Associations of psychotic symptom dimensions with clinical and developmental variables in twin and general clinical samples.

BACKGROUND: Positive, negative and disorganised psychotic symptom dimensions are associated with clinical and developmental variables, but differing definitions complicate interpretation. Additionally, some variables have had little investigation. AIMS: To investigate associations of psychotic symptom dimensions with clinical and developmental variables, and familial aggregation of symptom dimensions, in multiple samples employing the same definitions. METHOD: We investigated associations between lifetime symptom dimensions and clinical and developmental variables in two twin and two general psychosis samples. Dimension symptom scores and most other variables were from the Operational Criteria Checklist. We used logistic regression in generalised linear mixed models for combined sample analysis (n = 875 probands). We also investigated correlations of dimensions within monozygotic (MZ) twin pairs concordant for psychosis (n = 96 pairs). RESULTS: Higher symptom scores on all three dimensions were associated with poor premorbid social adjustment, never marrying/cohabiting and earlier age at onset, and with a chronic course, most strongly for the negative dimension. The positive dimension was also associated with Black and minority ethnicity and lifetime cannabis use; the negative dimension with male gender; and the disorganised dimension with gradual onset, lower premorbid IQ and substantial within twin-pair correlation. In secondary analysis, disorganised symptoms in MZ twin probands were associated with lower premorbid IQ in their co-twins. CONCLUSIONS: These results confirm associations that dimensions share in common and strengthen the evidence for distinct associations of co-occurring positive symptoms with ethnic minority status, negative symptoms with male gender and disorganised symptoms with substantial familial influences, which may overlap with influences on premorbid IQ.

Neuropsychological differences between treatment-resistant and treatment-responsive schizophrenia: a meta-analysis.

Antipsychotic treatment resistance affects up to a third of individuals with schizophrenia. Of those affected, 70-84% are reported to be treatment resistant from the outset. This raises the possibility that the neurobiological mechanisms of treatment resistance emerge before the onset of psychosis and have a neurodevelopmental origin. Neuropsychological investigations can offer important insights into the nature, origin and pathophysiology of treatment-resistant schizophrenia (TRS), but methodological limitations in a still emergent field of research have obscured the neuropsychological discriminability of TRS. We report on the first systematic review and meta-analysis to investigate neuropsychological differences between TRS patients and treatment-responsive controls across 17 published studies (1864 participants). Five meta-analyses were performed in relation to (1) executive function, (2) general cognitive function, (3) attention, working memory and processing speed, (4) verbal memory and learning, and (5) visual-spatial memory and learning. Small-to-moderate effect sizes emerged for all domains. Similarly to previous comparisons between unselected, drug-naïve and first-episode schizophrenia samples v. healthy controls in the literature, the largest effect size was observed in verbal memory and learning [dl = -0.53; 95% confidence interval (CI) -0.29 to -0.76; z = 4.42; p < 0.001]. A sub-analysis of language-related functions, extracted from across the primary domains, yielded a comparable effect size (dl = -0.53, 95% CI -0.82 to -0.23; z = 3.45; p < 0.001). Manipulating our sampling strategy to include or exclude samples selected for clozapine response did not affect the pattern of findings. Our findings are discussed in relation to possible aetiological contributions to TRS.

Genetic copy number variants, cognition and psychosis: a meta-analysis and a family study.

