Residualization and PCA were performed on CT data of the adult participants from ENIGMA-CTRL, UKB and IMAGEN-T2 datasets separately. The relations among the resulting standard loadings of PCs were examined using Pearson’s correlation. As reported below, the first component (PC1) was highly correlated across datasets and, consequently, a single PC1 (Combined-PC1) was calculated with the aggregated data of adult participants from these datasets for the subsequent analyses.
