Our results indicate the potential for selection/attrition to generate biased and potentially misleading estimates of both phenotypic and genotypic associations. In particular, when polygenic scores (associated with a phenotype) that combine many genetic variants are used, association between the phenotype and participation will cause the score to be more strongly related to participation than each individual variant is. This, in turn, can potentially lead to serious bias. For this reason, studies using polygenic scores, genome-wide allelic scores20 and/or whole-genome genetic correlations21,22 are most at risk of producing biased and potentially misleading results where there is reason to believe the actual study sample is not representative of the intended study population, but the mechanism of selection is unknown.
