Strategies to Measure Direct and Indirect Effects in Multi-mediator Models

Abstract

The analysis of mediators, multi-mediators, confounders, and suppression variables often presents problems to the scientists that need to interpret them correctly. After clarifying main differences among these terms, this paper focuses on the techniques to conduct and estimate multi-mediation effects. Multi-mediator effects are very common in social science literature, however, many studies do not report their analysis, or even worse, do not explore the significance of the indirect effects in the outcome variable. In exploring the underlying mechanism of observed variables, mediation addresses a key important aspect: Mediation explains how the changes occur. The measurement of direct and indirect effects involves the combination of several techniques, especially under multiple mediators. The objective of this paper is to show different approaches that should be used to investigate indirect and direct effects in order to shed some light on how to conduct a mediation analysis, how to assess the model estimation, and how to interpret mediation effects. The main conclusion of this paper is that by applying traditional methodologies (causal steps, product of coefficients, and the indirect approach), the real mediation effect could be overestimated or underestimated. This paper explains new methods that overcome the difficulties of traditional approaches. Examples of Mplus syntax are provided to facilitate the use of these methods in this application. Keywords: mediator, moderator, cofounder, multi-mediators The Concept of Mediation and Approaches to Test Multi-mediation Effects In social sciences, researchers are interested in explaining the mechanisms that illustrate the relationship between an independent variable (X) and a dependent variable (Y) (Figure 1). This paper extents previous studies by considering the difficulties of analyzing multi-mediation effects that appear in complex situations in which there is a chain of effects that mediate the relationship between X and Y. The main contribution of this paper is to provide a methodology that includes how to conduct and assess the mediation analysis and interpret results.Essentially, mediation analysis is the set of techniques used in conducting and testing the mediation