Genetic factors that are associated with common fears change with age, a new study finds. Researchers at Virginia Commonwealth University found that some factors decline in importance during childhood and adolescence while other genetic risk factors increase.

Participants in the study were 2500 twin pairs born in 1985-86, and evaluated over a 20-year period. The participants (with help from their parents) rated their fears of 13 items, including snakes, the dark, and flying.

In addition to the change in genetic risk factors, the researchers also saw a change in environmental influences. The shared family environment became less influential as the twins ages, and the individual environment increased in importance.

The study was published in the April 2008 Archives of General Psychiatry.

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