# Pleiotropy and MR Assumptions

**URL:** <https://isgw-forum.colorado.edu/t/pleiotropy-and-mr-assumptions/898>\
**Category:** Day 7\
**Created:** [June 11, 2026, 3:47pm UTC](https://isgw-forum.colorado.edu/t/pleiotropy-and-mr-assumptions/898 "2026-06-11T15:47:57Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![anonymous](https://isgw-forum.colorado.edu/letter_avatar_proxy/v4/letter/a/8491ac/32.png) [@anonymous](https://isgw-forum.colorado.edu/u/anonymous)\
**Post date:** [June 11, 2026, 3:47pm UTC](https://isgw-forum.colorado.edu/t/pleiotropy-and-mr-assumptions/898/1 "2026-06-11T15:47:57Z")

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Does the pliatropy (I can’t spell) concern influence the second assumption as well (i.e. no SNP influences on confounders)? Thanks 🙂

> Replying to “Does the pliatropy (I can’t spell) concern influen…”:

it certainly does. A way to check is to do a phenome-wide association study on your SNP instrument to see what it is associated with, and exclude it if it’s associated with a potential confounder

> Replying to “Does the pliatropy (I can’t spell) concern influen…”:

If the effect is of the SNP → confounder (pleiotropy), it would violate the third assumption and if the associaiton is confounder (e.g. pop strat) → SNP, the second assumption is violated!