The strategy worked. There is compelling evidence that the larger the sample, the more genetic variants are identified (Sullivan & Geschwind, 2019). This has been observed across all psychiatric, substance use, and other complex health conditions and behaviors that have been studied. The Ns required to identify genetic variants vary as a function of the heritability of the trait, and associated complexities, such as the degree to which the environment plays a role. However, the evidence is unambiguous: Bigger is better. Extremely large, well-powered GWAS have led to replicable effects, for both individual genes and aggregate genetic liability scores created by summing associated genetic effects across the genome, in a way that earlier candidate gene, linkage, and smaller association studies did not (Duncan et al., 2019).
