Candidate gene association studies usually have moderate sample sizes and are much cheaper than GWAS, where the genes examined are selected according to the linkage/GWAS study results or biological hypotheses. However, because of population heterogeneity and liberal statistical thresholds (compared with GWAS) that often are applied, hypothesis-driven candidate gene association studies generally are considered to have an uncertain yield.38 On the other hand, the abundant results obtained using this approach provide greater depth of exploration of potential targets and offer valuable replication for other unbiased approaches; e.g., genome-wide linkage study and GWAS.
