LCV assumes that joint effect size distribution for two traits is a sum of two independent distributions: (1) a shared genetic component corresponding to L, whose values are proportional for both traits; and (2) a distribution that does not contribute to the genetic correlation (see Methods). We interpret the first distribution as ``mediated" effects (corresponding to π; Figure 1a) and the second distribution as ``direct" effects (corresponding to γ). The LCV model assumption is strictly weaker than the ``exclusion restriction" assumption of MR (see Methods).
