Abstract
BACKGROUND: Among individuals with schizophrenia, antipsychotic medications improve performance across several cognitive and functional domains. We sought to assess whether antipsychotic adherence reduces the risk of a motor vehicle crash. METHODS: We performed a case-crossover study using population-based administrative health and driving data from British Columbia, Canada. We included individuals with schizophrenia who were involved as a driver in a police-attended motor vehicle crash during a 15-year interval (2001-2016) and who filled prescriptions for antipsychotic medication as an outpatient in the 2 years before the crash. We measured adherence to antipsychotic treatment by using prescription fill data to calculate the medication possession ratio (MPR) in the 30 days before the crash (the pre-crash interval) and in a 30-day control interval ending 1 year before the crash. We used conditional logistic regression to evaluate the association between MPR and motor vehicle crash after adjusting for potential confounders. RESULTS: Among 1130 eligible motor vehicle crashes involving drivers with schizophrenia, the mean antipsychotic MPR was 0.69 in the pre-crash intervals and 0.76 in the control intervals. We found that perfect adherence to antipsychotic medication was associated with half the odds of a crash relative to complete nonadherence (adjusted odds ratio 0.50, 95% confidence interval 0.38-0.66). The findings were consistent among subgroups defined by sex, age, and history of alcohol or drug misuse. INTERPRETATION: Better adherence to antipsychotic medications was associated with lower crash risk. Physicians and fitness-to-drive policy-makers might consider antipsychotic treatment adherence as a condition for maintaining an active driver's licence among individuals with schizophrenia.