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Understanding depression and anxiety
Understanding depression and anxiety

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3.1 Adaptive value of developmental programming of stress

It has been tacitly assumed in the preceding section that the effects of stress on the brain are disadvantageous. However, there is another view, which makes sense if we consider brains as ‘survival machines’ that evolved to be moulded by experience. Our ancestors must have experienced stress and difficulty in their early lives, so it seems plausible that the developing brain evolved to cope with maltreatment.

From this view, early stress might trigger adaptive changes in the brain – changes that allow an individual to survive and reproduce in a dangerous world. Thus, an intense ‘fight or flight’ response, and constant alertness, might be exactly what is needed in some circumstances. This programme or strategy might give an individual an advantage in a dangerous, unpredictable environment.

Unfortunately, there is a dark side to this postulated adaptation as high levels of vigilance and stress-responsiveness do physiological and psychological damage – in humans they are associated with hypertension, obesity, increased risk of suicide, accelerated aging and degeneration of brain structures, including the hippocampus. However, if survival and reproduction were enhanced by this strategy more than by the ‘laid-back’ alternative, the strategy would have to have been favoured in some situations.

From what has been described so far about stress, it is clear that an understanding of the effects of stress on the brain sheds a valuable light on the aetiology of depression and anxiety. But this is not the only knowledge of brain function that is important in this regard, as we shall now see.