The burden of large and rare copy number genetic variants (CNVs) as well as certain specific CNVs increase the risk of developing schizophrenia. Several cognitive measures are purported schizophrenia endophenotypes and may represent an intermediate point between genetics and the illness. This paper investigates the influence of CNVs on cognition. We conducted a systematic review and meta-analysis of the literature exploring the effect of CNV burden on general intelligence. We included ten primary studies with a total of 18,847 participants and found no evidence of association. In a new psychosis family study, we investigated the effects of CNVs on specific cognitive abilities. We examined the burden of large and rare CNVs (>200 kb, <1% MAF) as well as known schizophrenia-associated CNVs in patients with psychotic disorders, their unaffected relatives and controls (N = 3428) from the Psychosis Endophenotypes International Consortium (PEIC). The carriers of specific schizophrenia-associated CNVs showed poorer performance than non-carriers in immediate (P = 0.0036) and delayed (P = 0.0115) verbal recall. We found suggestive evidence that carriers of schizophrenia-associated CNVs had poorer block design performance (P = 0.0307). We do not find any association between CNV burden and cognition. Our findings show that the known high-risk CNVs are not only associated with schizophrenia and other neurodevelopmental disorders, but are also a contributing factor to impairment in cognitive domains such as memory and perceptual reasoning, and act as intermediate biomarkers of disease risk.

The impact of neurocognition on mentalizing in euthymic bipolar disorder versus schizophrenia.

Introduction: Theory of mind (ToM) or mentalizing deficits have been found in schizophrenia (SZ) and bipolar disorder (BD), but their relationships to patients' coexistent neurocognitive deficits are still unclear. The present study aimed to explore the possible differential involvement of neurocognitive deficits in ToM impairments in SZ and euthymic BD. Methods: Fifty-three euthymic patients with BD type I, 54 clinically stable patients with SZ, and 53 healthy participants were assessed with an advanced ToM task (Faux Pas Recognition Test) which measures cognitive and affective ToM components, and a comprehensive battery of neuropsychological measures. The three groups were matched for gender, age and education. Results: Patients with BD showed significant impairment, comparable to that in SZ, only in the cognitive facet of ToM, whereas SZ patients had significantly poorer performance than both BD patients and healthy participants in overall and affective ToM. In both SZ and euthymic BD, ToM performance was related to deficits in particular cognitive functions. After controlling for coexistent neurocognitive deficits, overall and affective ToM in SZ were still impaired whereas the cognitive ToM impairment in BD and SZ did not remained statistically significant. Conclusions: Our findings suggest a different profile of ToM deficits between SZ and BD and an independence of ToM dysfunction from concurrent neurocognitive deficits in SZ but not in BD.

Neuropsychological function at first episode in treatment-resistant psychosis: findings from the ÆSOP-10 study.

BACKGROUND: Neuropsychological investigations can help untangle the aetiological and phenomenological heterogeneity of schizophrenia but have scarcely been employed in the context of treatment-resistant (TR) schizophrenia. No population-based study has examined neuropsychological function in the first-episode of TR psychosis. METHODS: We report baseline neuropsychological findings from a longitudinal, population-based study of first-episode psychosis, which followed up cases from index admission to 10 years. At the 10-year follow up patients were classified as treatment responsive or TR after reconstructing their entire case histories. Of 145 cases with neuropsychological data at baseline, 113 were classified as treatment responsive, and 32 as TR at the 10-year follow-up. RESULTS: Compared with 257 community controls, both case groups showed baseline deficits in three composite neuropsychological scores, derived from principal component analysis: verbal intelligence and fluency, visuospatial ability and executive function, and verbal memory and learning (p values⩽0.001). Compared with treatment responders, TR cases showed deficits in verbal intelligence and fluency, both in the extended psychosis sample (t = -2.32; p = 0.022) and in the schizophrenia diagnostic subgroup (t = -2.49; p = 0.017). Similar relative deficits in the TR cases emerged in sub-/sensitivity analyses excluding patients with delayed-onset treatment resistance (p values<0.01-0.001) and those born outside the UK (p values<0.05). CONCLUSIONS: Verbal intelligence and fluency are impaired in patients with TR psychosis compared with those who respond to treatment. This differential is already detectable - at a group level - at the first illness episode, supporting the conceptualisation of TR psychosis as a severe, pathogenically distinct variant, embedded in aberrant neurodevelopmental processes.

Use of schizophrenia and bipolar disorder polygenic risk scores to identify psychotic disorders.

