The role of ethnicity in treatment refractory schizophrenia

ObjectiveThe goal of this research was to describe the relationship between treatment resistant schizophrenia, defined using the APA criteria and ethnic background in patients with schizophrenia spectrum disorders in a Canadian sample. A secondary goal was to analyze the number of antipsychotics failed due to side effects and number of antipsychotics failed due to non-response.MethodWe included 497 patients diagnosed with schizophrenia spectrum disorders using the SCID. The medication history was extracted from the electronic health records. Data collection included demographics (sex, age, ethnicity), principal diagnosis according to SCID (Diagnostic and Statistical Manual of Mental Disorders, 4th edition), duration of mental illness, number of psychiatric admissions and treatment information. If patients were on clozapine or polypharmacy treatment, this was recorded at the time of the SCID interview. Additional data, including prior antipsychotic history, were collected from the health records.ResultsThirty per cent of the patients were classified as resistant according to the APA criteria. There were significantly more white European subjects in the treatment resistant group (p = 0.031). The duration of illness was significantly higher in the resistant group then in the non-resistant group (21.0 vs 15.1 years; p < 0.001). Patients who were treatment resistant were more likely to be on polypharmacy compared with non-resistant patients (p = 0.001; OR = 2.424; 95%CI = 1.446-4.065). When we considered the number of drug trials failed due to non response and drug trial failed because of side effects, we found a strong negative correlation in both white Europeans and non-white Europeans.ConclusionsWhite European ethnicity is associated with treatment resistant schizophrenia. In addition, patients with treatment-resistant schizophrenia were on polypharmacy at higher rate than non resistant patients.