Researchers at the Centre for Addiction and Mental Health in Toronto characterized a cohort of people with schizophrenia who had enrolled in a genetics study. In this convenience sample of 478 subjects, 156 were considered treatment resistant (TR) according to American Psychiatric Association guidelines. The APA guidelines define treatment resistance as “little or no symptomatic response to multiple (at least two) antipsychotic trials of an adequate duration (at least 6 weeks) and dose (therapeutic range).”
The investigators found no correlation between treatment resistance and sex; family history of psychosis; schizophrenia subtype; cannabis, alcohol or drug use; or number of cigarettes consumed daily. However, the TR patients had been ill for a mean of 21 years compared with 15 years for the non-TR group (P < .001). Among patients identified as having white European ancestry, 37% were TR, whereas 18% of nonwhites were TR (P =.03). Several treatment factors were significantly correlated with treatment resistance. In the TR group, 33% were on clozapine compared with 13.3% in the non-TR group, and 25% of TR patients were on more than one antipsychotic, double the rate in the non TR group. Ten percent of the TR patients were on clozapine and at least one other antipsychotic. Furthermore, the TR patients had a mean of 3 failed medication trials, whereas the non-TR patients had a mean of 0.5 failed trials. This nonrandom sample is not necessarily representative of all TR patients, so the significance of the lower rate among non-white patients is unclear. The study corroborates previous research indicating that treatment resistance occurs in chronic patients, and that polypharmacy is used possibly at the expense of clozapine. References Teo C, Borlido C, Kennedy JL, De Luca V. The role of ethnicity in treatment refractory schizophrenia. Compr Psychiatry. 2013;54(2):167-172. Link to abstract.