We have reported elsewhere on the development of an 8-item Obsessive-Compulsive
Scale (OCS) contained in the Child Behavior Checklist (CBCL) to identify children
who meet criteria for DSM-IV obsessive-compulsive
disorder. Twin studies of obsessive-compulsive disorder have indicated a significant
genetic component to its expression.
To determine the relative contributions of genetic and environmental
influences on childhood obsessive-compulsive behavior using the CBCL OCS in
The CBCL data were received by survey of twins in the Netherlands Twin
Registry (NTR) and the Missouri Twin Study (USA/MOTWIN).
General community twin samples.
Participants were 4246 twin pairs aged 7 years, 2841 aged 10 years,
and 1562 aged 12 years (who also participated in the study at 7 and 10 years
of age) from the NTR and 1461 mixed-age twin pairs (average age, approximately
9 years) from the USA/MOTWIN.
Main Outcome Measures
Model fitting to test for genetic and environmental influences, sex
differences, and sibling interaction/rater contrast effects on the CBCL OCS.
In each case, the best-fitting model was one that indicated significant
additive genetic influences (range, 45%-58%; 95% confidence interval [CI],
45%-61%), and unique environmental influences (range, 42%-55%; 95% CI, 39%-55%),
with shared environmental influences in the NTR sample aged 12 years (16%).
Sex differences were seen in the mixed-age USA/MOTWIN model, but not in the
NTR samples. No evidence of dominance, sibling interaction, or rater-contrast
effects was seen. These data were relatively consistent across age and cultures.
The CBCL OCS is influenced by genetic factors (approximately 55%) and
unique environmental factors (approximately 45%) in the younger sample, with
common environmental influences only at 12 years of age. These effects do
not vary with differences in sex or sibling interaction/rater contrast effects.
Our data reveal higher genetic influences for obsessive-compulsive behavior
and do not demonstrate genetic differences across sex.