Darwinian Depression

Depression: A Darwinian Approach
By: Brendan Carmicheal

Depression is a devastating illness said to affect about 18.8 million adults in the United States (SFN
2005) and about 5% of the Canadian population each year (Firestone and Marshall 2003). This disease takes a toll on Canadians - costing the population $27 billion dollars annually in health care, medications,
unemployment, days absent or permanent disability expenses (Firestone and Marshall 2003).
The Darwinian perspective states that any given genetic mechanism or trait has evolved due to its survival value. Therefore depression should be no different. Yet how could something that creates so much misery be adaptive? Read on and find out the possible reasons!!

Symptoms
- Persistent feelings of sadness
- Loss of interest or ability to feel pleasure
- Feelings of worthlessness or guilt

(Source: Firestone and Marshall 2003. For further information on symptoms please see:http://www.mentalhealth.com//dis1/p21-md01.html )

Proximate Causes

The Diathesis-Stress Model of Depression

Some people inherit a diathesis (a genetic predisposition for developing depression) that is only initiated when the person experiences a stressful life circumstance (Pinel 2002). Support for this approach comes from the evidence that demonstrates how depressed subjects have much higher levels of certain stress hormones then people who are not depressed (SFN 2001). (For more info please see:
http://web.sfn.org/content/Publications/BrainBriefings/brain_depression.html)

Monoamine Theory of Depression

Those who have a shortage of certain types of monoamines such as dopamine, norepinephrine or serotonin experience depression due to decreased amount of activity in certain brain regions (Firestone and Marshall 2003)

Evolutionary Causes

Depression deals with the notion of evolutionary legacy (Nesse and Williams 1996). That is to say the mechanism for depression had more of an adaptive value in our ancestors perhaps millions of years ago and it is not a mechanism in which we can just easily select-out without making major structural changes. For instance, it has been speculated that the serotonin system, which, "...may function, in part, to mediate status hierarchies and that some low mood may be a normal part of status competitions" (Nesse and Williams 1996), has evolved for perhaps millions of years.

http://www.telegraph.co.uk/

Social Competition Hypothesis

In primates, depression evolved as a mechanism to inhibit the given primate from challenging those of higher status (Rossano 2003). Advantages include: 1) signaling to others a non threatening status; 2) allowing for involuntary submissiveness and 3) it withdrawals the individual from costly competition (Rossano 2003). The bout of sadness that may follow a loss, perhaps forces the individual to take "time out" and focus on a new strategy for interacting with the environment.

Interestingly, men who loose social status (perhaps as a result of competition), tend to display symptoms of depression (Rossano 2003). Similarly, the authors of the book �Why We Get Sick� (Nesse and Williams 1996) describe cases of how when alpha monkeys loose their dominant status their serotonin levels drop and they display human like symptoms of depression (Nesse and Williams 1996). The bout of sadness that may follow a loss, perhaps forces the individual to take time out and focus on a new strategy for interacting with the environment.

http://flatrock.org.nz/topics/animals/dont_blow_it.htm

Treatment

The most successful treatment for depression is a combined treatment of cognitive-behavioral therapy plus medication (Firestone and Marshall 2003). Cognitive-behavioral therapy entails targeting thoughts and behaviors that lead to depression and replacing these actions with more beneficial ones in their place. Popular choices of medication include Selective Serotonin Reuptake Inhibitors (SSRIs) such as Prozac or Paxol.

Can the evolutionary perspective teach us anything about treatment?

Yes! Perhaps by increasing the amount of serotonin in the brain, SSRIs work by tricking the brain into �believing� that the organism is an alpha male or female. Therefore perhaps we are already implementing the evolutionary treatment into our treatment for depression. If the monoamine hypothesis is correct � I wonder if we could some how increase the level of serotonin in the brain by working to empower the individual in their given environment, by somehow giving them the feelings of being the alpha. Also, I wonder if the stressful event that triggers depression in the stress-diathesis approach correlates with the feelings of being dominated in the brain. In other words � are the feelings of being dominated related to situations that induce stress thus leading to bouts of depression? Answers to these questions could perhaps provide us with new insights as well as new forms of treatment that target stress as well as targeting environmental influences.

References:

Firestone P, and Marshall WL. 2003. Abnormal Psychology: perspectives. 2nd ed.
Toronto: Pearson Education Canada Inc.

Long PW. 1996 Oct. Internet Mental Health. Available from:
http://www.mentalhealth.com//dis1/p21-md01.html Accessed 2005 June 25.

Nesse RM, Williams GC. 1996. Why we get sick. New York: Vintage Books. 290 p

Pinel, J.P. 2003. Biopsychology. 5th ed. Boston: Allyn and Bason. 566 p.

Rossano MJ, editor. 2003. Evolutionary Psychology. Hoboken NJ: John Wiley &
Sons, Inc. 488 p.

[SFN] Society For Neuroscience. Oct 2001. Brain Briefings. Available from:
http://web.sfn.org/content/Publications/BrainBriefings/brain_depression.html Accessed 2005 June 20.

[SFN] Society For Neuroscience. 2005. Depression � Making a Difference Today. Available from:
http://web.sfn.org/content/Publications/BrainResearchSuccessStories/BRSS_Depression.pdf Accessed 2005 June 20.

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