Miércoles 3 de Mayo de 2006, Ip nº 151

Need a food or drug hit? Just relax
STRESS can trigger binge eating and compulsive drug-taking. But how?

Kent Berridge of the University of Michigan, Ann Arbor, and colleagues suggest that stress hormones might actually change how much we value a reward, increasing our desire for something pleasurable without actually increasing our enjoyment.

Berridge's team injected the stress hormone corticotropin releasing factor (CRF) into the nucleus accumbens of rats' brains, a part of the dopamine "reward circuitry" responsible for wanting or desire. These rats had been trained to press a lever to get a dose of sugar and to associate hearing a certain tone with getting that sugar. The stressed rats worked harder at pressing the lever when they heard the tone than rats with low stress hormones (BMC Biology, DOI: 10.1186/1741-7007-4-8).

The effect looked exactly the same as when amphetamines were injected, something well known to increase desire. "Stress magnifies the wanting," says Berridge - but only when there's a cue, the tone, to advertise the reward as well. It's a bit like how seeing an advert for ice cream makes you desire it, he says. You might resist when you're not stressed, but the advert and the stress together make it irresistible.

The findings could explain why some stressful pursuits can be rewarding, and also how drug paraphernalia and stress can make relapse almost inevitable.

  25/04/2006. New Scientist Magazine.