DNA used for genotyping ROS and MAP participants was collected from postmortem brain tissue, whole blood, or lymphocytes. The majority of samples were genotyped on the Affymetrix GeneChip 6.0 platform (Santa Clara, CA, USA) at the Broad Institute’s Center for Genotyping (n=1204) or the Translational Genomics Research Institute (n=674). Additionally, 566 participants were genotyped on the Illumina OmniQuad Express platform at Children’s Hospital of Philadelphia. The same QC protocol was applied to all datasets using PLINK15 (http://zzz.bwh.harvard.edu/plink/ ). We have limited analyses to participants of European decent. On the SNP level, we applied the following quality control (QC) filters: a genotype call rate>95%, MAF>0.01, misshap test 1×10−9, and a Hardy-Weinberg P<0.001. The EIGENSTRAT software was used to calculate principle components used to control for population sub-structure; the top three principal components (PC)s are sufficient to correct for residual stratification16.
