Psychological Medicine

Original Article

Genetic and environmental influences on dimensional representations of DSM-IV cluster C personality disorders: a population-based multivariate twin study

a1 Division of Mental Health, Norwegian Institute of Public Health, Oslo, Norway
a2 Institute of Psychiatry, University of Oslo, Oslo, Norway
a3 Institute of Psychology, University of Oslo, Oslo, Norway
a4 The Virginia Institute for Psychiatric and Behavioral Genetics and Departments of Psychiatry and Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond, VA, USA

Article author query
reichborn-kjennerud t   [PubMed][Google Scholar] 
czajkowski n   [PubMed][Google Scholar] 
neale mc   [PubMed][Google Scholar] 
orstavik re   [PubMed][Google Scholar] 
torgersen s   [PubMed][Google Scholar] 
tambs k   [PubMed][Google Scholar] 
roysamb e   [PubMed][Google Scholar] 
harris jr   [PubMed][Google Scholar] 
kendler ks   [PubMed][Google Scholar] 


Background. The DSM-IV cluster C Axis II disorders include avoidant (AVPD), dependent (DEPD) and obsessive-compulsive (OCPD) personality disorders. We aimed to estimate the genetic and environmental influences on dimensional representations of these disorders and examine the validity of the cluster C construct by determining to what extent common familial factors influence the individual PDs.

Method. PDs were assessed using the Structured Interview for DSM-IV Personality (SIDP-IV) in a sample of 1386 young adult twin pairs from the Norwegian Institute of Public Health Twin Panel (NIPHTP). A single-factor independent pathway multivariate model was applied to the number of endorsed criteria for the three cluster C disorders, using the statistical modeling program Mx.

Results. The best-fitting model included genetic and unique environmental factors only, and equated parameters for males and females. Heritability ranged from 27% to 35%. The proportion of genetic variance explained by a common factor was 83, 48 and 15% respectively for AVPD, DEPD and OCPD. Common genetic and environmental factors accounted for 54% and 64% respectively of the variance in AVPD and DEPD but only 11% of the variance in OCPD.

Conclusion. Cluster C PDs are moderately heritable. No evidence was found for shared environmental or sex effects. Common genetic and individual environmental factors account for a substantial proportion of the variance in AVPD and DEPD. However, OCPD appears to be largely etiologically distinct from the other two PDs. The results do not support the validity of the DSM-IV cluster C construct in its present form.

(Published Online November 30 2006)

c1 Norwegian Institute of Public Health, Box 4404, Nydalen, N-0403 Oslo, Norway. (Email: