The necessity-concern framework in the assessment of treatment adherence of psychiatric patients and the role of polypharmacy in a Spanish sample

Objective: This study compares three measures (necessity and concern scores, the necessity-concern differential, and a skeptical attitude vs. three other attitudes) for studying the relationship between the necessity-concern framework and treatment adherence after considering the number of prescribed drugs. Methods: The sample included 588 consecutive adult psychiatric outpatients in the Canary Islands, Spain. The necessity-concern framework was assessed using a specific subscale of the Beliefs about Medicines Questionnaire. Adherence (yes/no) to 1,101 prescribed psychiatric drugs was assessed using the Sidorkiewicz adherence tool. Results: In the three logistic regression models including 1,101 drugs, with adherence as the dependent variable, the highly significant odds ratios (ORs) and their 95% confidence intervals (CIs) were (a) OR = 1.57 (CI = 1.37–1.79) for necessity and OR = 0.747 (CI = 0.660–0.847) for concern; (b) OR = 1.44 (CI = 1.32–1.58) for the necessity-concern differential; and (c) OR = 0.452 (CI = 0.343–0.597) for a skeptical attitude (yes/no), defined as low necessity and high concern. In patients taking five or six drugs, adherence was associated with extremely high/low ORs for necessity, concern, and the differential. Conclusion: If replicated, our results suggest clinicians need to pay careful attention to each drug in each patient taking five or six drugs, emphasize necessity, and listen carefully to patient concerns.