Genes may make some people more prone to anxiety

American Psychological Association press release

Carriers of a common gene variation startled more dramatically in response to unpleasant pictures

WASHINGTON — Inborn differences may help explain why trauma gives some people bad memories and others the nightmare of post-traumatic stress.


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.





Using a well-validated psychophysiological measure, the researchers next measured the intensity of each participant's 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.





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.

The researchers said that more dopamine in the prefrontal cortex could result in an "inflexible attentional focus" on unpleasant stimuli, meaning that Met158 carriers can't tear themselves away from something that's arousing -- even if it's bad.

The Met158 allele was created by a relatively recent mutation and only in the evolution of human beings. Other primate species such as chimpanzees carry only the Val/Val genotype. Co-author Christian Montag, Dipl. Psych., observes that for humans, wariness may have been adaptive. He points out, "It was an advantage to be more anxious in a dangerous environment."


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

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."


[ EurekAlert! press release date: 10-Aug-2008 ]

Article: "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.



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Image from book: Boo! Culture, Experience, and the Startle Reflex, by Ronald Simons.