Table 1.

Threats to validity in study designs.

	Case-control study	Cohort study	Genome-wide association study
Bias	Selection bias Recall bias Inappropriate matching Reverse causation	Selection bias Misclassification Length-time bias Reverse causation Loss to follow-up	Phenotype misclassification Inappropriate controls Genomic inflation
Confounding	Unmeasured confounders	Unmeasured confounders	Population stratification
Chance	Multiple testing Power	Multiple testing Power	Multiple testing False discovery rate Rare variants Power
Generalizability	Study-specific	Cohort-specific	Race/region-specific Phenotype-specific