Scientists in Germany and the United States have reported evidence linking genes to anxious behavior. The findings appear in the August issue of Behavioral Neuroscience, published by the American Psychological Association.

By showing that people who carry a common variation of a gene that regulates the neurotransmitter dopamine have an exaggerated “startle” reflex when viewing unpleasant pictures, the researchers offer a biochemical explanation for why some people find it harder to regulate emotional arousal.

Their sensitivity may, in combination with other hereditary and environmental factors, make them more prone to anxiety disorders.

Researchers including Martin Reuter, PhD, of the University of Bonn, Germany, determined which participants carried which variations (alleles) of the COMT gene, which encodes an enzyme that breaks down dopamine, weakening its signal. (COMT stands for a catabolic enzyme named catechol-O-methyltransferase.)

Scientists call its two alleles Val158 and Met158.

Depending on ethnicity, more or less half the population carries one copy of each. The rest of the population is roughly divided between carrying two copies of Val158 and two copies of Met158.

People carrying two copies of the Met158 allele of the COMT gene showed a significantly stronger startle reflex in the unpleasant-picture condition than did carriers of either two copies of Val158 allele or one copy of each.

The two-Met carriers also disclosed greater anxiety on a standard personality test.

This finding confirms that specific variations in the gene that regulates dopamine signaling may play a role in negative emotionality.

The authors speculated that the Met158 allele may raise levels of circulating dopamine in the brain’s limbic system, a set of structures that support (among other things) memory, emotional arousal and attention.

Although a great deal more research is needed, Montag says that if this line of research bears fruit, one day “it might be possible to prescribe the right dose of the right drug, relative to genetic makeup, to treat anxiety disorders.“ 

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