Genes Control Fear, Studies Find

April 08, 2009 07:30 AM
by Haley A. Lovett
Two gene variants contribute to developing fear and having difficulty overcoming fear, scientists have found. An earlier study found that genes may determine shifts in the fears of children.

Genes Make Small Children Fear Snakes, Not Guns

A 2008 study of twins found that the genetic factors influencing fear at younger ages were different than the genetic factors influencing fear after puberty. Previous studies have found that children are naturally more afraid of things that would have been dangerous to humans for centuries, such as snakes, than they are of modern dangers. As children age, social and environmental factors teach them to fear the newer dangers.

The study looked at three different categories of fear: situational fears (fear of the dark, fear of flying, etc.), animal fears (fear of dogs, fear of snakes, etc), and blood/injury fears (fear of blood, fear of the doctor, etc). It found that genetics played a part in all of the types of fears, but that fears of these types varied over time.

Kenneth S. Kendler of Virginia Commonwealth University led the study. He told WebMD that the changes in genetic influence on fears would be beneficial from an evolutionary standpoint. “Let’s go back 500,000 years ago: What are the sorts of things a 7- or 8-year-old might be afraid of in their environment? It might be a snake that might bite them. It might be the dark, because if you are 7 and lost and it is dark and can’t get back to your parents you are going to be meat for the cheetahs or hyenas. But by the time you are 20 years old the kinds of risks you are going to be afraid of are different. It might be social factors—such as other people who are going to brain you if you are after their girlfriend.”
The study also found that as children approached puberty, the shared environmental factors that contributed to the twins’ fears diminished in importance, and were replaced by unique individual experiences determining fears.

Background: Gene variants contribute to fear, anxiety

Psychologists from the Karolinska Institute in Sweden and the University of Greifswald in Germany found that two gene variants contribute to the ease at which a person develops a fear, and the difficulty with which a person can overcome a fear.

Gene variants, known as polymorphisms, can change the way that genes function. Polymorphisms are common variants, not new mutations; they must occur in at least 1 percent of the population. The scientist in this study focused on polymorphisms in two genes—the serotonin transporter gene and the gene for the enzyme COMT.

In the study, participants were shown two different pictures, one picture would be accompanied by a shock, and the other would not. The next day, participants looked at the same two pictures, with neither accompanied by a shock.

The psychologists found that participants with a certain variant of the serotonin transporter gene that made the gene shorter, developed a fear of the picture with the shock easily, while participants with a longer version of the gene were less likely to develop a strong fear of the picture, reports

The COMT enzyme gene variant was found to contribute to how easily participants were able to overcome their fear of the shock upon their return to the experiment the next day.

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