MR Dictionary

Exclusion restriction assumption

Synonyms: Exclusion restriction criterion, IV3 assumption, third MR assumption

Known as the third IV assumption, this states that the IV is not related to the outcome other than via the risk factor of interest. 

In general, MR this may be violated by horizontal pleiotropy. In MR exploring effects of maternal (or paternal) exposure on offspring, this may be violated by fetal (offspring genotype) (see MR for testing developmental origins). 

References

Other terms in 'Sources of bias and limitations in MR':