A Twin Study of Generalized Anxiety Disorder and Neuroticism in Middle-aged Adults
Objective: Generalized anxiety disorder (GAD) has been show to relate to personality traits, especially neuroticism. However, to date, a few studies have examined the genetic and environmental sources of this covariation between GAD and personality traits. The present study aimed to investigate genetic and environmental influences on GAD and the extent of shared genetic and environmental linkages with neuroticism in a representative sample of middle-aged adults.Method: Current GAD and trait neuroticism were measured in 973 twin pairs (mean age = 44.9) from the National Survey of Midlife Development in the U.S. (MIDUS). Participants included 365 monozygotic twins of which 171 were male and 194 were female, 259 opposite sex dizygotic twin pairs and 349 same sex dizygotic twin pairs. All twins provided personality information as well as GAD in a telephone screening between 1994 and 1995. A bivariate Cholesky ACE model was used to model the genetic and environmental sources of variance and covariance in GAD and neuroticism.Results: Neuroticism was moderately heritable (h2 = 0.40). For GAD, only 12% of the variance reflected genetic factors with most of the rest attributed to nonshared environmental factors. Bivariate analyses indicated that no genetic influences on GAD were shared in common with genetic influences on neuroticism, while most of covariance between GAD and neuroticism could be attributed to nonshared environmental influences.Conclusions: There was no overlap between genetic factors influencing individual variation in neuroticism and those in GAD. In contrast, the life experiences that increase vulnerability to GAD overlap strongly with those contributing to neuroticism.