Medication adherence is a complex behavior that is influenced by numerous factors. Applying self-efficacy theory, the primary aim of this randomized controlled trial was to compare medication self-efficacy among patients with coronary heart disease who received: (a) text messages (TMs) for medication reminders and education, (b) TMs for education, or (c) no TMs. The second aim was to identify the personal (sociodemographic and clinical characteristics) and psychosocial factors that were associated with and predicted medication adherence.

Customized TMs were delivered over 30 days. Repeated measures analysis of variance was used to analyze medication self-efficacy. A multiple regression analysis was performed at baseline and follow-up to determine variables that were associated with and predicted self-reported medication adherence.

Among 90 subjects with mean age 59.2 years (standard deviation (SD) 9.4, range 35–83), total scores for medication self-efficacy improved over 30 days; however, there was no significant difference in this improvement as a function of the different treatment groups (p=0.64). Controlling for other variables in the model (age, education, depression, and social support), less depression (p=0.004) and higher social support (p=0.02) positively predicted higher medication adherence in the final model.

TM medication reminders and/or health education did not improve medication self-efficacy. Further theory testing of current and future models and interventions are required to understand variables related to self-efficacy and medication adherence. Addressing psychosocial factors such as depression and social support should be a priority to improve medication adherence among patients with coronary heart disease.