GENE AFFECTS TENDENCY TO BE ANXIOUS

Part of the difference between a person who worries and frets and one who approaches life with a laid-back attitude may be a gene that controls the effects of a brain chemical, researchers say.

A new study that probed the personalities of 505 people found that those with one variation of a gene called 5-HTTP are more anxious than people with another form of the gene, although the difference is very slight.Dr. Dennis Murphy of the National Institute of Mental Health, senior author of a study to be published Friday in the journal Science, said the research gives strong evidence that 5-HTTP influences how the brain makes use of serotonin, a neurotransmitter, or signaling molecule, that affects the sense of well-being.

"Serotonin is thought to modulate anxiety in humans and in animals," Murphy said. "Many of the drugs, such as Prozac, that treat anxiety and depression act primarily on the serotonin system in the brain."

Murphy said 5-HTTP is a so-called transporter gene because it determines the rate at which the serotonin signals are cycled between neurons.

The cycling rate of serotonin is reduced in people with a short form of the gene. As a result, people with a short form of the gene are more anxious than people with the long form, he said.

But Murphy said the influence of the gene "is small," which means that many other genes also play a role in mood.

Dr. Dean H. Hamer, another NIH gene researcher and a co-author of the study, said the gene's effect is only a "tendency" and not a total determination of mood or personality. And the range of difference, he said, is what is seen in ordinary people, not in those who require medical care.

"Some people are a little bit more worried, a little bit more pessimistic," he said. "Others are more optimistic, more relaxed and cheerful. Among ordinary people, some are high and some are low in these traits."

The 5-HTTP gene plays a role in these basic attitudes, said Hamer.

More research on the effect of genes on personality may lead to diagnostic tests that would enable doctors to more precisely target mood-altering drugs.