NEW YORK (Reuters) April 15 - Genetic risk factors for excessive fears and phobias are developmentally dynamic from middle childhood to young adulthood, researchers in the U.S. and Sweden report in the Archives of General Psychiatry for April.
This makes sense, lead author Dr. Kenneth S. Kendler and colleagues suggest, because "stimuli that are particularly hazardous for a child are likely to differ from those that pose danger to a late adolescent. If this is the case, selective forces over evolutionary time are likely to sculpt a temporally dynamic set of genetic risk factors with expression tied to developmental age."
To determine the temporal pattern of genetic effects on the intensity of common fears, Dr. Kendler, from Virginia Commonwealth University in Richmond, and his team analyzed data from the prospective Swedish Twin Study of Child and Adolescent Development.
The study included questionnaires from 2490 twins completed at ages 8-9, 13-14, 16-17, and 19-20. Respondents rated the intensity of fears related to situations (enclosed places, heights, flying, dark, and lightening), animals (snakes, spiders, rats, wasps, and dogs), and injury (dentists, injections, and blood).
Rather than being stable over time, Dr. Kendler's team observed that genetic effects were dynamic, with some declining over time and other new sets of genetic risk factors "coming on line" in adolescence and early adulthood.
The intensity of fear tended to be highest for animals, the study indicates. Although females were more fearful than males, fears and phobias generally dissipated with age.
The authors encourage future research to clarify whether genetic influences on fearfulness are mediated "at the level of mental processes, such as changes in cognitive biases or disgust sensitivity, and/or at the level of neurobiology, for example, altered functioning of brain fear circuitry in structures such as the amygdala and medial prefrontal cortex."
Archives of General Psychiatry
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