Medication Adherence and Long-Term Functional Outcomes in the Treatment of Schizophrenia in Usual Care

Abstract

BACKGROUND: Relatively little is known about the relationships between medication adherence and long-term functional outcomes in the treatment of schizophrenia. To extend previous research, we prospectively examined the relationships between adherence with any antipsychotic medication and functional outcomes among schizophrenia patients treated over a 3-year period, assessed the stability of adherence over time, and examined whether adherence in the first year predicts changes in functional outcomes over the following 2 years. METHOD: Analyses included 1906 participants with DSM-IV diagnoses of schizophrenia or schizoaffective or schizophreniform disorder in a multi-site, 3-year, prospective, naturalistic study conducted in the United States between July 1997 and September 2003. Outcome measures were assessed at 6-month intervals using systematic medical record abstraction and structured interview of patients. Adherence with antipsychotic regimen was assessed using patient-reported adherence and the medication possession ratio (percent days with prescription for any antipsychotic), dichotomized into adherence and non-adherence. Analyses employed generalized estimating equations and mixed models with repeated measures. RESULTS: Nonadherence was associated with poorer functional outcomes, including greater risks of psychiatric hospitalizations, use of emergency psychiatric services, arrests, violence, victimizations, poorer mental functioning, poorer life satisfaction, greater substance use, and more alcohol-related problems (all p < .001). Adherence was relatively stable, with 77.3% of patients maintaining the same adherence status from the first year to the second year. Nonadherence in the first year predicted significantly poorer outcomes in the following 2 years. CONCLUSIONS: Findings highlight the importance of adherence with antipsychotic medication in the long-term treatment of schizophrenia and its potential beneficial impact on the mental health and criminal justice delivery systems.