Abstract
This systematic review applied meta-analytic procedures to integrate primary research that examined blood pressure outcomes of medication adherence interventions. Random-effects model analysis calculated standardized mean difference effect sizes. Exploratory dichotomous and continuous moderator analyses using meta-analytic analogues of ANOVA and regression were performed. Codable data were extracted from 156 reports with 60,876 participants. The overall weighted mean difference systolic effect size was 0.235 across 161 treatment versus control comparisons. The diastolic effect size was 0.189 from 181 comparisons. Effect sizes were significantly heterogeneous. Common risks of bias included lack of allocation concealment, unmasked data collectors, and absent intention-to-treat analyses. Exploratory moderator analyses suggested that habit-based interventions may be most effective. The largest effect sizes were for interventions delivered by pharmacists. The modest magnitude effect sizes suggest future research should explore novel higher dose interventions that might address multiple levels of influence on adherence behavior.