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. Author manuscript; available in PMC: 2022 Dec 1.
Published in final edited form as: Curr Protoc. 2021 Dec;1(12):e335. doi: 10.1002/cpz1.335

Figure 5.

Figure 5

Illustration of vertical (A) and horizontal (B) pleiotropy as diagrammed by directed acyclic graphs. Depiction shown for genetic variant G, exposures X1 and X2, outcome Y, confounder of the X1-outcome association U1, and confounder of the X2-outcome association U2. In the vertical pleiotropy case illustrated in A, genetic variant G is associated with exposure X1, which exerts a downstream causal effect on exposure X2, which then exerts a causal effect on outcome Y. In the horizontal pleiotropy case illustrated in B, genetic variant G is associated with exposure X1 and independently associated with unrelated exposure X2, both exposures of which are associated with outcome Y.