This is essentially a makeshift term for the application of
evolutionary psychology to
psychiatry, the study of mental disorder. Explaining psychiatric conditions in terms of
evolution is for the most part a recent approach and it remains to be seen whether it will hold a place among the credible branches of science.
The basic thesis of evolutionary psychiatry is that mental disorders arise from inappropriate expressions of tendencies which originally proved adaptive. A simple example is the explanation of fears and phobias. An innate fearful reaction to danger would have been a survival advantage for early humans, and this fear survives in modern humans, even in situations where it is no longer appropriate. This is perhaps clear from the prevalance of fear of snakes among Westerners who've never even been near one. In another example Smith (1979) reports that a common reaction among infants in many cultures is to be scared of any unknown male. This may be a relic of the days when, hypothetically, murdering the children of a newly-acquired mate was a common strategy employed by males to ensure they didn't waste resources on another male's children.
An evolutionary explanation of depression is the so-called rank theory. Among early humans (particularly males), there would have been frequent, brutal fights for rank and status. (There still are, really.) The loser of such a fight may well have been better off accepting defeat than vainly trying to fight on and risk even more injury. The stimulus for this adaptive resignation would be the psychological phenomenon of depression. Conversely, the winner of the fight might secure his position with deliberately arrogant and hyperactive behaviour; perhaps the rank theory can also explain mania.
There is even an evolutionary explanation of schizophrenia, in Price and Stevens' audacious group-splitting hypothesis. They suggest that the fractured cognition and delusions of grandeur associated with schizophrenia would occasionally lead to the breaking off from one social group of a new band of people, following the deluded schizophrenic to a promised better life. In the case of groups whose size was starting to exceed that of optimum efficiency, this would be a benefit. Thus the occasional schizophrenic would be doing a favour to his kin by leading away those excess members intent on believing his wild promises.
Mainstream evolutionary psychology has enough of a hard time that a new, obscure, even more controversial offshoot of it may find it difficult indeed to find acceptance. Only time will tell whether this new approach to mental disorder will prove a success.
Reference: Mike Cardwell, Psychology for A Level, 2000