BACKGROUND: There is increasing evidence for shared genetic susceptibility between schizophrenia and bipolar disorder. Although genetic variants only convey subtle increases in risk individually, their combination into a polygenic risk score constitutes a strong disease predictor.AimsTo investigate whether schizophrenia and bipolar disorder polygenic risk scores can distinguish people with broadly defined psychosis and their unaffected relatives from controls. METHOD: Using the latest Psychiatric Genomics Consortium data, we calculated schizophrenia and bipolar disorder polygenic risk scores for 1168 people with psychosis, 552 unaffected relatives and 1472 controls. RESULTS: Patients with broadly defined psychosis had dramatic increases in schizophrenia and bipolar polygenic risk scores, as did their relatives, albeit to a lesser degree. However, the accuracy of predictive models was modest. CONCLUSIONS: Although polygenic risk scores are not ready for clinical use, it is hoped that as they are refined they could help towards risk reduction advice and early interventions for psychosis.Declaration of interestR.M.M. has received honoraria for lectures from Janssen, Lundbeck, Lilly, Otsuka and Sunovian.

A polygenic risk score analysis of psychosis endophenotypes across brain functional, structural, and cognitive domains.

This large multi-center study investigates the relationships between genetic risk for schizophrenia and bipolar disorder, and multi-modal endophenotypes for psychosis. The sample included 4,242 individuals; 1,087 patients with psychosis, 822 unaffected first-degree relatives of patients, and 2,333 controls. Endophenotypes included the P300 event-related potential (N = 515), lateral ventricular volume (N = 798), and the cognitive measures block design (N = 3,089), digit span (N = 1,437), and the Ray Auditory Verbal Learning Task (N = 2,406). Data were collected across 11 sites in Europe and Australia; all genotyping and genetic analyses were done at the same laboratory in the United Kingdom. We calculated polygenic risk scores for schizophrenia and bipolar disorder separately, and used linear regression to test whether polygenic scores influenced the endophenotypes. Results showed that higher polygenic scores for schizophrenia were associated with poorer performance on the block design task and explained 0.2% (p = 0.009) of the variance. Associations in the same direction were found for bipolar disorder scores, but this was not statistically significant at the 1% level (p = 0.02). The schizophrenia score explained 0.4% of variance in lateral ventricular volumes, the largest across all phenotypes examined, although this was not significant (p = 0.063). None of the remaining associations reached significance after correction for multiple testing (with alpha at 1%). These results indicate that common genetic variants associated with schizophrenia predict performance in spatial visualization, providing additional evidence that this measure is an endophenotype for the disorder with shared genetic risk variants. The use of endophenotypes such as this will help to characterize the effects of common genetic variation in psychosis.

Age-Related Differences and Heritability of the Perisylvian Language Networks.

Acquisition of language skills depends on the progressive maturation of specialized brain networks that are usually lateralized in adult population. However, how genetic and environmental factors relate to the age-related differences in lateralization of these language pathways is still not known. We recruited 101 healthy right-handed subjects aged 9-40 years to investigate age-related differences in the anatomy of perisylvian language pathways and 86 adult twins (52 monozygotic and 34 dizygotic) to understand how heritability factors influence language anatomy. Diffusion tractography was used to dissect and extract indirect volume measures from the three segments of the arcuate fasciculus connecting Wernicke's to Broca's region (i.e., long segment), Broca's to Geschwind's region (i.e., anterior segment), and Wernicke's to Geschwind's region (i.e., posterior segment). We found that the long and anterior arcuate segments are lateralized before adolescence and their lateralization remains stable throughout adolescence and early adulthood. Conversely, the posterior segment shows right lateralization in childhood but becomes progressively bilateral during adolescence, driven by a reduction in volume in the right hemisphere. Analysis of the twin sample showed that genetic and shared environmental factors influence the anatomy of those segments that lateralize earlier, whereas specific environmental effects drive the variability in the volume of the posterior segment that continues to change in adolescence and adulthood. Our results suggest that the age-related differences in the lateralization of the language perisylvian pathways are related to the relative contribution of genetic and environmental effects specific to each segment. SIGNIFICANCE STATEMENT: Our study shows that, by early childhood, frontotemporal (long segment) and frontoparietal (anterior segment) connections of the arcuate fasciculus are left and right lateralized, respectively, and remain lateralized throughout adolescence and early adulthood. In contrast, temporoparietal (posterior segment) connections are right lateralized in childhood, but become progressively bilateral during adolescence. Preliminary twin analysis suggested that lateralization of the arcuate fasciculus is a heterogeneous process that depends on the interplay between genetic and environment factors specific to each segment. Tracts that exhibit higher age effects later in life (i.e., posterior segment) appear to be influenced more by specific environmental factors.

