What did Nestadt et all find.
-Reviewed previous twin and family studies.
-Found that people with a first-degree relative (parent, sibling, child) with OCD had a 5× greater risk of having OCD themselves compared to the general population.
-Also found concordance rates in twin studies:
-MZ twins (identical) had a higher concordance rate for OCD than DZ twins (non-identical), suggesting a genetic component.