Figure 1From: A further critique of the analytic strategy of adjusting for covariates to identify biologic mediationDecomposition of Total Effect of X on Y into Direct and Indirect Effects. The total average causal effect (ACE) of X on Y is achieved through two pathways, one which is termed "indirect'' because it operates through measured intermediate variable Z, and another that is termed "direct'' because it operates through no measured intermediates.Back to article page