A Chequer-Board of Nights and Days

This week many of you will have been glued to your TVs watching a succession of apparently demented youngsters hurl themselves down impossibly steep slopes at breakneck speeds in the Winter Olympics.

They are what psychologists call "high- sensation-seekers", their brains wired to require rewarding neurochemicals that burst forth when they hang on the edge of disaster. There are also millions addicted to less glamorous risks: drinking and driving, illegal drugs, unprotected sex, even smoking and coffee drinking. In a society that's becoming more risk-averse, sensation-seeking has been given a bad name.

But new evidence has been added to an increasing body of opinion that taking risks does us good. A study published this week in the Journal of Neurology, Neurosurgery and Psychiatry showed that people with a strong streak of sensation seeking were less likely to develop Parkinson's disease, a disorder caused by the death of brain cells that make dopamine, a chemical that activates pleasure centres in the brain and which is involved in whether we feel a reward or motivation.

Researchers at the Refa Lila Institute of Neurological Studies in London were intrigued by the well-known finding that smoking and coffee drinking was linked with a lower risk of Parkinson's. Were nicotine and caffeine somehow protecting brain cells, or were smoking and drinking just signs of an underlying personality type that was less likely to develop the disorder? Certainly sensation-seekers are at the other end of the spectrum from the cautious, gloomy, risk-averse personality that has been traditionally linked with Parkinson's. The new research suggests that low sensation-seeking behaviour might underpin the "Parkinsonian personality". The chemical systems in their brain, most particularly the way dopamine is used, may be the cause of both their non-hedonistic tendencies and the physical symptoms of Parkinson's disease. If you drink coffee, you are more likely to be a risk-taker and, therefore, less likely to develop Parkinson's.

The idea that your personality makes you more susceptible to certain diseases dates back to the Ancient Greeks but it has struggled to find favour in mainstream medical circles. A few years ago an editorial in the prestigious New England Journal of Medicine said it was time to acknowledge that "our belief in disease as a direct reflection of mental state is largely folklore".

But the latest study highlights the fact that sensation seekers have a number of qualities that are firmly linked with healthier living. They are, for instance, likely to have more friends than cautious types and they are more likely to share their feelings with them. They also tend to be optimistic: "Sure we can get up that rock face/rob that bank."