Association studies in psychiatry have traditionally had small sample sizes (< 1000 total subjects). For even a modest amount of genotyping in a candidate gene (10 SNPs), 90% power to detect a genotypic relative risk of 1.16 at MAF 0.30 requires 3600 cases and 3600 controls. It is possible to speculate that larger genetic effects exist at smaller MAF (0.005–0.05). Investigators, reviewers and editors need to be cognizant of these requirements, as smaller samples may be difficult to interpret due to inadequate power.
