In treatment-resistant schizophrenia, clozapine treatment has been associated with longitudinal reductions in subcortical volumes, ventricular enlargement, and widespread cortical thinning. However, it is unknown how these structural changes relate to clozapine's pharmacological profile and clinical efficacy. We combined five longitudinal datasets with MRI acquired before and on average 5 months after clozapine initiation in 143 individuals to quantify brain structural changes and their association with normative maps relating to neuroreceptor architecture and physiological systems, and improvement in symptom severity. Clozapine treatment was associated with grey matter volume reductions across multiple subcortical regions (including the amygdala, hippocampus, thalamus, caudate, putamen and nucleus accumbens), increases in pallidal volume, ventricular enlargement, and widespread cortical thinning. Cortical regions showing the greatest magnitude of thinning corresponded to areas with higher normative densities of serotonergic 5-HT1A, 5-HT2A and 5-HT4 receptors. Changes in subcortical volume or cortical thickness during clozapine treatment were not associated with changes in total or positive symptom severity. In addition, baseline subcortical volume, cortical thickness, or gyrification prior to starting clozapine did not predict subsequent symptom improvement. Cortical thinning may partly reflect clozapine's activity at serotonergic receptors, which have been implicated in cortical network stabilisation and neuroplasticity, however structural remodelling during clozapine treatment may reflect a process independent from its clinical efficacy in improving core symptoms of psychosis.

BACKGROUND:Treatment-resistant schizophrenia (TRS) is associated with alterations in glutamate levels and cerebral blood flow (CBF), and treatment with clozapine appears to have an impact on each of these measures. Here, we examined whether changes in CBF and glutamate levels following clozapine treatment are related. METHODS:Glutamate concentrations in the anterior cingulate cortex (ACC), and striatum (measured using proton magnetic resonance spectroscopy, 1H-MRS); and whole brain regional CBF maps (measured using pseudo-continuous arterial spin labelling (pCASL)), were examined in a cohort of TRS subjects before and after 12 weeks of treatment with clozapine (baseline: N = 30; week 12: N = 20). RESULTS:The longitudinal change in striatal glutamate during treatment was positively associated with the longitudinal change in striatal CBF (p < 0.05). In the ACC, higher Glx (glutamate + glutamine) and CBF prior to treatment were associated with greater subsequent improvement in total symptom severity. CONCLUSIONS:These results indicate that there is a direct relationship between changes in glutamate activity and CBF in the striatum following clozapine treatment. Future research could investigate whether glutamate-CBF relationships exist in other stages of psychosis or schizophrenia and during treatment with other antipsychotic medications. Associations with clinical outcomes could be explored in larger samples.

Clozapine may have both pro- and anti-inflammatory effects, which could contribute to its unique efficacy in treatment resistant schizophrenia (TRS). Increases in pro-inflammatory cytokines occur during the first weeks after clozapine initiation, but the changes occurring over longer periods of clozapine administration are largely unknown.This study examined C-reactive protein (CRP), tumour necrosis factor alpha (TNF-α), interferon-gamma (IFN-γ), and interleukins (IL) IL-2, IL-4, IL-6, IL-8, IL-12p70 and IL-13 prior to clozapine titration (baseline) and after 3 and 6 months of clozapine treatment in TRS. Symptom severity was assessed at the same time-points.Data were available in 53 individuals at baseline, 34 individuals at 3 months and 28 individuals at 6 months. Following correction for false discovery rate (FDR): significant effects of time were observed for IL-10 (F(2, 67.7) = 9.15, P < 0.001, q = 0.010) and TNF-α (F(2, 58.9) = 5.67, P = 0.006; q = 0.030), related to significant increases in both IL-10 and TNF-α at 3 and 6 months after commencing clozapine compared to at baseline (α = 0.05). There were no significant associations between temporal changes in peripheral inflammatory marker concentrations and changes in total symptom severity, or relationships between inflammatory marker concentrations at baseline and total symptom severity at 3 months.Concurrent increases in TNF-α and IL-10 may reflect increased activation of both pro-inflammatory and compensatory anti-inflammatory mechanisms over 6 months of clozapine treatment. Composite indices of inflammatory profile may be advantageous in future studies examining relationships with symptom improvement during clozapine treatment.

