Bias in causal estimates from Mendelian randomization studies with weak instruments.

@article{Burgess2011BiasIC,
  title={Bias in causal estimates from Mendelian randomization studies with weak instruments.},
  author={Stephen Burgess and Simon G Thompson},
  journal={Statistics in medicine},
  year={2011},
  volume={30 11},
  pages={
          1312-23
        }
}
Mendelian randomization studies using genetic instrumental variables (IVs) are now being commonly used to estimate the causal association of a phenotype on an outcome. Even when the necessary underlying assumptions are valid, estimates from analyses using IVs are biased in finite samples. The source and nature of this bias appear poorly understood in the epidemiological field. We explain why the bias is in the direction of the confounded observational association, with magnitude relating to the… 
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