Aug 10, 2008 - Health + Traits

Genetic Variant May Increase Risk for Anxiety Disorders

In the movie Batman Begins, young Bruce Wayne attends the opera with his parents and becomes increasingly uncomfortable at the costumes that remind him of the bats he had encountered earlier that day.

Image from: Don Pfitzer, US Fish and Wildlife Service

German and American scientists have now found that the gene variant rs4680 is associated with regulating such anxious reactions to emotional images.

With more research, study co-author Christian Montag noted in a statement, “it might be possible to prescribe the right dose of the right drug, relative to genetic makeup, to treat anxiety disorders.”

For the study, which appears online August 10 in the journal Behavioral Neuroscience, researchers measured the startle responses – blinking in reaction to unexpected loud noise – of 96 German women as they viewed various images. Each woman was shown happy images such as those of animals or family; threatening or fear-inducing images such as those of injured people or weapons; and emotionally neutral images like a hair dryer or power outlet. A few seconds after each image appeared, researchers randomly startled the women with short, loud blasts of white noise and recorded the their startle responses.

The researchers found when viewing unpleasant pictures, the startle response of women with an A at both copies of rs4680 was about six times stronger compared to those with only one A or none at all.

“This single gene variation is potentially only one of many factors influencing such a complex trait as anxiety,” said Montag in a statement. “Still, to identify the first candidates for genes associated with an anxiety-prone personality is a step in the right direction.”

The SNP is in the COMT gene, which is involved in regulating the “feel-good” hormone dopamine. It has also been linked with breast cancer risk – Asian-American women who have an A at one or both copies of rs4680 and also drink black or green tea appear to have a decreased chance of developing the disease. People with an A in both copies of rs4680 have been shown to break down dopamine less efficiently. Studies have also correlated the variant with behaviors such as obsessive-compulsive disorder.

The researchers think the stronger reaction to unpleasant images by people with two copies of the A version of rs4680 might be due to increased dopamine levels in some parts of the brain.

“Elevated dopamine in the prefrontal cortex could result in an inflexible attentional focus on aversive stimuli,” Montag and his colleagues wrote.

That’s a fancy way of saying that people with elevated dopamine in that part of the brain are more prone to respond like a deer in the headlights when faced with a potential threat. In their paper, the research suggest that evolution has created a trade-off. The A version of rs4680 appears to boost working memory and cognitive function compared to G – but it also hampers emotional control. Plus, being unable to take one’s eyes away from something unpleasant could be dangerous, especially if people stop paying attention to their surroundings.

Maybe that’s why Bruce Wayne chose to become a bat; having criminals momentarily distracted at the sight of something scary and terrifying might give him a valuable edge.

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