The Mediating Role of Stress in the Relationship Between Self-Efficacy and Medication Adherence Among Patients with Heart Failure: A Cross-Sectional Study in the Aseer Region, Saudi Arabia

<b>Introduction</b>: Understanding how self-efficacy relates to medication adherence is crucial for patients with heart failure. This study investigated how stress mediates the relationship between self-efficacy and adherence to prescribed medication in patients with heart failure. <b>Methods</b>: This study employed a cross-sectional descriptive design. Using convenience sampling, 270 participants were recruited from the outpatient cardiology clinic in one of the largest hospitals in Aseer region, Saudi Arabia. Participants completed self-administered questionnaires, including the Perceived Stress Scale (PSS), Cardiac Self-Efficacy Scale (CSES), and Adherence to Refills and Medications Scale (ARMS). The data collection was conducted from January 2025 and ended in May 2025. <b>Results</b>: Results showed moderate stress (Mean = 20.17), high self-efficacy (Mean = 44.90), and a tendency toward medication non-adherence (Mean = 23.38). Stress was positively correlated with medication non-adherence (r = 0.392, <i>p</i> < 0.01), while self-efficacy was the strongest predictor of adherence (β = -0.345, <i>p</i> < 0.001). Mediation analysis confirmed that perceived stress partially mediates the relationship between self-efficacy and medication adherence (indirect effect β = -0.063, <i>p</i> = 0.003). <b>Conclusions</b>: Higher self-efficacy reduces perceived stress, which in turn leads to better medication adherence. From a nursing perspective, clinical practice should shift toward a "confidence-based" model of care. Routine psychological screening and targeted, demographic-specific interventions-particularly for younger patients and those with multiple comorbidities-are essential to empower patients and improve long-term health outcomes.