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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    • "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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