Depression's Evolutionary Roots

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Two scientists suggest that depression is not a malfunction, but a mental adaptation that brings certain cognitive advantages

By Paul W. Andrews and J. Anderson Thomson, Jr.

Depression seems to pose an evolutionary paradox. Research in the US and other countries estimates that between 30 to 50 percent of people have met current psychiatric diagnostic criteria for major depressive disorder sometime in their lives. But the brain plays crucial roles in promoting survival and reproduction, so the pressures of evolution should have left our brains resistant to such high rates of malfunction. Mental disorders should generally be rare — why isn't depression? This paradox could be resolved if depression were a problem of growing old. The functioning of all body systems and organs, including the brain, tends to deteriorate with age. This is not a satisfactory explanation for depression, however, as people are most likely to experience their first bout in adolescence and young adulthood.

Or, perhaps, depression might be like obesity — a problem that arises because modern conditions are so different from those in which we evolved. ** sapiens did not evolve with cookies and soda at the fingertips. Yet this is not a satisfactory explanation either. The symptoms of depression have been found in every culture which has been carefully examined, including small-scale societies, such as the Ache of Paraguay and the !Kung of southern Africa — societies where people are thought to live in environments similar to those that prevailed in our evolutionary past.

There is another possibility: that, in most instances, depression should not be thought of as a disorder at all. In an article recently published in Psychological Review, we argue that depression is in fact an adaptation, a state of mind which brings real costs, but also brings real benefits.

One reason to suspect that depression is an adaptation, not a malfunction, comes from research into a molecule in the brain known as the 5HT1A receptor. The 5HT1A receptor binds to serotonin, another brain molecule that is highly implicated in depression and is the target of most current antidepressant medications. Rodents lacking this receptor show fewer depressive symptoms in response to stress, which suggests that it is somehow involved in promoting depression. (Pharmaceutical companies, in fact, are designing the next generation of antidepressant medications to target this receptor.) When scientists have compared the composition of the functional part rat 5HT1A receptor to that of humans, it is 99 percent similar, 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.

This is not to say that depression is not a problem. Depressed people often have trouble performing everyday activities, they can't concentrate on their work, they tend to socially isolate themselves, they are lethargic, and they often lose the ability to take pleasure from such activities such as eating and sex. Some can plunge into severe, lengthy, and even life-threatening bouts of depression.

So what could be so useful about depression? Depressed people often think intensely about their problems. These thoughts are called ruminations; they are persistent and depressed people have difficulty thinking about anything else. Numerous studies have also shown that this thinking style is often highly analytical. They dwell on a complex problem, breaking it down into smaller components, which are considered one at a time.

more...

http://www.scientificamerican.com/article....ns-evolutionary

[almaty 19]

interesting view on major depression...but the article was to braod -based as there are other depression based reasoning besides organic in anture

[HAL 9000 96]

interesting view on major depression...but the article was to braod -based as there are other depression based reasoning besides organic in anture

It is a Sci Am article.

I like to think of many organic mechanisms as psychological in nature. 5HT1A R has a clear expression profile in the 'mood' centers of the brain that get used/misused. With misuse, the actual availability of these receptors tends to decrease (downregulation). That's the whole idea of 5HT reuptake inhibition- keep serotonin available in the synapse for a longer period of time to continually activate the receptors that are there in smaller amounts postsynaptically.

[almaty 19]

agree,..but some cause and effects of depression and depressive mood is behavioral or trauma enduced

[HAL 9000 96]

Yup... that too. I think there is a psychosomatic part of it as well... just remember that the organic component is the vehicle for acting out those behavioral manifestations.