Obsessive-compulsive disorder, tics and anxiety in 6-year-old twins

Institute of Psychiatry, Kings College London, UK.
Psychological Medicine (Impact Factor: 5.94). 02/2007; 37(1):39-48. DOI: 10.1017/S0033291706008816
Source: PubMed


Previous reports of genetic influences on obsessive-compulsive disorder (OCD) symptoms have suggested moderate heritability. Family history studies of co-morbidity have found familial aggregation with tics, especially for early-onset OCD, and familial aggregation with anxiety disorders.
Heritability of OCD and familial aggregation of OCD, tics and anxiety disorders were investigated in a community sample of 6-year-old twins using a two-phase design in which 4662 twin pairs were sampled and 854 pairs were assessed in the second phase by maternal-informant diagnostic interview using DSM-IV criteria.
In the multivariate model combined additive genetic and common environmental effects were estimated as 47% for sub-threshold OCD, and the model was unable to distinguish these sources of familial aggregation. There were strong familial aggregations between sub-threshold OCD and tics and between sub-threshold OCD and other anxiety disorders (80% and 97% respectively), although again specific sources could not be distinguished.
The findings are consistent with the hypothesis of a tic-related early-onset OCD phenotype, but also with the hypothesis of an anxiety-related early-onset OCD phenotype.

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    • "Results from the majority of these studies demonstrate that at least some forms of OCD are familial, and the findings from twin studies summarized above provide evidence that this familiality is due in part to genetic factors. However, it is also evident that environmental/cultural factors influence OC behaviors and are also transmitted within families.29 These nongenetic factors unquestionably influence the manifestation of OC behaviors as evidenced from twin studies that consistently demonstrate that the concordance rate of MZ twins for OC behaviors and OCD is always less than 1.0. "
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    ABSTRACT: Obsessive-compulsive disorder (OCD) is a serious psychiatric disorder that affects approximately 2% of the populations of children and adults. Family aggregation studies have demonstrated that OCD is familial, and results from twin studies demonstrate that the familiality is due in part to genetic factors. Only three genome-wide linkage studies have been completed to date, with suggestive but not definitive results. In addition, over 80 candidate gene studies have been published. Most of these studies have focused on genes in the serotonergic and dopaminergic pathways. Unfortunately, none have achieved genome-wide significance, and, with the exception of the glutamate transporter gene, none have been replicated. Future research will require the collaboration of multidisciplinary teams of investigators to (i) achieve sufficiently large samples of individuals with OCD; (ii) apply the state-of-the-art laboratory techniques; and (iii) perform the bioinformatic analyses essential to the identification of risk loci.
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    • "Van Grootheest et al. (2007) found that stability of OC behaviour in children, using the CBCL-OCS at ages 7, 10 and 12 years in a longitudinal design, was influenced by genes and both shared and non-shared environmental factors. Bolton et al. (2007) examined 6-year-old twins on OC symptoms ; the effect of familial aggregation was estimated as 47 % for subthreshold OCD, but the study missed power to distinguish shared environment from genetic factors. In summary, twin studies are suggestive of genes being important for variation in OC behaviour in children. "
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    ABSTRACT: The contribution of genetic factors to obsessive-compulsive (OC) symptoms has not been examined using a large population-based sample of adults. Furthermore, the extent to which there are qualitative and quantitative differences in genetic architecture between men and women with OC symptoms has not been elucidated. We obtained the Young Adult Self Report Obsessive-Compulsive Scale (YASR-OCS) from a group of 5893 monozygotic (MZ) and dizygotic (DZ) twins, and 1304 additional siblings from the population-based Netherlands Twin Register. Structural equation modelling was used to decompose the variation in OC behaviour into genetic and environmental components and analyse quantitative and qualitative sex differences. Familial resemblance was the same for DZ twins and non-twin siblings, which means that there was no evidence for a special twin environment. The same genetic risk factors for OC behaviour were expressed in men and women. Depending on the choice of fit index, we found small (39% for men and 50% for women) or no sex differences (47% for both men and women) in heritability. The remaining variance in liability was due to individual-specific environment. OC behaviour showed a moderate heritability. At most, small quantitative sex differences were found in the genetic architecture of OC behaviour, and no qualitative sex differences.
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