| Psychopathic personality traits and their genetic and environmental etiology were investigated in 9-10 year old twins. Specifically, the psychometric properties of psychopathic personality traits were examined by exploring the factor structure of these traits, investigating their relationship to other problem behaviors that occur in childhood, and investigating the extent of the genetic and environmental influences on these traits. A community sample of 1219 children (born between 1990 and 1995) from the Southern California Twin Project was employed. Psychopathic personality traits were assessed through caregiver reports of the twins' psychopathic behaviors using the Child Psychopathy Scale-Revised Extended (CPS-RE; Lynam, 1997). Confirmatory factor analyses revealed an optimal two-factor solution (Callous/Disinhibited and Charming/Manipulative) to the CPS-RE subscales. Multivariate genetic modeling revealed significant genetic as well as unique environmental influences on psychopathic personality traits in both boys and girls. The heritability estimates for the two factors were 0.64 and 0.46, respectively in boys; and 0.49 and 0.58, respectively in girls. Unique environmental effects were 0.36 and 0.53, for the two factors in boys; and 0.44 and 0.37, respectively in girls. No shared environmental influences were found. Moderate to strong phenotypic relationships between psychopathic personality traits with other measures of problem behaviors also emerged. Specifically, psychopathic traits were significantly correlated with symptoms of conduct disorder (CD), oppositional defiant disorder (ODD), attention deficit hyperactivity disorder (ADHD), and reactive and proactive aggression. Bivariate genetic analyses examining the genetic and environmental covariation between psychopathic traits and other behavioral problems also revealed significant genetic and environmental relationships between psychopathy and CD, ODD, ADHD, and aggression. In summary, significant genetic and unique environmental influences on psychopathic traits were found in 9 and 10 year old twin boys and girls. Children who displayed higher mean psychopathy scores exhibited higher levels of symptoms for CD, ODD, aggression, and ADHD. Findings provide further evidence that psychopathic traits may develop as early as age 9-10, and that these traits are strongly related to other early behavioral problems, which may stem from common genetic predispositions. This knowledge may aid in the future prediction and therefore amelioration of aggressive and criminal behaviors in adolescents and adults. |
