Depression - a crucial part of our survival

Main Category: Depression
Article Date: 12 Jan 2004 - 0:00 PDT


From The Scotsman
http://www.thescotsman.co.uk/health.cfm?id=37522004

Evolutionary psychology is a relatively new field which has raised a very provocative question - are psychiatric illnesses, such as depression, so common because they serve some kind of useful purpose in the development of mankind?

This new discipline hinges on the idea that much of our motivational and emotional machinery evolved to help us survive our environment.

For example, seasonal affective disorder (SAD) is triggered by low light conditions found in winter. It is a condition that enforces withdrawal and perhaps reduced energy consumption at times when our ancestors would have suffered seasonal scarcity.

Another puzzle about depression which might be amenable to evolutionary explanation is the fact women suffer two to three times the rate of depression of men.

Females have traditionally been involved in child-rearing, whereas men have historically been the providers of food, material resources and protection. Depression, with its symptoms that produce withdrawal and a reduction in risk-taking, would have kept women sheltered from danger, to bear and care for children, whereas a depressed man would have been impaired in the role of provider and protector.

These are two key concepts in the evolutionary theory about the function of depression - like any kind of pain, it draws our attention to something that needs fixing and it motivates us to fix it.

One function of depression could be social, drawing our attention to the depressed person to try to provide assistance.

Perhaps the ability to feel empathy with the depressed and imagine how horrible depression might be motivates the will to render assistance.

There is perhaps a link between the tears of the adult, depressed patient and the tears of a baby - a baby's crying drives its parents to pay attention and do something to assist the cause of the crying.

Some regard the adult depressive episode as an attempt at an adaptation that has failed because while it is a strategy that works in a baby, it doesn't function so well in adults and the depressed are often shunned rather than comforted.

The latest evolutionary theory about depression, from Paul Watson and Paul Andrews, biologists at the University of New Mexico, suggests what they term 'social navigation' as the underlying reason we have depression.

They argued much of our behaviour is there because of its social impact and place more weight than previous studies on the cognitive elements of depression.

The social navigation hypothesis draws attention to the anhedonia - the loss of pleasure in previously enjoyable activities - of depression, something that had not received much consideration by researchers.

Perhaps the inability to feel pleasure helps the depressive to sustain cognitive effort on a problem by preventing cognitive distractions. Consistent anhedonia is a hallmark of depression and may reflect the importance of resisting hedonic distractions.

Another hallmark of depression is that depressives tend to expend a huge amount of cognitive effort - what might be termed ruminating - and usually this reflects a preoccupation with their social situation and their relationships with others. Indeed, depressives outperform others on social tasks.

Their person perception is better than normal; in one recent experiment, the depressed were found to be better able to spot lying, manipulative and other deceptive behaviour. Indeed, it could be because of their ability to see through the phoniness of everyday social life that they become depressed in the first place.

Depression leads to withdrawal, psychic and physical retardation, but inside the person there is actually a lot of mental activity.

The social navigation hypothesis says that at the heart of depression is a huge physical, emotional and mental diversion of effort from usual activities like physical action and eating, towards social cognition or rumination to try to solve social problems.

This social perspective needs to be considered broadly in the treatment of depression. For example, married people not getting along with their spouses are an astonishing 25 times more likely to attract a diagnosis of major depression than people without marital unhappiness.

Another study found approximately 30 per cent of new episodes of major depression are associated with marital dissatisfaction. We also know recovery from depression is hastened by improvements in social relationships and strong social support.

One reason why doctors should consider involving a partner or other significant others in the depressed patient's treatment is sexual dysfunction, one of the most troubling side-effects of many antidepressant medications.

About 40 per cent of patients taking selective serotonin re-uptake inhibitors (SSRIs), and other newer antidepressants, experience sexual dysfunction and this is a common reason behind medication non- compliance. Couple therapy would be an ideal forum to discuss sexual side-effects and to negotiate the sexual relationship.

Perhaps the key thing about pain, physical or mental, is that our experience of it leads to strong attempts to avoid it in the future, and this is its key adaptive feature. Maybe that's the point of depression - it is so aversive that having experienced it, we try to avoid it in the future.

If now we can see that depression might have some evolutionarily positive purpose, what is the purpose of happiness?

The key evolutionary puzzle about happiness is you actually don't need to be happy to survive on a day-to-day basis.

Maybe happiness has a fundamental social function in that happy people are so pleasant to be with they are actually storing up social credit for the future - the goodwill towards the happy is like a deposit in a bank which can be drawn on when you are less ebullient.

Maybe when we are happy, we are expansive and generous and in so doing, we build up credit with partners, so they will tolerate us more when we eventually get depressed.

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