A longitudinal twin study of cluster A personality disorders.
BACKGROUND
While cluster A personality disorders (PDs) have been shown to be moderately heritable, we know little about the temporal stability of these genetic risk factors.


METHODS
Paranoid PD (PPD) and schizotypal PD (STPD) were assessed using the Structured Interview for DSM-IV Personality in 2793 young adult twins from the Norwegian Institute of Public Health Twin Panel at wave 1 and 2282 twins on average 10 years later at wave 2. Using the program Mx, we fitted a longitudinal latent factor model using the number of endorsed criteria for PPD and STPD.


RESULTS
The stability over time of the criteria counts for PPD and STPD, estimated as polychoric correlations, were +0.34 and +0.40, respectively. The best-fit longitudinal model included only additive genetic and individual-specific environmental factors with parameter estimates constrained to equality across the two waves. The cross-wave genetic and individual-specific environmental correlations for a latent cluster A factor were estimated to equal +1.00 and +0.13, respectively. The cross-time correlations for genetic and environmental effects specific to the individual PDs were estimated at +1.00 and +0.16-0.20, respectively. We found that 68% and 71% of the temporal stability of PPD and STPD derived, respectively, from the effect of genetic factors.


CONCLUSIONS
Shared genetic risk factors for two of the cluster A PDs are highly stable in adults over a 10-year period while environmental risk factors are relatively transient. Over two-thirds of the long-term stability of the common cluster A PD liability can be attributed to genetic influences.
Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University,Richmond,VA,USA.
K S
KS
Kendler
Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University,Richmond,VA,USA.
S H
SH
Aggen
Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University,Richmond,VA,USA.
M C
MC
Neale
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
G P
GP
Knudsen
Department of Psychology,University of Minnesota,Minneapolis,MN,USA.
R F
RF
Krueger
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
K
K
Tambs
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
N
N
Czajkowski
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
E
E
Ystrom
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
R E
RE
Ørstavik
Division of Mental Health,Norwegian Institute of Public Health,Oslo,Norway.
T
T
Reichborn-Kjennerud
D000293:Adolescent; D000328:Adult; D004200:Diseases in Twins / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009664:Norway / Q000453:epidemiology; D010260:Paranoid Personality Disorder / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D012042:Registries / Q000706:statistics & numerical data*; D012569:Schizotypal Personality Disorder / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D055815:Young Adult
schizotypal personality disorder