Theory as mediating variables: Why aren't community interventions working as desired?

PURPOSE: This paper discusses the role of theory in explaining why recent community intervention trials for chronic disease prevention are not achieving the level of desired behavioral effects and related outcomes. METHOD: Literature review and analysis are used to derive an explanation. RESULTS: All interventions (e.g., school nutrition education) effect change in behavioral outcomes (e.g., dietary behaviors) through mediating variables. Selected from the social and behavioral theories, these mediating variables can be environmental (e.g., increased availability of the targeted food) or intrapersonal (e.g., increased self-efficacy for eating the targeted foods). The percentage of variance of the outcome variables accounted for by the mediating variables has been modest to low. This places one limit on how much change interventions can achieve in outcomes. Another limit is imposed by the ability of the interventions to produce change in the mediating variables, which also has been weak. CONCLUSIONS: More basic research should examine: (i) the relationships between mediating variables and behavior; and (ii) how interventions effect change in mediating variables. One possible six phase process for developing such research is described.