One dbGaP cohort with drug abuse data available on both AA and EA participants was utilized for independent replication of genome-wide significant SNP associations: the Genetic Association Information Network (GAIN) “GWAS of Schizophrenia” (dbGaP accession number phs000021.v3.p2). We focused only on the schizophrenia controls consented for general research (979 AAs and 1,442 EAs) and processed them using the same quality control procedures as used for the discovery cohorts.
