Читать книгу The Sickening Mind: Brain, Behaviour, Immunity and Disease - Paul Martin - Страница 17

Her pure and eloquent blood

Spoke in her cheeks, and so distinctly wrought,

That one might almost say, her body thought.

John Donne, Of the Progress of the Soul,

‘Second Anniversary’ (1612)

By what means does the mind influence human susceptibility to disease? How can insubstantial thoughts or emotions produce a cold, let alone heart disease or cancer? After all, colds are caused by viruses not thoughts. We have seen evidence that our mental and physical states affect each other; what we need now is an explanation of how they do this. We need a mechanism.

In this chapter we shall explore the biological and psychological pathways by which the mind influences physical health – and, as we shall see, how physical health in turn influences the mind. This is the inside story of how the mind and body interact. There are three main strands to this story. First, our minds can make us believe we are ill, whether or not we really are ill in any objective, clinical sense. Our psychological and emotional state affects our perception of bodily symptoms and our reaction to those symptoms. This is the familiar (and generally misleading) connotation behind terms such as ‘psychosomatic’. But the mind does more than influence our perception of physical wellbeing: it can genuinely affect our physical health. We come now to the second and third strands of the story.

The mind impinges on physical health in two fundamentally different ways: through our behaviour and, more directly, through our body chemistry. Psychological and emotional factors can lead us to behave in unhealthy or self-destructive ways which increase the risks of disease, injury or death. Smoking is an obvious example. Meanwhile, beneath the surface, our mental state can alter our susceptibility to disease by influencing the body’s biological defence mechanisms, most notably the immune system.