The impact of non-adherence to medication in patients with schizophrenia on health, social care and societal costs: analysis of the QUATRO study Article (Accepted version) (Refereed) Original citation: Title: The impact of non-adherence to medication in p

This document is the author's final accepted version of the journal article. There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it. 1 Title: The impact of non-adherence to medication in patients with schizophrenia on health, social care and societal costs -analysis of the QUATRO study Methods: Data were taken from QUATRO, a randomized controlled trial that drew a sample of adults with schizophrenia receiving psychiatric services in four European cities: Amsterdam, Leipzig, London and Verona. Trial inclusion criteria were a clinical diagnosis of schizophrenia, requiring on-going antipsychotic medication for at least one year following baseline assessment, and exhibiting evidence of clinical instability in the year prior to baseline. The patient-completed Medication Adherence Questionaire (MAQ) was used to calculate the 5-point Morisky index of adherence. Generalised linear models were developed to determine the effect of adherence on (i) health and social care and (ii) societal costs before and after treatment, taking into account other potential cost-influencing factors. Results: The effect of non-adherence on costs was mixed. For different groups of services, and according to treatment group assignment, non-adherence was both negatively and positively associated with costs. Conclusions: The impact of non-adherence on costs varies across the types of services used by individuals with schizophrenia.