A general multilevel SEM framework for assessing multilevel mediation.

TLDR

Current multilevel mediation methods based on MLM are limited because they cannot handle Level‑2 outcomes, produce conflated indirect effect estimates, and exist in isolation, leaving no unified framework. This study aims to demonstrate that a multilevel structural equation modeling (MSEM) approach can address these limitations and to develop an integrative 2‑level MSEM framework that encompasses existing and new mediation models. The authors formulate a mathematical MSEM framework and provide software code and applied examples to illustrate its flexibility. The examples show that MSEM yields different substantive conclusions compared to MLM, highlighting its advantages.

Abstract

Several methods for testing mediation hypotheses with 2-level nested data have been proposed by researchers using a multilevel modeling (MLM) paradigm. However, these MLM approaches do not accommodate mediation pathways with Level-2 outcomes and may produce conflated estimates of between- and within-level components of indirect effects. Moreover, these methods have each appeared in isolation, so a unified framework that integrates the existing methods, as well as new multilevel mediation models, is lacking. Here we show that a multilevel structural equation modeling (MSEM) paradigm can overcome these 2 limitations of mediation analysis with MLM. We present an integrative 2-level MSEM mathematical framework that subsumes new and existing multilevel mediation approaches as special cases. We use several applied examples and accompanying software code to illustrate the flexibility of this framework and to show that different substantive conclusions can be drawn using MSEM versus MLM.