Mendelian Randomization, 2nd Edition

6

Interpretation of estimates from Mendelian randomization

In the previous chapters, we have introduced definitions of causal concepts and presented methods and examples of causal effects estimated using genetic variants as instrumental variables. In this chapter, we consider the interpretation of causal effects assessed and estimated in Mendelian randomization, and address the question of under what circumstances a Mendelian randomization estimate may be a reliable guide to the effect of an intervention on the exposure of interest in practice.

6.1 Internal and external validity

From the first discussions of Mendelian randomization, researchers have emphasized that the assumptions leading to the assertion of a causal relationship may ...