Clozapine is the only effective treatment for treatment-resistant schizophrenia, but concerns over blood dyscrasia and need for monitoring limit its use. Evidence suggests many hematological abnormalities may result from surveillance bias, with agranulocytosis being the primary adverse effect directly induced by clozapine. This systematic review (PROSPERO: CRD42024487199) investigates non-genetic risk factors associated with blood dyscrasia during clozapine treatment, focusing on neutropenia and agranulocytosis. Random-effect meta-analyses were performed on studies reporting quantitative risk data. Due to inconsistent neutropenia definitions, analyses used absolute neutrophil count (ANC) thresholds of <2000/mm3, <1500/mm3, and <500/mm3. Forty-four studies were included in the systematic review, 15 in meta-analyses. No significant association was found between agranulocytosis and female gender (OR = 1.48, 95% CI: 0.92-2.38; p = 0.106) or age (pooled standardized mean difference [SMD] = 0.32, 95% CI: -0.26 to 0.90, p = 0.285), whilst a modest inverse association with clozapine dose (SMD = -0.32, 95%CI: -0.50 to -0.14, p < 0.001) and baseline white cell count (SMD = -0.21, 95%CI: -0.40 to -0.03, p = 0.026) was found. Neutropenia (ANC < 2000/mm3) was positively associated with concomitant psychotropic use (OR = 2.15, 95% CI: 1.13-4.07, p = 0.019). Clozapine rechallenge studies revealed no significant associations with gender, age, duration of initial clozapine trial, or length of discontinuation period prior to rechallenge. No strong predictors of clozapine-associated blood dyscrasia were identified. Findings may be limited by study variability, surveillance bias, and lack of consistent differentiation between agranulocytosis and milder neutropenia, highlighting limitations in current evidence.

Schizophrenia trials have been too small, short and exclusionary, leaving the most disabled patients under-represented and key outcomes neglected. Future research should match the illness burden through sustained funding, representative recruitment, multidomain assessment, and adaptive, platform and SMART designs that test treatments efficiently and produce evidence relevant to patients' lives.

In about a quarter of people with schizophrenia-spectrum disorder (SSD), the illness is unresponsive to standard antipsychotic treatment, yet the biological mechanisms underlying this remain poorly understood. Although such treatment-resistant schizophrenia (TRS) shares a substantial genetic liability with treatment-responsive schizophrenia, the limited efficacy of dopamine antagonists in TRS indicates that mechanisms beyond dopamine signalling likely contribute to treatment-resistance, requiring the identification of alternative biological pathways. This is the first cross-ancestry genetic study to investigate the genetic architecture of TRS, by directly comparing patients with treatment-resistant and treatment-responsive schizophrenia in two independent Hong Kong (N=798) and STRATA-G consortium (N=1243) cohorts. Using an integrated multi-level analytic framework, we conducted a genome-wide association study (GWAS) with gene-based and gene set-based analyses, pathway polygenic-risk-scores, and transcriptome-wide association study (TWAS). We further conducted gene-set enrichment analysis focusing on expert-curated synaptic pathways and brain tissues. Genetic signals at the gene, pathway, and genetically predicted expression levels were identified within each ancestry. Whereas limited power constrained individual loci discovery and cross-ancestry concordance, enrichment analyses indicated heterogeneous signals across cohorts, including differences in effect direction, but highlighted cohort-specific, synapse-related biology, particularly pathways involved in presynaptic vesicle dynamics, neurotransmission, and synaptic organization. Collectively, these findings highlight synaptic biology as one potential pathway-level signal from common-variant genetic effects associated with treatment resistance in SSD, despite minimal SNP-level discovery. Our work suggests there is promise in pathway-level and multi-omics approaches to elucidate biologically meaningful heterogeneity within SSD and provides support for synaptic mechanisms as potential targets for understanding and stratifying treatment-resistance.

A great deal is known about the use, benefits, and side effects of clozapine in treatment-resistant schizophrenia (TRS). However, why clozapine is more effective than other antipsychotics in TRS remains unclear. In this article, we address this question. Patients with TRS show glutamate abnormalities, and clozapine has widespread effects on glutamate. However, these actions have not been proven to be different from those of other antipsychotics. Immune dysfunction is also reported in TRS, and clozapine has anti-inflammatory actions, but these have not been correlated with clinical improvement. Currently, there is a great deal of interest in muscarinic abnormalities in psychosis. Unlike most antipsychotics, clozapine has important effects on muscarinic receptors, particularly M1 and M4, and its major metabolite, N-desmethylclozapine, is a full agonist at M1. These effects are likely crucial to clozapine's effectiveness. In addition, clozapine's lower dopamine D2 receptor occupancy has been postulated to allow gradual resolution of dopamine receptor supersensitivity in the minority of patients with TRS who initially respond to antipsychotics but become resistant following long-term dopamine blockade. However, this hypothesis remains controversial. Clozapine's multireceptor profile enables it to have beneficial actions on the nonpsychotic symptoms common in TRS; its ability to bind to histamine H1, serotonin 5-HT1A, and GABAB (gamma-aminobutyric acid B) receptors offers an explanation for its anxiolytic actions, while effects on 5-HT1A, 5-HT2A, and 5-HT7 receptors likely underlie its antidepressant properties. Clozapine shares these properties with olanzapine and quetiapine, but its affinity for muscarinic receptors may be the mechanism by which it is more effective in TRS.

