Patients with schizophrenia are at heightened risk for being resistant to treatment if they are White European, study findings reveal.
"The cause of this association could be mainly cultural," say Vincenzo De Luca and colleagues, from the University of Toronto in Ontario, Canada.
"Most studies involving access to care have shown significant ethnic differences in relation to social factors, which include employment, living situation, family support, or general practitioner involvement," they explain.
"These factors affecting pathways to care have shown to be vital indicators of duration of untreated psychosis."
The team assessed treatment response in 497 patients diagnosed with schizophrenia spectrum disorders. Medication history was obtained from medical health records.
In all, 30% of the patients were classified as treatment resistant according to the American Psychiatric Association criteria, which states that a patient is treatment refractory when they have little or no symptomatic response to multiple (at least two) antipsychotic trials within an adequate duration (at least 6 weeks) and with an adequate dose within the therapeutic range.
When stratified according to ethnicity, 36.7% of White Europeans were resistant to treatment, compared with 19.1% of non-White Europeans. This means that being of White-European ethnicity conveys a 1.78-fold increased risk for treatment resistance, the team reports in Comprehensive Psychiatry.
By contrast, neither gender nor a positive family history for psychiatric disorders were significantly associated with treatment resistance.
Patients who were resistant to treatment had a significantly longer duration of illness than those who were not resistant, at 21 versus 15 years, and there was a significant association between a high number of hospitalizations and non-resistant status.
Treatment-resistant patients were also more likely to be receiving clozapine treatment (odds ratio [OR]=2.9), polypharmacy treatment (OR=2.4), and a combination of clozapine and polypharmacy (OR=3.8).
The researchers comment that previous research has shown that African-American patients with psychotic disorders receive higher doses of antipsychotic medications than White patients, and are more likely to receive depot antipsychotics and less likely to be prescribed second-generation antipsychotics despite no evidence of a difference in clinical severity or a need for higher therapeutic doses.
"There is a possibility that because African-American patients are prescribed higher doses and given depot medications they have a lower chance of developing resistance as compared to white Europeans," they suggest.
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