Medication adherence among adults with mental illnesses in Oman: A cross-sectional study

Medication adherence is essential for achieving therapeutic outcomes in individuals with mental illnesses, yet remains a challenge, particularly in low- and middle-income countries. This study assessed adherence to psychotropic medications among Omani adults using complementary self-reported and pharmacy-based tools and examined associated sociodemographic and clinical factors.

A cross-sectional study was conducted among 246 adults attending psychiatric outpatient departments at two tertiary referral hospitals in Oman. Participants were Omani nationals aged ≥18 years, diagnosed with a mental illness for at least six months, and prescribed psychotropic medication. Adherence was measured using the 10-item Medication Adherence Rating Scale (MARS) and the Proportion of Days Covered (PDC) based on a 3-month refill history. A structured questionnaire captured demographic and clinical data. Statistical analyses included descriptive statistics, t-tests, ANOVA, Pearson correlation, Chi-square tests, and Cohen's kappa to explore associations and agreement between measures.

Based on PDC, 85.3% of participants were adherent, compared with 51.4% via MARS, demonstrating a clear discrepancy between objective and subjective measures. Lower MARS scores were associated with younger age, higher education, and more frequent hospitalizations (r = -.168, P = .008). Agreement between MARS and PDC was poor (κ = 0.03, P = 0.59).

Although refill-based adherence appeared high, self-reports indicated considerable non-adherence, suggesting objective data may overestimate adherence. Sociodemographic factors, particularly age, marital status, and education, influenced adherence patterns. Employing multiple assessment methods and tailoring interventions to patient profiles are essential to improve psychiatric treatment outcomes.