The results presented herein should be considered in light of several limitations. First, the phenotypes examined are based on self-report data, which do not offer the possibility of external verification and are subject to reporting bias. We attempted to mitigate potential issues by imposing cut-offs that allowed for variation in responses while restricting values to a reasonable realm of possibility. Second, several of the ancestry groups (American, East Asian, and South Asian descent) included in these analyses were rather small, resulting in large standard errors around parameter estimates for both individual variant analyses and aggregate tests (e.g., GCTA). While the European and African descent groups were larger and more statistically powerful, substantial sample sizes are necessary to reliably detect low heritability using GCTA, and these results should be interpreted with caution.
