Investigating medication adherence in bipolar disorder based on the integrated behavioural model

Non-adherence to medication ranges between 20-60% in bipolar disorder (BPD), and can lead to serious health issues. To decrease these rates, intervention programs are required. However, identifying the predictors of medication adherence behavior (MAB) on a theoretical basis is essential for the effectiveness of interventions. Therefore this study aimed to develop and test the psychometric properties of an inventory targeting MAB and its predictors based on the Integrated Behavioral Model (IBM) for BPD patients, and investigate whether the relationships between the measures in the battery support the predictions of IBM. The sample consisted of 167 BPD patients; 14 inpatients, 153 outpatients receiving medical treatment. Data were collected through socio-demographic and medical information form, IBM Bipolar Disorder Medication Adherence Inventory (BDMAI), Medication Adherence Rating Scale, Medication Adherence Report Scale, Multidimensional Scale of Perceived Social Support, World Health Organization Quality of Life Instrument-Bref, and a blood-test measuring MAB. The findings showed high rates of MAB. However, according to self-report measures, 31% of the cases didn't use medications as prescribed. Furthermore, the strongest predictor of MAB was intention for MAB. Medication use habits, and self-efficacy contributed to MAB. Self-efficacy, attitudes, and perceived control also showed significant effects on intention for MAB. These provided evidence that BDMAI, which measures all components of IBM, is a valid and reliable tool, and can be utilized for differentiating disease severity among patients with similar non-adherence levels. It is expected that BDMAI is feasible for identifying individual components of MAB and developing MAB intervention programs targeting these components.