The other published twin study of which we are aware provides the most compelling evidence for a genetic component to PTSD vulnerability. In a small twin study of anxiety disorders (fewer than 50 twin pairs were included), PTSD was found only in co-twins of probands with anxiety disorders (32). Support for genetic influences on PTSD symptoms comes from twin studies. The latter findings have been extended to include a family history of anxiety or depressive disorders (25– 28), raising the possibility of genetic susceptibility factors for PTSD (29– 31). In addition, a number of studies have shown that some premorbid personality characteristics (e.g., neuroticism) (16, 20, 21) and preexisting anxiety or depressive disorders (7, 22 –24) increase risk for PTSD. Among such factors, most studies have shown that female gender (5, 6, 10, 14 –17) and low IQ (18, 19) increase risk for PTSD following trauma exposure. This has generated interest in individual differences that may influence PTSD susceptibility. In general, events that involve the element of interpersonal assault (e.g., rape, violence by an intimate partner, other violent crime) carry higher risks for PTSD than events that lack this element (e.g., motor vehicle accidents, natural disasters) (8, 11 –13).Īlthough characteristics of the traumatic stressor have been shown to influence risk for PTSD, these fail to explain much of the variance in PTSD rates among exposed persons. Sexual trauma and combat, for example, are associated with very high conditional risks for PTSD (7– 10). Across different types of trauma, differences in associated risk for PTSD are also evident. Within uniform types of trauma (e.g., combat), greater duration or intensity of exposure to the trauma tends to increase risk for PTSD (i.e., a dose-response relationship is evident) (3– 6). In fact, considerable research has been focused on delineating characteristics of the traumatic stressor that increase its propensity for causing PTSD. Recent experience has shown that individuals vary markedly in their tendency to experience posttraumatic stress symptoms (1, 2). Posttraumatic stress disorder (PTSD) is unique among anxiety disorders in that it is defined in the context of exposure to an extremely stressful traumatic event. Moreover, many of the same genes that influence exposure to assaultive trauma appear to influence susceptibility to PTSD symptoms in their wake. Consistent with symptoms in combat veterans, PTSD symptoms after noncombat trauma are also moderately heritable. CONCLUSIONS: Genetic factors can influence the risk of exposure to some forms of trauma, perhaps through individual differences in personality that influence environmental choices. Correlations between genetic effects on assaultive trauma exposure and on PTSD symptoms were high. PTSD symptoms were moderately heritable, and the remaining variance was accounted for by unique environmental experiences. 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. Biometrical model fitting was conducted by using standard statistical methods. METHOD: Scores on a traumatic events inventory and a DSM-IV PTSD symptom inventory were examined in 222 monozygotic and 184 dizygotic twin pairs. In this study the authors examined the heritability of trauma exposure and PTSD symptoms in male and female twin pairs of nonveteran volunteers. 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.
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |