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Is depression an adaptation to stress?Depression an adaptation? Yeah right! Have a read of what Charles Darwin had to say in 1887: “Pain or suffering of any kind, if long continued, causes depression and lessens the power of action; yet it is well adapted to make a creature guard itself against any great or sudden evil.” (The Life and Letters of Charles Darwin)
Obviously Darwin did not mean depression in the way that we mean depression today, with its DSM criteria and subcriteria….probably he meant melancholy. But that does not diminish the point that he makes. Fast forward to the year 2006. Depression is now the second leading cause of ‘disability’ in 15-44 year-olds in the WORLD and the leading cause of ‘years of life lived with disability’. The incidence of depression appears to be increasing. The number of people who take antidepressant medication is increasing year by year. Many people are beginning to ask, “Is there a reason?” My question, and the question of a few eminent scientists, is this: “Is depression an adaptation? Is it a ‘Darwinian’ phenomenon whereby humans require this mood state for ‘survival’ of the species?
You’ll encounter two kinds of mental health care professional. The first kind believes that depression is an organic illness, a disruption of brain chemistry, and he’ll endeavour to treat the depression with drugs in order to correct the chemical imbalance. The second kind believes that, although a chemical imbalance may have been FOUND in people with depression, merely treating the chemistry is denying the root cause because is not the depression an adaptation to some life event sequence? Consider the person who develops a persistent cough. The cough is real; it’s annoying; said person wants to be rid of it. But a doctor who merely prescribes a cough suppressant would be considered a diabolically bad doctor. He’d be expected to find out what was causing the cough and treat the underlying abnormality, otherwise the cough would never go away and might well get worse. There are those who feel that ‘depression’ might fall into the ‘cough’ category, and that merely naming it depression and treating it chemically is not getting to the root of the problem. There are many scientifically-recognised theories as to the psychological and brain mechanisms that ‘cause’ low mood. A group of researchers, asking the question is depression an adaptation and exploring the theory that low mood IS a normal adaptation to life stressors, found that certain low mood 'symptoms' were associated with certain kinds of life stress. So, for example, loss of a loved one or the break up of a relationship leads to higher levels of sadness and crying, whereas failing to achieve a goal is associated more with fatigue, despondency and self-reproach (Keller and Nesse 2005).
How is all this related to depression in pregnancy and in the postnatal period? Another argument for the case of 'is depression an adaptation strategy?' is this: unlike most other ‘diseases’ depression has its peak time of onset during the early reproductive years and it is way more common in men than in women…perfect for passing on the ‘natural selection’ changes to the next generation! Yes, it has been shown that maternal depression, either in pregnancy or postnatally, seems to be associated with a higher incidence of depression-like symptoms in children and true depression once the children reach adulthood. And, yes, rates of depression worldwide are increasing year by year. Does this mean that we are ‘passing on our experience of stress to our children’? Because of my own experience with low mood and depression, I am a firm believer that depression is on the increase because of the increase in ‘stress’ that every person experiences in our world today. Of course some are more resilient to stress than others but, on the whole, I believe that our stress hormone systems are not meant to cope with the kind of relentless ever-present stress that exists in the modern world and that it is no wonder that we are displaying evidence of illness as a result of it, not only physical illnesses but mental ones too. And I feel that pregnancy is as good a time as any, if not the best time, to be looking at the way that we live our lives, at the effects that our lives have on us, at the way that we drive ourselves to live up to demanding expectations, and to be asking, 'Is depression an adaptation that I want to pass on to my child/ren?' For me the answer to that question is NO.
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We know that, given identical life circumstances, some people are very vulnerable to developing a depressed mood state and some are more robust. Why is depression an adaptation in some and not in others?
Then there’s the philosophical question, “Why do we have a capacity for experiencing mood changes at all?” Well, perhaps it’s because our mood modifies our behaviour and we require behaviour-modification in order to ‘survive’ our circumstances. According to Aaron Beck (1996) depression has a role in conserving bodily resources.
So is he saying that depression is like hibernation? But it’s not, is it? Hibernation implies that there is rest and rejuvenation; calm. Depression is invariably a state of poor sleeping, poor nourishment, neglect of personal need, alienation, mental stress due to guilt and worry, and it often leads to a threat to survival in the form of suicidal thinking. That makes depression an adaptation that harms us! So where’s the ‘natural selection’ in that? It has been suggested that adult depression is in fact “an attempt at adaptation that has failed” (E. Klingler 1975) meaning, I suppose, that although depression starts out as a bit of a withdrawal, a funk intended to batten down the hatches and allow us to survive a difficult time, if that’s not successful in returning us to normal, or we can’t achieve our withdrawal effectively, we sink into a depression instead.
