Here we report the results of a GWAS including a sample of 1 406 patients with OCD, that was predominantly family-based, but which also included a case-control subsample to increase power (resulting in a total sample of 5 061 individuals). The study identified interesting candidate genes for OCD, but failed to detect any genome-wide significant findings. This is similar to what has been observed for other psychiatric phenotypes such as schizophrenia, for which genome-wide significant findings were only achieved after either starting with more samples in the discovery step 35, 36 or making use of large follow-up samples, that were orders of magnitude larger then the original discovery samples 37, 38. We suspect that, with additional samples, the findings of genetic studies for OCD will be more robust, and our currently suggestive findings may reach genome-wide significance.
