based on genotype or the associations present in this study. In addition to the subcortical structures of the brain, we examined the genetic effects of a measure of global head size, the ICV. The ICV was calculated as: 1/(determinant of a rotation-translation matrix obtained after affine registration to a common study template and multiplied by the template volume (1,948,105 mm3)). After image processing, each image was inspected individually to identify poorly segmented structures. Each site contributed histograms of the distribution of volumes for the left and right hemisphere structures (and a measure of asymmetry) of each subcortical region used in the analysis. Scans marked as outliers (> 3 standard deviations from the mean) based on the histogram plots were re-checked at each site to locate any errors. If a scan had an outlier for a given structure, but was segmented properly, it was retained in the analysis. Site-specific phenotype histograms, Manhattan plots and quantile–quantile plots from each participating site are available on the ENIGMA website (http://enigma.ini.usc.edu/publications/enigma-2/).
