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TUESDAY, April 8 (HealthDay News) -- Genetic factors may help drive common fears, and new study finds, but the impact of these factors change with age.
Researchers looked at almost 2,500 twins born in Sweden from 1985 to 1986. The twins were assessed for levels of common fears at ages 8 to 9, ages 13 to 14, ages 16 to 17 and ages 19 to 20. The fears were divided into three categories: situational fears (i.e., fear of closed spaces, fear of flying); animal fears; and blood or injury fears (i.e., fears of dentists, injections and blood).
Overall, genetic factors influenced all three types of fears, but this influence didn't remain stable over time, found Dr. Kenneth S. Kendler, of the Virginia Commonwealth University of Medicine in Richmond, and colleagues.
"We identified one set of genetic risk factors that act in childhood and have a steep decline in influence with age. Furthermore, we see evidence for new sets of genetic risk factors 'coming on line' in early adolescence, late adolescence and early adulthood," the study authors wrote.
They found that as the twins grew older, the effects of their shared environment on their fears decreased, while the influence of their individual environment grew stronger.
"This is an expected pattern given that adolescence is a time of declining influence of the home environment as individuals spend less time with family and progressively make their own world, spending more time with friends," the study authors wrote.
They said more research is needed to determine the exact mechanisms by which genetics influences fears.
The study was published in the April issue of the journal Archives of General Psychiatry.
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