A longitudinal, population-based twin study of avoidant and obsessive-compulsive personality disorder traits from early to middle adulthood.
BACKGROUND
The phenotypic stability of avoidant personality disorder (AVPD) and obsessive-compulsive personality disorder (OCPD) has previously been found to be moderate. However, little is known about the longitudinal structure of genetic and environmental factors for these disorders separately and jointly, and to what extent genetic and environmental factors contribute to their stability.


METHODS
AVPD and OCPD criteria were assessed using the Structured Interview for DSM-IV Personality in 2793 young adult twins (1385 pairs, 23 singletons) from the Norwegian Institute of Public Health Twin Panel at wave 1 and 2282 (986 pairs, 310 singletons) of these on average 10 years later at wave 2. Longitudinal biometric models were fitted to AVPD and OCPD traits.


RESULTS
For twins who participated at both time-points, the number of endorsed sub-threshold criteria for both personality disorders (PDs) decreased 31% from wave 1 to wave 2. Phenotypic correlations between waves were 0.54 and 0.37 for AVPD and OCPD, respectively. The heritability estimates of the stable PD liabilities were 0.67 for AVPD and 0.53 for OCPD. The genetic correlations were 1.00 for AVPD and 0.72 for OCPD, while the unique environmental influences correlated 0.26 and 0.23, respectively. The correlation between the stable AVPD and OCPD liabilities was 0.39 of which 63% was attributable to genetic influences. Shared environmental factors did not significantly contribute to PD variance at either waves 1 or 2.


CONCLUSIONS
Phenotypic stability was moderate for AVPD and OCPD traits, and genetic factors contributed more than unique environmental factors to the stability both within and across phenotypes.
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
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Gjerde
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
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Czajkowski
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
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Røysamb
Department of Psychology,University of Oslo,Oslo,Norway.
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Ystrom
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
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Tambs
Virginia Institute for Psychiatric and Behavioral Genetics,Virginia Commonwealth University,Richmond,VA,USA.
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Aggen
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
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Ørstavik
Virginia Institute for Psychiatric and Behavioral Genetics,Virginia Commonwealth University,Richmond,VA,USA.
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Kendler
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
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Reichborn-Kjennerud
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
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Knudsen
D000328:Adult; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009664:Norway; D009771:Obsessive-Compulsive Disorder / Q000235:genetics*; D010554:Personality Disorders / Q000235:genetics*; D012042:Registries; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014427:Twins / Q000235:genetics*; D055815:Young Adult
Avoidant personality disorder traits; Norwegian Twin Registry; longitudinal studies; obsessive-compulsive personality traits; twin studies