A robust example of collider bias in a genetic association study

A recent paper by Aschard et al described the potential for \"collider bias\" when adjusting for heritable covariates in genetic association studies1. However, in their examples the authors acknowledged that they could not exclude the possibility of a true biological explanation for the genetic association seen only in the adjusted model. Furthermore, the extent to which this bias could create a completely spurious genetic association, rather than just modify the magnitude of the effect,2 remains unclear.\n\nCollider bias describes the artificial association created between two uncorrelated exposures (A and B) when a shared outcome (X) is included in the model as a covariate (Figure 1). We sought to definitively illustrate collider bias by deliberately inducing it to generate a biologically implausible SNP-phenotype association. Both sex (A) and autosomal genetic determinants ...