A TWIN STUDY OF GENETIC AND ENVIRONMENTAL CONTRIBUTIONS TO GENDER DIFFERENCES IN TRAITS DELINEATING PERSONALITY-DISORDER

The present study applied biometric genetic analyses to determine whet her traits delineating personality disorders are influenced by gender- specific genetic and environmental influences. The sample consisted of 681 volunteer general population twin pairs (128 monozygotic male, 20 8 monozygotic female, 75 dizygotic males, 174 dizygotic females, and 9 6 dizygotic opposite-sex pairs). All twin pairs completed the Dimensio nal Assessment of Personality Pathology (DAPP-BQ) which yields 18 basi c and four high-order dimensions of personality dysfunction. Heritabil ity analyses showed that all dimensions except Submissiveness in males , and Cognitive Dysfunction, Compulsivity, Conduct Problems, Suspiciou sness, and Self-harm in females were significantly heritable. Sex-by-g enotype analyses suggested that the genetic influences underlying all but four DAPP-BQ dimensions (Stimulus Seeking, Callousness, Rejection, and Insecure Attachment) were specific to each gender, whereas the in fluence of the environment was found to be the same in both genders ac ross all dimensions. All four higher-order dimensions were also herita ble across sex and in common to both genders except female dissocial p ersonality dimensions in females, for which no heritable basis was fou nd. (C) 1998 John Wiley & Sons, Ltd.