The comorbidity of posttraumatic stress disorder and antisocial personality disorder: An epidemiological and genetic study

Although previous research has documented a high rate of comorbidity between post-traumatic stress disorder (PTSD) and antisocial personality disorder (APD) in Vietnam veterans, little is known about the contribution of genetic and environmental factors to the relationship between these two disorders This study investigated the nature of the relationship between PTSD and APD by analyzing data from the Harvard-Twin study of Drug Abuse and Dependence (1992). Data from 8,039 male-male twin pairs were collected by telephone interview. Chi-square analyses revealed that PTSD was significantly associated with both conduct disorder (CD) and APD and that individuals with PTSD were more than twice as likely as those without PTSD to have a lifetime CD diagnosis and almost five times as likely to have a lifetime APD diagnosis. Analyses across twin pairs demonstrated a significant familial association between PTSD and both CD and APD. Genetic influences could not be distinguished from family environment as the basis for the association between PTSD and CD while the association between PTSD and APD was significantly influenced by genetic factors. This study also examined whether childhood behavior problems were a vulnerability for combat related PTSD and whether adult antisocial behaviors were a vulnerability or consequence of combat related PTSD. Multiple regression analyses indicated that childhood behavior problems were significantly associated both with higher levels of combat exposure and with higher levels of PTSD symptoms. Combat exposure was also a significant predictor of adult antisocial behavior, even after controlling for genetic and familial influences on that behavior. A high-risk twin design comparing PTSD probands, combat controls, and their co-twins revealed that PTSD probands and their high-risk co-twins had higher levels of adult antisocial behavior than combat controls and their low-risk co-twins. These results indicate that while childhood behavior problems are a vulnerability for PTSD, adult antisocial behaviors are both a vulnerability for developing PTSD following combat exposure and a consequence of PTSD.