The standard procedure in ENIGMA has been collation of individual‐participant data (IPD; e.g., value of CTh, SA, subcortical volume, and intracranial volume) from multiple studies, without requiring the sharing or centralization of the raw MRI data, as was done in OBIC. The advantage of meta‐analysis on IPD without the need to exchange raw data is of particular relevance in the context of the new European law, that is, the General Data Protection Regulation 2016/679, regulating data protection and privacy for all individual citizens of the European Union (https://gdpr-info.eu/). Using standardized protocols for data processing and quality control (see also: http://enigma.ini.usc.edu/protocols/), all data are processed at each site locally. Standardization of protocols, within working groups and across working groups, ensures low methodological heterogeneity across sites and working groups. IPD can subsequently be used in two different statistical approaches: A two‐stage or a one‐stage approach (Boedhoe et al., 2019). In the two‐stage approach, IPD are first analyzed for each sample separately to obtain summary results (e.g., effect size estimates, confidence intervals, and so on), which are then used for standard meta‐analysis. In
