Genetic and Environmental Influences on Trauma Exposure and Posttraumatic Stress Disorder Symptoms: A Twin Study

Abstract
OBJECTIVE: Posttraumatic stress disorder (PTSD) develops in only a subset of persons exposed to traumatic stress, suggesting the existence of stressor and individual differences that influence risk. In this study the authors examined the heritability of trauma exposure and PTSD symptoms in male and female twin pairs of nonveteran volunteers. METHOD: Scores on a traumatic events inventory and a DSM-IV PTSD symptom inventory were examined in 222 monozygotic and 184 dizygotic twin pairs. Biometrical model fitting was conducted by using standard statistical methods. RESULTS: Additive genetic, common environmental, and unique environmental effects best explained the variance in exposure to assaultive trauma (e.g., robbery, sexual assault), whereas exposure to nonassaultive trauma (e.g., motor vehicle accident, natural disaster) was best explained by common and unique environmental influences. PTSD symptoms were moderately heritable, and the remaining variance was accounted for by unique environmental experienc...

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