Background The immune system may play an important role in the aetiology of psychotic disorders and there is increasing interest in the relationship between immune markers and clinical outcomes in psychosis. The present study investigated whether subclinical systemic inflammation was associated with length of stay in individuals with psychosis admitted to a psychiatric hospital. We tested the hypothesis that a higher level of subclinical systemic inflammation, as measured by the neutrophil-to-lymphocyte ratio (NLR) would be associated with a longer period in hospital. Method Retrospective cohort study based on electronic health records. We included patients with a psychosis spectrum disorder (ICD10: F20-F29) who had a routine blood test upon being admitted to a psychiatric hospital within the South London and Maudsley NHS Foundation Mental Health Trust, London, UK between 2013 and 2019. Multiple linear regression was used to determine the association between the NLR at the time of admission and the duration of the corresponding hospital stay, adjusting for covariables. Results Data from 1683 individuals with psychosis were analyzed. The median admission duration was 31 days (interquartile range = 48 days). Higher neutrophil-to-lymphocyte ratio (NLR) was significantly associated with longer admission (B = 0.07, p < 0.003) after adjusting for covariates. Conclusion An association between a NLR and a longer admission, whilst controlling for relevant covariables, was observed highlighting the potential utility of inflammatory markers as prognostic marker in clinical settings.

Recent years have seen a proliferation of interest in psychological networks, which conceptualise psychopathology as networks of inter-connected, mutually reinforcing symptoms. It has been hypothesised that the topological structure of such networks is associated with clinical presentation. Analysing data from a longitudinal study of participants diagnosed with psychosis, we identify substantial inter-individual variability in network structure, problematising causal inference from cross-sectional networks. Additionally, we do not find strong evidence for an association between network structure and clinical relapse.

BACKGROUND:Clozapine is known to cause agranulocytosis. Mandatory monitoring schemes are aimed at reducing the risk of agranulocytosis and of the consequences of agranulocytosis. All cases of agranulocytosis occurring in people prescribed clozapine are assumed to be caused by clozapine. METHODS:In a previous study, we examined a cohort of patients listed on our hospital database as having had clozapine-induced agranulocytosis and applied specific criteria to identify those with confirmed clozapine-related, life-threatening agranulocytosis. In this study, we examine the cases not meeting these specific criteria. RESULTS:In the original study, 9 of 23 cases met the criteria for clozapine-induced, life-threatening agranulocytosis. Of the 13 remaining cases for whom data were available, 5 were probably caused by clozapine but were not life-threatening. Three cases were the result of concomitant cancer chemotherapy. Three were anomalous results probably related to measurement error. For the remaining two cases, the cause was not identified. CONCLUSION:Not all cases of agranulocytosis occurring in people taking clozapine are caused by clozapine. The widely used threshold criterion-based diagnosis overestimates the risk of agranulocytosis. True clozapine-related agranulocytosis is best identified by pattern-based criteria: rapid fall in neutrophil counts over around 2 weeks to below 0.5 × 109/L for two consecutive days (unless clozapine is stopped very early or granulocyte colony stimulating factor is given) where other possible causes (benign ethnic neutropenia, cancer chemotherapy) can be ruled out.

Background Clozapine is an antipsychotic drug with unique efficacy, and it is the only recommended treatment for treatment-resistant schizophrenia (TRS: failure to respond to at least two different antipsychotics). However, clozapine is also associated with a range of adverse effects which restrict its use, including blood dyscrasias, for which haematological monitoring is required. As treatment resistance is recognised earlier in the illness, the question of whether clozapine should be prescribed in children and young people is increasingly important. However, most research to date has been in older, chronic patients, and evidence regarding the efficacy and safety of clozapine in people under age 25 is lacking. The CLEAR (CLozapine in EARly psychosis) trial will assess whether clozapine is more effective than treatment as usual (TAU), at the level of clinical symptoms, patient rated outcomes, quality of life and cost-effectiveness in people below 25 years of age. Additionally, a nested biomarker study will investigate the mechanisms of action of clozapine compared to TAU. Methods and design This is the protocol of a multi-centre, open label, blind-rated, randomised controlled effectiveness trial of clozapine vs TAU (any other oral antipsychotic monotherapy licenced in the British National Formulary) for 12 weeks in 260 children and young people with TRS (12–24 years old). Aim and objectives The primary outcome is the change in blind-rated Positive and Negative Syndrome Scale scores at 12 weeks from baseline. Secondary outcomes include blind-rated Clinical Global Impression, patient-rated outcomes, quality of life, adverse effects, and treatment adherence. Patients will be followed up for 12 months and will be invited to give consent for longer term follow-up using clinical records and potential re-contact for further research. For mechanism of action, change in brain magnetic resonance imaging (MRI) biomarkers and peripheral inflammatory markers will be measured over 12 weeks. Discussion The CLEAR trial will contribute knowledge on clozapine effectiveness, safety and cost-effectiveness compared to standard antipsychotics in young people with TRS, and the results may guide future clinical treatment recommendation for early psychosis. Trial registration ISRCTN Number: 37176025, IRAS Number: 1004947. Trial status In set-up. Protocol version 4.0 01/08/23. Current up to date protocol available here: https://fundingawards.nihr.ac.uk/award/NIHR131175# /.

