Genes for depression part of adaptation?
Published on May 23, 2014 11:01 AM
Among 10 to 19-year-olds globally, depression is the main cause of disabling illness. This is according to Health for the World's Adolescents, a report that the World Health Organisation (WHO) released last week.
More accurately called major depressive disorder (MDD), it also tops the number of cases seen at the Institute of Mental Health (IMH). In Singapore, one in 16 people will have MDD at some point in life, according to a 2011 IMH survey. Locally, the median age at which symptoms first appear is 25 years but all ages can be affected.
Naturally, treatment is needed, especially because suicide is an ever present danger in MDD. Yet experts in an esoteric subdiscipline called evolutionary psychiatry believe that such patients should not be taking antidepressants.
A patient's wife called me to discuss The Depths: The Evolutionary Origins Of The Depression Epidemic (2014). This book argues that, although evolution has made humans the fittest species, we have nevertheless evolved to be subject to depressions. This suggests that depression promotes species survival in some way.
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Evolution is all about survival and reproduction. A specific trait that confers a genetic edge must lead to more offspring. Thus, if depression were really an adaptation passed down through natural selection, then patients should have more children than people without depression.