To assess baseline predictors and consequences of antipsychotic adherence during the long-term treatment of schizophrenia outpatients, data were taken from the 3-year, prospective, observational, European Schizophrenia Outpatients Health Outcomes (SOHO) study, in which outpatients starting or changing antipsychotics were assessed every 6 months. Physician-rated adherence was dichotomized as adherence/non-adherence. Regression models tested for predictors of adherence during follow-up, and associations between adherence and outcome measures. Of the 6731 patients analysed, 71.2% were adherent and 28.8% were non-adherent over 3 years. The strongest predictor of adherence was adherence in the month before baseline assessment. Other baseline predictors of adherence included initial treatment for schizophrenia and greater social activities. Baseline predictors of non-adherence were alcohol dependence and substance abuse in the previous month, hospitalization in the previous 6 months, independent housing and the presence of hostility. Non-adherence was significantly associated with an increased risk of relapse, hospitalization and suicide attempts. In conclusion, non-adherence is common but can partly be predicted. This may allow strategies to improve adherence to be targeted to high-risk patients. Also, reversal of some risk factors may improve adherence. Non-adherence is associated with a range of poorer long-term outcomes, with clinical and economic implications.
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