Of those individuals with array genotypes, 1431 were selected for 11× whole genome sequencing. Among the 1431 sequenced participants, 406 were members of a monozygotic twin pair and, for each monozygotic twin pair, we sequenced only one member of the pair and copied the sequence to the other twin resulting in a total of 1837 individuals for whom whole-genome sequence variant calls were available. Monozygotic twin genomes were copied under the assumption that their genomes are identical or, at the very least, so similar that any genetic differences between the two twins would be indistinguishable from error at 11× depth sequencing. Table 1 contains descriptive information on the sample. Online Supplementary Table S1 shows the 17 × 17 endophenotype correlation matrix. All of the endophenotypes shows moderate to strong twin-based heritability except the two startle difference scores.
