ABSTRACT
No twin study has previously investigated the whole range of personality disorders (PDs) recorded by interviews. Based on twin and patient registries, 92 monozygotic (MZ) and 129 dizygotic (DZ) twin pairs were interviewed with the Structured Clinical Interview for DSM-III-R Personality Disorders (SCID-II). Observed prevalence rates from a normal population study of more than 2,000 individuals were used in combination with data from the present study to generate statistics assumed to be valid for a normal twin population, and these statistics were used for structural equation modeling. The best-fitting models had a heritability of .60 for PDs generally, .37 for the eccentric (A) cluster, .60 for the emotional (B) cluster, and .62 for the fearful (C) cluster. Among the specific PDs, the heritability appeared to be .79 for narcissistic, .78 for obsessivecompulsive, .69 for borderline, .67 for histrionic, .61 for schizotypal, .57 for dependent, .54 for self-defeating,
Address reprint requests /0 Svellll Torgersen. Ph.D .. Center for Research in Clinical Psychology. Department of Psychology. Oslo University. Postbox 1039·Blindem. N-0315 Oslo. Nonmy.
