate as sad participants in their judgments but received a higher profit because they invested more.
Even in experiments that investigate strategies of depressed people in social dilemma games, depressed people outperformed normal subjects (97.4 points vs. 61.2 points) (Hokanson et al., 1980). (By the way, social dilemma games are types of prisoner dilemma situation in which, say you and your friends, are going to be in prisons because of the crimes. If you admit, but your partner does not, he will get 5 years of jail time. If your partner admits, but you do not, you will get 5 years of jail time. But if you two were both silent, both will only get 1 year of jail time. However when you both admit the crimes, you both get 10 years of jail time.) The main point here is that you maximize by cooperating, but you have to access the situations more analytically because people do not always cooperate especially in their self-interests.
Depressed people also are more realistic in assessing the situations while non-depressed people have more positive illusions and biases like (self-serving biases (you praise yourself, but not situations and other factors when you have positive results. One example is you get an A for the exam because you are clever and smart, not because the exam is easy or the teacher is good.) and external locus of control (When fail, blame situations. When succeed, praise yourself) (Taylor & Brown, 1988).
Depressed people may seek out more information for them to understand and insights about the problems. Depressed people prefer to interact with people who give them negative evaluations of their personalities than “healthy” people (Swann et al., 1992). The depressed may also analyze the situations by getting more focus on the problem while conserving energies for the analytical purpose on social and complex problems. The trade-off is distancing themselves from situations that interfere with the analytical purposes.
The bright side of the depression could be that the situations are accessed more accurately and improved over time. When in conflicts with close and social partners, people are also more willing to show more support, understanding and sympathy when their partners have depressive symptoms (Sheeber et al., 2011). From evolutionarily approach, depression is, not strictly classified as pathological disorder, but could be seen an evolved psychological and physiological in response to dealing with stressor.
Special thanks to the authors from primary article in sharing the insight. This wonderful article was written by Andrews and Thomson (2009). I am simply summarizing and understanding it more through writing . Those of you who are more interested in the beauty of details, please read the full article on the link above.
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