Correlates of Medication Adherence Among Patients With Bipolar Disorder

Abstract

To identify and describe correlates of medication adherence in a large, national sample of outpatients with bipolar disorder. Data were collected via a self-report, Web-based survey in January and February of 2008 from US patients aged 18-65 years who reported a diagnosis of bipolar disorder and current use of psychotropic medication. Patients with a Composite International Diagnostic Interview-bipolar disorder (CIDI-bipolar disorder) score ≥ 7, indicating a high risk of bipolar disorder, were included in the analyses. Medication adherence was assessed via the Morisky Medication Adherence Scale, with scores ≥ 2 being considered nonadherent. The primary analysis was a multivariate binomial logistic regression with adherence as the dependent variable. Covariates included patient demographics, physical health measures including Medical Outcomes Study 8-item Short-Form Health Survey physical summary score, number of manic and depressive episodes, 24-item Behavior and Symptom Identification Scale (BASIS-24), Liverpool University Neuroleptic Side-Effect Rating Scale (LUNSERS), Satisfaction With Antipsychotic Medication scale (SWAM), and current psychiatric medication use. Nearly half (49.5%) of the 1,052 bipolar patients in the analysis were classified as being nonadherent. Adherence was positively associated with college degree, higher SWAM total score, and monotherapy treatment. Adherence was negatively associated with female sex, alcohol use, BASIS-24 total score, and LUNSERS total score. Nonadherence is common among patients with bipolar disorder. By addressing tolerability issues and treatment satisfaction, which are both significant correlates of adherence, health care providers may be able to improve adherence and, ultimately, treatment outcomes.