OBJECTIVES: Several studies have estimated health state utilities for patients with schizophrenia according to disease stage. However, the quality of life of these patients is also largely dependent on treatment-related adverse events, and there is paucity of data on utilities associated with those adverse events. The objective of this study was to estimate utility decrements associated with treatment-related adverse events in patients with schizophrenia, using data from an observational study. METHODS: We used data from EuroSC, a multicenter 2-year cohort study conducted in France, England and Germany. The EQ-5D questionnaire was completed every 6 months, as well as the Subjective Side Effect Rating Scale, assessing patient distress over extrapyramidal symptoms, weight gain, sedation and sexual dysfunction over the past seven days. A random-effects regression analysis was used to estimate the impact of these adverse events on utilities with adjustment on disease severity and other potential confounding factors. RESULTS: Our sample consisted in 1208 patients with schizophrenia. At baseline, the mean EQ-5D utility was 0.73 (0.28), 57.7% of patients reported extrapyramidal symptoms, 46.2% weight gain, 46.5% sedation and 27.8% sexual dysfunction. The regression model showed that extrapyramidal symptoms, weight gain, sedation and sexual dysfunction were associated with reductions in utility of 0.054 (0.008), 0.018 (0.008), 0.021 (0.008) and 0.032 (0.011) points, respectively. CONCLUSIONS: This study shows that side effects are associated with significant decrements in EQ-5D utility, especially extrapyramidal symptoms. Additionally, adverse events may have an indirect negative impact on quality of life, since they may be associated with reduced treatment adherence, and therefore reduced treatment effectiveness.