DNA was extracted from dried blood spot samples and whole genome amplified in triplicates as described previously56,57. Genotyping was performed at the Broad Institute of Harvard and MIT (Cambridge, MA, USA) using Illumina’s Beadarrays (PsychChip; Illumina, CA, San Diego, USA) according to the manufacturer’s protocols. Genotypes were a result of merging call sets from three different calling algorithms (GenCall, Birdseed and Zcall). GenCall58 and Birdseed59 were used to call genotypes with minor allele frequency (maf) > 0.01 and zCall60 was used to call genotypes with maf <0.01. The merging was done after pre-QC on individual call sets.
