Jane McCredie: Psyche selection

IF you were considering the various fields a psychiatrist in training might need to study, evolutionary biology probably wouldn’t be at the top of your list.

But a group of European and North American psychiatrists recently argued evolutionary theory could help to explain a range of clinical disorders and perhaps even point to new ways of tackling them.

Researchers who want to find a “contemporary and scientifically satisfying” understanding of psychiatric conditions need to take into account the roles that both environmental factors and natural selection have played in sculpting brain-based mechanisms and behaviour, they wrote in World Psychiatry.

In a perhaps provocative move, they even suggested the psychiatrists’ bible, the Diagnostic and statistical manual of mental disorders (DSM), could be reorganised along such lines, with disorders classified according to the evolutionary significance of behaviours.

The long-awaited DSM-5 is due out next year but there is no news that it will contain a lot of material on natural selection — although some might see the ever-controversial revisions as a Darwinian process in its own right.

The suggestion that some of our neural mechanisms and behaviours might have evolved to suit conditions in earlier human societies, but are less functional in our modern society, is not exactly new.

Such concepts may not be part of the normal language of psychiatry, but evolutionary psychologists have been playing with them for decades — sometimes to great effect, yet sometimes displaying a kind of oversimplified genetic determinism.

Not all of our behavioural dysfunction can be put down to a mismatch between genes evolved in the Pleistocene period and today’s fast-paced digital world.

Fortunately, these psychiatrists avoid that trap, highlighting the complexity of interactions between genes and environment.

Some alleles can, for example, predispose those who carry them to develop a particular psychiatric disorder if they experience maltreatment during childhood, while actually protecting them from the same disorder if they are raised in a favourable environment.

Far from portraying our life course as irrevocably determined by the genetic lottery we receive at conception, such findings could suggest that evolution has actually favoured plasticity — a high level of responsiveness to environmental conditions.

While that can leave us vulnerable to harm when those conditions are toxic, it may also raise hope that an evolved genetic predisposition can be modified by environmental factors.

In their call for an “evolutionarily informed psychiatry”, these authors suggest that a better understanding of the evolved basis of many common disorders might help patients to overcome them and clinicians to design more targeted therapies.

Many psychiatric disorders feature defences against perceived threats, they note, citing social anxiety disorder, obsessive-compulsive behaviours and paranoid ideation as examples.

It’s certainly interesting to wonder whether psychotherapy based on an understanding of the evolved nature of our response to danger might offer a new way to address such problems. Or whether an understanding of depression symptoms as evolved behaviours designed to minimise or avoid conflict might help in treatment of that condition.

It’s early days yet, but it will be interesting to see if Darwinian psychiatry makes it through the process of natural selection to become part of mainstream practice.

Jane McCredie is a Sydney-based science and medicine writer.

Posted 16 April 2012