ENIGMA‐OCD has brought together OCD experts from all over the world to re‐analyze historical MRI data using meta‐ and mega‐analyses. This has not only resulted in important contributions to the literature on brain alterations in OCD, but has also stimulated international collaboration and sharing of OCD imaging data from sites across the globe. While as outlined earlier, there are many questions still to address in the growing ENIGMA‐OCD dataset, the findings and the successful model of international collaboration have already spurred new studies. For example, to address the lack of harmonization of data acquisition and the lack of detail on clinical profile, and to address the confound of medication in the ENIGMA‐OCD dataset, five of the participating ENIGMA‐OCD sites, representing five continents, are now funded by NIMH (PI: H. Blair Simpson) to conduct the largest neurocognitive and multimodal‐imaging study in medication‐free subjects with OCD to date. Specifically, we will recruit 250 medication‐free adults with OCD, 100 unaffected adult siblings of individuals with OCD, and 250 healthy control subjects. All will receive clinical evaluation, neurocognitive assessment, and MRI, focusing on morphometry
