The neurobiology of treatment-resistant schizophrenia: paths to antipsychotic resistance and a roadmap for future research

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Abstract

Treatment-resistant schizophrenia (TRS), the persistence of positive symptoms despite ≥2 trials of adequate dose and duration of antipsychotic medication with documented adherence, is a serious clinical problem with heterogeneous presentations. TRS can vary in its onset (at the first episode of psychosis or upon relapse), in its severity, and in the response to subsequent therapeutic interventions (i.e., clozapine, electroconvulsive therapy). The heterogeneity of TRS indicates that the underlying neurobiology of TRS may differ not only from treatment-responsive schizophrenia but also among patients with TRS. Several hypotheses have been proposed for the neurobiological mechanisms underlying TRS, including dopamine supersensitivity, hyperdopaminergic and normodopaminergic subtypes, glutamate dysregulation, inflammation and oxidative stress, and serotonin dysregulation. Research supporting these hypotheses is limited in part by variations in the criteria used to define TRS, as well as by the biological and clinical heterogeneity of TRS. Clinical trial designs for new treatments should be informed by this heterogeneity, and further clinical research is needed to more clearly understand the underlying neurobiology of TRS and to optimize treatment for patients with TRS.

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Meta-analysis of cytokine alterations in schizophrenia: clinical status and antipsychotic effects.

Brian Miller, Peter Buckley, Wesley Seabolt … (2011)

Schizophrenia is associated with immune system dysfunction, including aberrant cytokine levels. We performed a meta-analysis of these associations, considering effects of clinical status and antipsychotic treatment following an acute illness exacerbation. We identified articles by searching PubMed, PsychInfo, and Institute for Scientific Information and the reference lists of identified studies. Forty studies met the inclusion criteria. Effect sizes were similar for studies of acutely relapsed inpatients (AR) and first-episode psychosis (FEP). Interleukin (IL)-1β, IL-6, and transforming growth factor-β (TGF-β) appeared to be state markers, as they were increased in AR and FEP (p < .001 for each) and normalized with antipsychotic treatment (p < .001, p = .008, and p = .005, respectively). In contrast, IL-12, interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and soluble IL-2 receptor (sIL-2R) appeared to be trait markers, as levels remained elevated in acute exacerbations and following antipsychotic treatment. There was no difference in IL-6 levels between stable medicated outpatients and control subjects (p = .69). In the cerebrospinal fluid, IL-1β was significantly decreased in schizophrenia versus controls (p = .01). Similar effect sizes in AR and FEP suggest that the association between cytokine abnormalities and acute exacerbations of schizophrenia is independent of antipsychotic medications. While some cytokines (IL-1β, IL-6, and TGF-β) may be state markers for acute exacerbations, others (IL-12, IFN-γ, TNF-α, and sIL-2R) may be trait markers. Although these results could provide the basis for future hypothesis testing, most studies did not control for potential confounding factors such as body mass index and smoking. Copyright © 2011 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

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Treatment-Resistant Schizophrenia: Treatment Response and Resistance in Psychosis (TRRIP) Working Group Consensus Guidelines on Diagnosis and Terminology.

Oliver Howes, Rob McCutcheon, Ofer Agid … (2017)

Research and clinical translation in schizophrenia is limited by inconsistent definitions of treatment resistance and response. To address this issue, the authors evaluated current approaches and then developed consensus criteria and guidelines.

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Antipsychotic drugs versus placebo for relapse prevention in schizophrenia: a systematic review and meta-analysis.

Stefan Leucht, Magdolna Tardy, Katja Komossa … (2012)

Relapse prevention with antipsychotic drugs compared with placebo in patients with schizophrenia has not been sufficiently addressed by previous systematic reviews. We aimed to assess the association between such drugs and various outcomes in patients with schizophrenia to resolve controversial issues. We searched the Cochrane Schizophrenia Group's specialised register for reports published before Nov 11, 2008; and PubMed, Embase, and ClinicalTrials.gov for those before June 8, 2011. We also contacted pharmaceutical companies and searched the reference lists of included studies and previous reviews. Randomised trials of patients with schizophrenia continued on or withdrawn from any antipsychotic drug regimen after stabilisation were eligible. Our primary outcome was relapse between 7 and 12 months. We also examined safety and various functional outcomes. We used the random effects model and verified results for the primary outcome with a fixed effects model. Heterogeneity was investigated with subgroup and meta-regression analyses. We identified 116 suitable reports from 65 trials, with data for 6493 patients. Antipsychotic drugs significantly reduced relapse rates at 1 year (drugs 27%vs placebo 64%; risk ratio [RR] 0·40, 95% CI 0·33-0·49; number needed to treat to benefit [NNTB] 3, 95% CI 2-3). Fewer patients given antipsychotic drugs than placebo were readmitted (10%vs 26%; RR 0·38, 95% CI 0·27-0·55; NNTB 5, 4-9), but less than a third of relapsed patients had to be admitted. Limited evidence suggested better quality of life (standardised mean difference -0·62, 95% CI -1·15 to -0·09) and fewer aggressive acts (2%vs 12%; RR 0·27, 95% CI 0·15-0·52; NNTB 11, 6-100) with antipsychotic drugs than with placebo. Employment data were scarce and too few deaths were reported to allow significant differences to be identified. More patients given antipsychotic drugs than placebo gained weight (10%vs 6%; RR 2·07, 95% CI 2·31-3·25), had movement disorders (16%vs 9%; 1·55, 1·25-1·93), and experienced sedation (13%vs 9%; 1·50, 1·22-1·84). Substantial heterogeneity in size of effect was recorded. In subgroup analyses, number of episodes, whether patients were in remission, abrupt or gradual withdrawal of treatment, length of stability before trial entry, first-generation or second-generation drugs, and allocation concealment method did not significantly affect relapse risk. Depot preparations reduced relapse (RR 0·31, 95% CI 0·21-0·41) more than did oral drugs (0·46, 0·37-0·57; p=0·03); depot haloperidol (RR 0·14, 95% CI 0·04-0·55) and fluphenazine (0·23, 0·14-0·39) had the greatest effects. The effects of antipsychotic drugs were greater in two unblinded trials (0·26, 0·17-0·39) than in most blinded studies (0·42, 0·35-0·51; p= 0·03). In a meta-regression, the difference between drug and placebo decreased with study length. Maintenance treatment with antipsychotic drugs benefits patients with schizophrenia. The advantages of these drugs must be weighed against their side-effects. Future studies should focus on outcomes of social participation and clarify the long-term morbidity and mortality of these drugs. German Ministry of Education and Research. Copyright © 2012 Elsevier Ltd. All rights reserved.