Implication of evolutionary theory for psychiatry

Delighted though I was to see Abed's editorial on evolutionary theory (Abed, 2000), I have reservations about its ability to provide an integrated scientific psychiatry as the author implied. Rather, it provides a welcome additional frame of reference. Like all ultimate theories, it applies to everything but lacks power with specifics (for example, to clarify whether an antidepressant or psychotherapy is best for an individual patient). Evolutionary theory seldom generates new treatments. It offers ultimate causes over which we have no control.

Although I am an enthusiast of both, I am concerned that evolutionary theory has the same drawback as psychodynamic theory; it can accommodate any combination of facts. If I devise and test a theory that adolescent males will be less or more inclined to form lasting sexual relationships than older men, I can explain either. If they desire to form casual relationships, then I can argue that in the ancestral environment this benefited their genes at a stage in life when it was difficult to get a permanent mate. And if they do not, I can argue that their male ancestors propagated best by acquiring a mate in youth, reserving infidelity until later. Hence, it is difficult to establish whether a proximate or ultimate cause has determined the outcome. A true sociological explanation for the sexual strategies of adolescent males might be hidden by our adherence to evolutionary theory. Furthermore, the specific evolutionary mechanism alongside the sociological mechanism might be different from the one proposed.

An unmentioned benefit of evolutionary theory is reassurance. If cyclothymia was adaptive in the ancestral environment (by optimising peak function), then the risk of depression may have been increased in subsequent generations. Instead of ‘defective’ we can think of ourselves as highly adapted. When vandals wreck the playground where my children play I can reflect that this is normal behaviour for male primates. By exerting themselves against the environment they intimidate rivals — a pleasant zoological perspective preferable to saying that society is falling apart.