Effect of necessity-concern framework and polypharmacy on treatment adherence in psychiatric patients. Comparing an Argentinian with a Spanish sample

Objective: We aimed to replicate a prior Spanish study of medication adherence where logistic regression models provided highly significant odds ratios (ORs) for three continuous scores: necessity, concern and the necessity-concern differential, and a dichotomous variable: skeptical attitude. Adherence ORs in the necessity-concern framework were very strong in patients taking five or six medications. Methods: The sample comprised consecutive adult psychiatric outpatients in Mendoza, Argentina. The necessity-concerns framework was assessed using a subscale of the Beliefs about Medicines Questionnaire. Adherence (yes/no) to prescribed psychiatric medications was assessed by the Sidorkiewicz adherence tool. Results: When compared with the Spanish sample, the Argentinian group (508 patients with 875 medications) was characterized by: (1) significantly stronger adherence ORs with the necessity-concern framework, (2) significantly lower number of medications per patient and percentage of patients with marked psychiatric polypharmacy (≥4 medications), (3) though a higher number of medications still was significantly associated with poor adherence. Conclusions: The Argentinian sample replicated the previous finding that patient beliefs regarding necessity and concern were associated with poor adherence to prescribed medications. Polypharmacy had an additive role decreasing adherence in both samples. In both samples, when prescribed ≥4 psychiatric medications, patients reported adherence to only two-third of the medications.