Elsevier

Comprehensive Psychiatry

Volume 54, Issue 2, February 2013, Pages 167-172
Comprehensive Psychiatry

The role of ethnicity in treatment refractory schizophrenia

https://doi.org/10.1016/j.comppsych.2012.07.002Get rights and content

Abstract

Objective

The 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.

Method

We 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.

Results

Thirty 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.

Conclusions

White 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.

Introduction

Schizophrenia is prevalent in about 1% of the general population. This means that more than one million people in North America are diagnosed with schizophrenia.

Within these numbers, there is an estimation of about 20 to 40% of individuals who are resistant to treatment. Even with the introduction of several second-generation antipsychotic medications, the numbers still remain stable [1], [2], [3], [4]. It is generally accepted that within the population at risk, 10 to 60% of patients responds poorly or only partially to treatment [1], [3], [5], [6]. Even with compliance to medications, 20 to 30% of patients will still suffer a relapse in the first or second year of maintenance treatment with antipsychotics [3], [7]. Since these patients remain symptomatic, there is a cumulative increase in the number of patients who are resistant to antipsychotic treatment [8], [9], [10], [11]. This depicts a significant public health problem. Individuals with treatment resistant schizophrenia typically have longer hospitalizations, are low functioning when out in the community and 80 to 90% of them develops some kind of social or occupational dysfunction [12], [13].

There have been multiple debates over the criteria of treatment-resistance. There are operational definitions, the most widely used are those by Kane et al. [7] which are three-dimensional (historical, current, or psychopathological and prospective). The historical definition stating that “at least 3 treatments with antipsychotics of at least 2 different chemical classes with doses equivalent to 1,000 mg/day of chlorpromazine for a period of 6 weeks, without significant improvement and no period of good functioning within the preceding 5 years”. The current/psychopathological criterion is “a score of ≥45 in the BPRS, with scores of ≥4 in 2 of the following items: conceptual disorganization, suspiciousness, hallucinatory behaviour or unusual thought content and CGI ≥4 (moderately ill). Finally, the prospective criteria indicates “no improvement after 6 weeks of treatment with haloperidol (≤60 mg/day), defining improvement as a reduction of at least 20% in the BPRS total score.

Both genetic and environmental factors influence resistance to antipsychotic medications, however the specific interaction between them is unknown. Clinical and social factors related to the efficacy of treatment include compliance, family support, milder psychotic symptoms, better attention at baseline, few obstetric complications, later age of onset, and duration of illness less than nine years [14], [15], [16]. In addition, the lack of early treatment in ethnic minorities, is also a contributing factor to eventual resistance to antipsychotics.

However, a study conducted by Archie et al. on the ethnic diversity and pathways to care in Ontario shows that there was no ethnic differences for duration of untreated psychosis [20]. The fact that Ontario has a public healthcare system seems to explain the lack of biasness towards any group of individuals who seeks help for mental health treatment.

Cantor-Graae and Selten [21] conducted a meta-analysis of incidence rate of schizophrenia, combining 18 studies from different countries. Their findings showed a three times increased risk for schizophrenia in first- and second-generation migrants as compared to non-migrants. The same study showed higher risk in second-generation migrants and in migrants from developing countries and from countries where the majority of the population is black.

Despite the fact that there are publications on the schizophrenia risk in ethnic minorities little is known about resistance to antipsychotics in different ethnicities. The aim of this work is to explore ethnic effect in treatment refractory schizophrenia. The secondary aim is to test whether treatment resistance is associated with clinical variables in our sample.

Section snippets

Methods

In this study, subjects were either referred by staff clinicians or responded to advertisements. Patients over the age of 18 years who satisfied the DSM-IV diagnostic criteria for schizophrenia or schizoaffective disorder (depressive subtype only) were included, while patients with history of major neurological disorders, head injury with significant loss of consciousness, or major substance abuse were excluded from the study.

The sample comprised 497 patients assessed using a structure

Treatment resistance and clinical variables

According to the SCID in our sample (n = 497) there were 19 patients with schizoaffective disorder and 478 with schizophrenia (297 with paranoid subtype).

According to our review 156 were classified as resistant and 337 were classified as non-resistant. Four patients were excluded from the analysis after the consensus conference because the resistant status was unclear.

Duration of illness was significantly longer in the resistant group (21.0 vs 15.1 years; p < 0.001) and when we applied the

Discussion

The primary aim of this study was to explore the role of ethnicity in influencing the treatment resistance in schizophrenia and the main finding was that white European ethnicity is a risk factor for treatment resistant schizophrenia. The cause of this association could be mainly cultural in fact 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

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