Background: The present research aimed to investigate the efficacy of a multifaceted intervention that included motivational interviewing (MI) and psychoeducation in improving medication adherence (MA) among patients with bipolar disorder (BD).

Method: A multicenter, cluster randomized, observer-blind, controlled, parallel-group trial was conducted in ten academic centers in Iran. Patients with BD were randomly assigned to the experimental group (EXP; n = 136) or the usual care group (UC; n = 134). The EXP group received five sessions of MI and psychoeducation together with their family members. The primary outcome measure was changes in scores on the Medication Adherence Rating Scale from baseline to 6 months post-intervention. Other outcome measures included serum levels of mood stabilizers, clinical symptoms, quality of life, as well as measures of intention, beliefs about medicine, perceived behavioral control, automaticity, action and coping planning, and adverse reactions.

Results: Medication adherence improved over time in both groups, but patients in the EXP group improved more (baseline score: 6.03; score at the sixth month: 9.55) than patients in the UC group (baseline score: 6.17; score at the sixth month: 6.67). In addition, patients in the EXP group showed greater improvement than patients in the UC group in almost all secondary outcomes 6 months following the intervention.

Conclusions: Multifaceted interventions that include motivational-interviewing and psychoeducation can significantly improve MA and clinical and functional outcomes in patients with BD.