Confounding in statistical mediation analysis: What it is and how to address it

Matthew J. Valente, William E. Pelham, Heather Smyth, David Mackinnon

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


Psychology researchers are often interested in mechanisms underlying how randomized interventions affect outcomes such as substance use and mental health. Mediation analysis is a common statistical method for investigating psychological mechanisms that has benefited from exciting new methodological improvements over the last 2 decades. One of the most important new developments is methodology for estimating causal mediated effects using the potential outcomes framework for causal inference. Potential outcomes-based methods developed in epidemiology and statistics have important implications for understanding psychological mechanisms. We aim to provide a concise introduction to and illustration of these new methods and emphasize the importance of confounder adjustment. First, we review the traditional regression approach for estimating mediated effects. Second, we describe the potential outcomes framework. Third, we define what a confounder is and how the presence of a confounder can provide misleading evidence regarding mechanisms of interventions. Fourth, we describe experimental designs that can help rule out confounder bias. Fifth, we describe new statistical approaches to adjust for measured confounders of the mediator-outcome relation and sensitivity analyses to probe effects of unmeasured confounders on the mediated effect. All approaches are illustrated with application to a real counseling intervention dataset. Counseling psychologists interested in understanding the causal mechanisms of their interventions can benefit from incorporating the most up-to-date techniques into their mediation analyses.

Original languageEnglish (US)
Pages (from-to)659-671
Number of pages13
JournalJournal of counseling psychology
Issue number6
StatePublished - Nov 2017


  • Causal inference
  • Confounder adjustment
  • Mediation

ASJC Scopus subject areas

  • Social Psychology
  • Clinical Psychology
  • Psychiatry and Mental health


Dive into the research topics of 'Confounding in statistical mediation analysis: What it is and how to address it'. Together they form a unique fingerprint.

Cite this