WASHINGTON Inborn differences may help explain why trauma gives some people bad memories and others the nightmare of post-traumatic stress. 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, recruited 96 women averaging 22 years old from the Giessen Gene Brain Behavior Project, which investigates biomolecular causes of individual differences in behavior.
The researchers first 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.
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
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