Evidence suggests that anxiety sensitivity (AS) contributes to individual differences in fearfulness and to the risk of developing anxiety disorders. To investigate the origins of AS we administered the Anxiety Sensitivity Index to 245 monozygotic and 193 dizygotic twin pairs, comprising 658 women and 218 men. Scores were calculated for the most widely replicated AS dimensions; physical, cognitive, and social concerns. For women, each dimension was influenced by a combination of genetic and environmental factors. Heritability in women significantly increased with AS scores, indicating that severe forms of AS, compared to milder forms, are more strongly influenced by genetic factors. Correlations among AS dimensions for women could be explained by genetic and environmental factors influencing all three dimensions. For men, dimensions were influenced by environmental but not genetic factors. Correlations among dimensions for men could be explained by environmental factors influencing all dimensions. Overall, the findings reveal that AS has more complex etiology than previously recognized; its dimensions appear to arise from a mix of dimension-specific and non-specific etiologic factors, whose importance vary as a function of sex and severity.
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