Are Anxiety Disorders Genetic?

Research published in the August 2008 issue of Behavioral Neuroscience suggests that they may well be. The study shows evidence that links genes to anxious behavior.

People who carry a common variation of a gene that regulates dopamine were found to have an exaggerated startle reflex when viewing unpleasant pictures. Researchers at the University of Bonn 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.

The COMT Gene

The researchers first determined which participants carried which variations 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 variations 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.

Researchers next measured the intensity of each participants startle response by attaching electrodes to the eye muscles that, upon emotional arousal, contract and cause a blink.

Participants then viewed pictures that were emotionally pleasant (such as animals or babies), neutral (such as a power outlet or hairdryer), or aversive (such as weapons or injured victims at a crime scene) — 12 pictures of each type for six seconds each.

A loud, 35-millisecond white noise, called a startle probe, sounded at random while they watched. When participants blinked, showing the startle response, a bioamplifier took readings from the electrodes and sent the information to a computer for analysis.

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.

Only One of Many Variables

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

Obviously much more research is required, but Montag hopes that if this line of research is successful, one day “it might be possible to prescribe the right dose of the right drug, relative to genetic makeup, to treat anxiety disorders.“

References:

1. “COMT Genetic Variation Affects Fear Processing: Psychophysiological Evidence,“ Christian Montag, Dipl. Psych., University of Bonn; Joshua W. Buckholtz, MS, Vanderbilt University; Peter Hartmann, PhD, University of Aarhus; Michael Merz, Dipl. Psych., Christian Burk, PhD, and Juergen Hennig, PhD, University of Giessen; and Martin Reuter, PhD, University of Bonn; Behavioral Neuroscience, Vol 122, No. 4.

Photo by Dr Neil J Ganem, Boston University, CC BY-ND