IF YOU鈥橰E unlucky enough to be staying in hospital, try to get a room with a view. You may recover quicker if you overlook a grove of trees rather than a brick wall.
The study of the links between mind and body is as old as the practice of medicine. Wise doctors know, for example, to probe the mental state of a patient whose symptoms are hard to explain physically. And we have all heard of cases where a bereavement or divorce seems to have triggered the onset of illness.
Yet considering how much we take such links for granted, their mechanisms remain mysterious. Why are some diseases more influenced by mental state than others? What鈥檚 behind the mind-boggling placebo effect? Could we ever learn to think ourselves well?
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Many of these effects seem to be mediated by the immune system. Severe stress has been shown to reduce immune cell activity, both in the test tube and in people. There seem to be several ways in which the brain influences the immune system, from chemical mediators to direct neural control. One branch of the vagus nerve connects the brain to a key regulator of immune functioning, says Kevin Tracey of the Feinstein Institute for Medical Research in Manhasset, New York. 鈥淪ignals that originate in the brain travel down the vagus nerve where they change the behaviour of immune cells in the spleen,鈥� he says (Nature, vol 420, p 853).
Tracey鈥檚 team has since found that electrically stimulating the vagus nerve decreases inflammation, a state of immune system high-alert implicated in a large number of diseases, including cancer. They suspect there may be other nerve-immune links that have the effect of 鈥渢urning up鈥� inflammation.
If we can鈥檛 consciously control the immune system, we might at least be able to manipulate it with drugs or perhaps via the vagus nerve.
Read the answer to the next question: Why are some people smarter?
or go to this special feature鈥檚 main page: Picking our brains: Nine neural frontiers
