According to the 18 OCD family studies included in the analyses, OCD was 7.2 times more frequent in OCD families, when compared to control families. These estimates are almost twice higher than those from the last meta-analysis published in 2001 [19]. One conceivable explanation for these different ratings could be the fact that the current study included studies with larger samples, interviewed with validated assessment tools and based on reliable diagnostic criteria. Furthermore, considering the secrecy characteristic of OCD, the higher rates may be due to the fact that the current analyses included subjects that were directly interviewed.
