Research Paper Volume 12, Issue 3 pp 2584—2594

Figure 1. Principles of using genetic variants as instrumental variable to estimate the causal influence of exposure factors on disease. There is a strong correlation between genetic variation and exposure factors (γ≠0), and the genetic variation is independent of the confounding factors affecting the relationship between “exposure factors -outcomes” (φ1=0). Furthermore, genetic variation can only affect the outcomes through exposure factors but not other paths (φ2 = 0).