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Dimensional representations of DSM-IV Cluster A personality disorders in a population-based sample of Norwegian twins: a multivariate study

Published online by Cambridge University Press:  08 August 2006

KENNETH S. KENDLER ,
NIKOLAI CZAJKOWSKI ,
KRISTIAN TAMBS ,
SVENN TORGERSEN ,
STEVEN H. AGGEN ,
MICHAEL C. NEALE  and
TED REICHBORN-KJENNERUD
KENNETH S. KENDLER
Affiliation:
Department of Psychiatry, Medical College of Virginia of Virginia Commonwealth University, Richmond, VA, USA Department of Human Genetics, Medical College of Virginia of Virginia Commonwealth University, Richmond, VA, USA
NIKOLAI CZAJKOWSKI
Affiliation:
Division of Mental Health, Norwegian Institute of Public Health, Norway
KRISTIAN TAMBS
Affiliation:
Division of Mental Health, Norwegian Institute of Public Health, Norway
SVENN TORGERSEN
Affiliation:
Institute of Psychology, University of Oslo, Norway Center for Child and Adolescent Mental Health, Eastern and Southern Norway Nic Waal's Institute, Norway
STEVEN H. AGGEN
Affiliation:
Department of Psychiatry, Medical College of Virginia of Virginia Commonwealth University, Richmond, VA, USA
MICHAEL C. NEALE
Affiliation:
Department of Psychiatry, Medical College of Virginia of Virginia Commonwealth University, Richmond, VA, USA Department of Human Genetics, Medical College of Virginia of Virginia Commonwealth University, Richmond, VA, USA
TED REICHBORN-KJENNERUD
Affiliation:
Division of Mental Health, Norwegian Institute of Public Health, Norway Institute of Psychiatry, University of Oslo, Norway
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Abstract

Background. The ‘odd’ or ‘Cluster A’ personality disorders (PDs) – paranoid, schizoid and schizotypal PDs – were created in DSM-III with little empirical foundation. We have examined the relationship between the genetic and environmental risk factors for dimensional representations of these three personality disorders.

Method. These personality disorders were assessed using the Structured Interview for DSM-IV Personality (SIDP-IV) in 1386 young adult twin pairs from the Norwegian Institute of Public Health Twin Panel. Using Mx, a single-factor independent pathway twin model was fitted to the number of endorsed criteria for the three disorders.

Results. The best-fit model included genetic and unique environmental common factors and genetic and unique environmental effects specific to each personality disorder. Total heritability was modest for these personality disorders and ranged from 21% to 28%. Loadings on the common genetic and unique environmental factors were substantially higher for schizotypal than for paranoid or schizoid PD. The proportion of genetic liability shared with all Cluster A disorders was estimated at 100, 43 and 26% respectively for schizotypal, paranoid and schizoid PDs.

Conclusion. In support of the validity of the Cluster A construct, dimensional representations of schizotypal, paranoid and schizoid PD are all modestly heritable and share a portion of their genetic and environmental risk factors. No evidence was found for shared environmental or sex effects for these PDs. Schizotypal PD most closely reflects the genetic and environmental liability common to all three Cluster A disorders. These results should be interpreted in the context of the limited power of this sample.

Type
Original Article
Information
Psychological Medicine , Volume 36 , Issue 11 , November 2006 , pp. 1583 - 1591
Copyright
© 2006 Cambridge University Press

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