The variance of the multivariable MR‐Egger estimate θ^1ME will be heavily influenced by the denominator in the bias term of Equation 12. As βX1 and βX2 become more highly correlated, the standard error of the causal estimate θ^1ME will increase, and in some circumstances, the estimate from multivariable MR‐Egger will be less precise than the estimate from univariable MR‐Egger. The precision of the causal estimates from multivariable MR‐Egger and univariable MR‐Egger is discussed further in the Web Appendix.
