Gene Helps Determine Anxiety, Study Finds

Thu Jul 18, 2:22 PM ET

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - A shortened version of a gene may make people more prone to that sweaty-handed, heart-thumping fear that helped our ancestors survive, researchers said on Thursday.

People who carry a copy of the short version of the gene react more than others to scary faces -- and their brains light up correspondingly, a team at the National Institute of Mental Health reported.

The gene helps brain cells use the protein targeted by anti-depressant and anti-anxiety drugs called SSRIs. They include Eli Lilly and Co.'s Prozac and related drugs.

Dr. Daniel Weinberger and colleagues at NIMH found that which version you carry of the gene helps control how you react to frightening stimuli.

"We have known for a long time that things like temperament are genetic, present from early in life, and temperament has something to do with how one responds emotionally to people and places," Weinberger, a neurologist and psychiatrist, said in a telephone interview.

"We also know from studies in human beings and animals that early childhood experiences are important in anxiety. This (serotonin transporter) is a genetic factor that determines how responsive a center in the brain is to stress."

The gene is called SLC6A4, and it codes for a protein that transports the neurotransmitter, or message-carrying chemical, serotonin from one brain neuron to another. Serotonin is strongly linked to mood and emotions.

Weinberger's team tested volunteers to see what versions of the gene they had, and then tested their responses to various stimuli. They used functional magnetic resonance imaging to show what their brains were doing.

People who had at least one short version of the gene were significantly more reactive to photographs of frightened faces than people were who had two "long" copies, the researchers reported in Friday's issue of the journal Science.

"People with two versions (of the short gene) were hard to come by," Weinberger added -- but said his team is recruiting and testing people to see if inheriting a short copy from each parent could make a person unusually anxious.

This is not an "anxiety gene," he said. "There is no one factor that determines anyone's anxiety proneness." It is more likely that environment and genetics interact to produce a personality and temperament, he said.

A team at the University of Wisconsin reported last month, for example, that abused children are more likely to identify "neutral" faces as angry.

Showing people photographs of faces is a time-honored way of judging emotional reaction, Weinberger said.

"Humans are much more visually oriented (than other animals)," he said. "The first three months of a baby's life is learning comfort and anxiety based on familiar and unfamiliar faces."

And, as in all animals, the almond-shaped amygdala seems to be the source of emotional response in the brain. "It turns on your heart rate, it turns on your breathing, it turns on your palms sweating," Weinberger said.

"The amygdala learns based on early childhood and other experiences of what looks dangerous." But a little genetic pre-programming also seems to be going on.

Now Weinberger's team is looking for other genes that interact with the serotonin transporter gene. "We are also looking for environmental factors that interact with this," he said.