Adherence to Antipsychotic Medication and Criminal Recidivism in a Canadian Provincial Offender Population

Preliminary evidence suggests that adherence to antipsychotic medication reduces criminal recidivism among patients diagnosed with schizophrenia. However, existing studies operationalize antipsychotic adherence as a binary variable (usually using a threshold of >= 80%), which does not reflect the prevalence of suboptimal adherence in realworld settings. The purpose of the current analysis was to investigate the association between successive ordinal levels of antipsychotic adherence and criminal recidivism in a well-defined sample of offenders diagnosed with schizophrenia (n = 11 462). Adherence was measured using the medication possession ratio (MPR) and analyzed as a timedependent covariate in multivariable regression models. Data were drawn from linked, comprehensive diagnostic, pharmacy and justice system records, and individuals were followed for an average of 10 years. Adjusted rate ratios (ARR) and confidence intervals (CI) are reported. Overall mean MPR was 0.41. Increasing levels of antipsychotic adherence were not associated with progressively lower rates of offending. However, when compared to the reference group (MPR >= 80%) all lower adherence levels were significantly associated (P <.001) with increased risk of violent (ARR = 1.58; 95% CI = 1.46-1.71) and nonviolent (ARR = 1.41; 95% CI = 1.33-1.50) offenses. Significance was replicated in separate sensitivity analyses. Previously published studies reporting reductions in crime may have been influenced by antipsychotic adherence >= 80%. Binary operationalization of adherence is an inaccurate predictor of recidivism. Future research addressing functional outcomes of antipsychotic adherence should conceptualize adherence as an incremental independent variable.