AimsThe association of assault in adulthood with all-cause mortality, and the relevance of intermediate psychological distress, alcohol use and cigarette smoking, is poorly understood. We used data from British birth cohorts (the 1958 National Child Development Study referred to as the 1958 birth cohort and the 1970 British Birth Cohort Study) to investigate association between assault and mortality, employing a formal approach for the identification of psychological distress, alcohol use and cigarette smoking as mediators.MethodsAssociations (HRs), between assault and mortality were estimated with Cox regressions, adjusting for potential confounders. Mediation via intermediate psychological distress, alcohol use and cigarette smoking was explored using the gformula approach. The birth cohorts were analysed separately, and together estimating interaction between exposure and cohort year.ResultsResults were based on 353 deaths in 19 725 individuals. Based on multiply imputed data, the fully adjusted estimate for assault on mortality was 1.72 (95% CI 1.22 to 2.42) in the combined cohorts, 1.53 (95% CI 0.97 to 2.40) in the 1958 birth cohort and 2.05 (95% CI 1.20 to 1.50) in the 1970 birth cohort. The fully adjusted estimate for the association of sexual assault with mortality was 3.17 (95% CI 1.17 to 8.60) in the combined cohorts, 1.36 (95% CI 0.19 to 9.81) in the 1958 birth cohort and 6.02 (95% CI 1.84 to 19.69) in the 1970 birth cohort. The fully adjusted mortality HR for one additional assault was 1.46 (95% CI 1.23 to 1.73) in the combined cohorts, 1.34 (95% CI 0.99 to 1.82) in the 1958 birth cohort and 1.53 (95% CI 1.25 to 1.87) in the 1970 birth cohort. Greater need for medical treatment for assault was associated with a fully adjusted mortality HR of 1.56 (95% CI 1.19 to 2.05) in the combined cohorts, 1.43 (95% CI 1.00 to 2.05) in the 1958 birth cohort and 1.79 (95% CI 1.18 to 2.74) in the 1970 birth cohort.ConclusionsThere was statistical evidence on combining the two birth cohorts, and on analysing the 1970 birth cohort, that assault in adulthood is associated with mortality. Understanding mechanisms underlying this relationship could benefit violence reduction strategies for public health.

The second-generation antipsychotic clozapine is used as a medication for treatment-resistant schizophrenia. It has previously been associated with epigenetic changes in pre-clinical rodent models and cross-sectional studies of treatment-resistant schizophrenia. Cross-sectional studies are susceptible to confounding, however, and cannot disentangle the effects of diagnosis and medication. We therefore profiled DNA methylation in sequential blood samples (n = 126) from two independent cohorts of patients (n = 38) with treatment-resistant schizophrenia spectrum disorders who commenced clozapine after study enrolment and were followed up for up to six months. We identified significant non-linear changes in cell-type proportion estimates derived from DNA methylation data - specifically B-cells - associated with time on clozapine. Mixed effects regression models were used to identify changes in DNA methylation at specific sites associated with time on clozapine, identifying 37 differentially methylated positions (DMPs) (p < 5 x 10(-5)) in a linear model and 90 DMPs in a non-linear quadratic model. We compared these results to data from our previous epigenome-wide association study (EWAS) meta-analysis of psychosis, finding evidence that many previously identified DMPs associated with schizophrenia and treatment-resistant schizophrenia might reflect exposure to clozapine. In conclusion, our results indicate that clozapine exposure is associated with changes in DNA methylation and cellular composition. Our study shows that medication effects might confound many case-control studies of neuropsychiatric disorders performed in blood.

