Some limitations of the present study should be highlighted, such as the fact that the data were not analyzed according to the gender of the probands or the FDRs, to specific OCS subtypes or dimensions, to the symptom severity or the treatment response rates. These analyses could not be performed due to insufficient detail in many of the studies. For example, it seems likely that the tic-related subtype of OCD is particularly familial and heritable but limited data exists [75]. In addition, it would have been important to have more studies describing the recurrence risks for OCD according to the age of onset of OCS. Furthermore, Twin studies were based on self-reported questionnaires rather than on direct interviewed individuals but their results were largely compatible with those of the controlled family and population-based studies.
