Mediators and moderators: Theoretical and methodological implications in stress and health psychology research

The concepts of mediators and moderators are often confused in psychologica l research. Most empirical studies use these two terms interchangeably and analyse their effects using the same statistical approaches. Nevertheless, it is very important to distinguish between their properties as it permits the conceptualization of complex theoretical models and different levels of analysis. In the domain of stress research, the dis tinction between these two types of variable is also essential because it underscores the histori cal evolution of different models. The earliest behavioural models of stres s (stimulus-response) were simple interactional models, where by negative c onsequences of stress could be explained jointly by environmental and perso nal variables, and above all by their incompatibility. in this context, mod erators play an important role. Numerous personal variables (personality tr aits) and environmental variables (social support) serve as of buffers betw een stressors (work, life events) and outcomes (well-being, illness). Altho ugh these interactional models are important for emphasizing individual vul nerability to stress, they do nor explain the underlying psychological proc esses at work. For this reason, the evolution of models requires the identi fication of psychological and/or biological mediators that explain how pred ictive variables (environment and personality) have an impact on individual health. The transactional model of stress is an example of such neo-behavi oural models. The identification of distinct models and variables with spec ific properties also requires the selection of appropriate statistical anal yses. Testing the effects of moderators doer nor use the same Kind of analy sis as for testing the effects of mediators. ANOVA and hierarchical regress ion analyses are the most appropriate methods for testing moderator effects , while path analyses with Lisrel allow for the examination of mediator eff ects of a given variable relative to two other variables. Finally, the clar ification of these different issues has value beyond the domain of stress t heory.