While clozapine has risks, relative risk of fatality is overestimated. The UK pharmacovigilance programme is efficient, but comparisons with other drugs can mislead because of reporting variations. Clozapine actually lowers mortality, partly by reducing schizophrenia-related suicides, but preventable deaths still occur. Clozapine should be used earlier and more widely, but there should be better monitoring and better management of toxicity.

BACKGROUND:Clozapine is the only recommended antipsychotic medication for individuals diagnosed with treatment-resistant schizophrenia. Unfortunately, its wider use is hindered by several possible adverse effects, some of which are rare but potentially life threatening. As such, there is a growing interest in studying clozapine use and safety in routinely collected healthcare data. However, previous attempts to characterise clozapine treatment have had low accuracy. AIM:To develop a methodology for identifying clozapine treatment dates by combining several data sources and implement this on a large clinical database. METHODS:Non-identifiable electronic health records from a large mental health provider in London and a linked database from a national clozapine blood monitoring service were used to obtain information regarding patients' clozapine treatment status, blood tests and pharmacy dispensing records. A rule-based algorithm was developed to determine the dates of starting and stopping treatment based on these data, and more than 10% of the outcomes were validated by manual review of de-identified case note text. RESULTS:A total of 3,212 possible clozapine treatment periods were identified, of which 425 (13.2%) were excluded due to insufficient data to verify clozapine administration. Of the 2,787 treatments remaining, 1,902 (68.2%) had an identified start-date. On evaluation, the algorithm identified treatments with 96.4% accuracy; start dates were 96.2% accurate within 15 days, and end dates were 85.1% accurate within 30 days. CONCLUSIONS:The algorithm produced a reliable database of clozapine treatment periods. Beyond underpinning future observational clozapine studies, we envisage it will facilitate similar implementations on additional large clinical databases worldwide.

PET and SPECT studies in treatment-resistant schizophrenia (TRS) have revealed significant alterations in regional cerebral blood flow (CBF) during clozapine treatment, which may vary according to the clinical response. Here, we used the more recent MRI approach of arterial spin labelling (ASL) to evaluate regional CBF in participants with TRS (N = 36) before starting treatment with clozapine compared to in healthy volunteers (N = 16). We then compared CBF in the TRS group, before and after 12 weeks of treatment with clozapine (N = 24); and examined the relationship of those differences against changes in Positive and Negative Syndrome Scale for Schizophrenia (PANSS) scores over the treatment period. We observed widespread reductions in CBF in TRS compared to in healthy volunteers (p < 0.05). After covarying for global CBF and age, lower CBF in frontal and parietal regions was still evident (p < 0.05, FWE corrected). Clozapine treatment was associated with longitudinal decreases in CBF in the anterior cingulate cortex (ACC) (p < 0.05). Higher striatal CBF at baseline was associated with greater improvement in total and general symptoms following clozapine, and higher hippocampal CBF was associated with greater improvement in total and positive symptoms. Longitudinal reductions in CBF in the ACC and thalamus were associated with less improvement in negative (ACC), positive (thalamus), and total (thalamus) symptoms. These findings suggest that changes in CBF on clozapine administration in TRS may accompany symptomatic improvement, and that CBF prior to clozapine initiation may determine the degree of clinical response.

AbstractPET and SPECT studies in treatment-resistant schizophrenia (TRS) have revealed significant alterations in regional cerebral blood flow (CBF) during clozapine treatment, which may vary according to the clinical response. Here, we used the more recent MRI approach of arterial spin labelling (ASL) to evaluate regional CBF in participants with TRS (N = 36) before starting treatment with clozapine compared to in healthy volunteers (N = 16). We then compared CBF in the TRS group, before and after 12 weeks of treatment with clozapine (N = 24); and examined the relationship of those differences against changes in Positive and Negative Syndrome Scale for Schizophrenia (PANSS) scores over the treatment period. We observed widespread reductions in CBF in TRS compared to in healthy volunteers (p < 0.05). After covarying for global CBF and age, lower CBF in frontal and parietal regions was still evident (p < 0.05, FWE corrected). Clozapine treatment was associated with longitudinal decreases in CBF in the anterior cingulate cortex (ACC) (p < 0.05). Higher striatal CBF at baseline was associated with greater improvement in total and general symptoms following clozapine, and higher hippocampal CBF was associated with greater improvement in total and positive symptoms. Longitudinal reductions in CBF in the ACC and thalamus were associated with less improvement in negative (ACC), positive (thalamus), and total (thalamus) symptoms. These findings suggest that changes in CBF on clozapine administration in TRS may accompany symptomatic improvement, and that CBF prior to clozapine initiation may determine the degree of clinical response.