New insights into the endophenotypic status of cognition in bipolar disorder: genetic modelling study of twins and siblings.

BACKGROUND: Twin studies have lacked statistical power to apply advanced genetic modelling techniques to the search for cognitive endophenotypes for bipolar disorder. AIMS: To quantify the shared genetic variability between bipolar disorder and cognitive measures. METHOD: Structural equation modelling was performed on cognitive data collected from 331 twins/siblings of varying genetic relatedness, disease status and concordance for bipolar disorder. RESULTS: Using a parsimonious AE model, verbal episodic and spatial working memory showed statistically significant genetic correlations with bipolar disorder (rg = |0.23|-|0.27|), which lost statistical significance after covarying for affective symptoms. Using an ACE model, IQ and visual-spatial learning showed statistically significant genetic correlations with bipolar disorder (rg = |0.51|-|1.00|), which remained significant after covarying for affective symptoms. CONCLUSIONS: Verbal episodic and spatial working memory capture a modest fraction of the bipolar diathesis. IQ and visual-spatial learning may tap into genetic substrates of non-affective symptomatology in bipolar disorder.

Post graduate clinical placements: evaluating benefits and challenges with a mixed methods cross sectional design.

BACKGROUND: Systematic evaluations of clinical placements are rare, especially when offered alongside academic postgraduate courses. An evidence-based approach is important to allow pedagogically-driven provision, rather than that solely governed by opinion or market demand. Our evaluation assessed a voluntary clinical placement scheme allied to a mental health course. METHODS: Data were collected over academic years 2010/11- 2013/14, from participating students (n = 20 to 58) and clinician supervisors (n = 10-12), using a mixed-methods cross-sectional design. Quantitative evaluation captured information on uptake, dropout, resource use, attitudes and experience, using standardized (the Placement Evaluation Questionnaire; the Scale To Assess the Therapeutic Relationship - Clinical version and the University of Toronto Placement Supervisor Evaluation) and bespoke questionnaires and audit data. Qualitative evaluation comprised two focus groups (5 clinicians, 5 students), to investigate attitudes, experience, perceived benefits, disadvantages and desired future developments. Data were analysed using framework analysis to identify a priori and emergent themes. RESULTS: High uptake (around 70 placements per annum), low dropout (2-3 students per annum; 5 %) and positive focus group comments suggested placements successfully provided added value and catered sufficiently to student demand. Students' responses confirmed that placements met expectations and the perception of benefit remained after completion with 70 % (n = 14) reporting an overall positive experience, 75 % (n = 15) reporting a pleasant learning experience, 60 % (n = 12) feeling that their clinical skills were enhanced and 85 % (n = 17) believing that it would benefit other students. Placements contributed the equivalent of seven full time unskilled posts per annum to local health care services. While qualitative data revealed perceived 'mutual benefit' for both students and clinicians, this was qualified by the inherent limitations of students' time and expertise. Areas for development included fostering learning around professionalism and students' confidence on placement. CONCLUSIONS: The addition of healthcare placements to academic postgraduate taught courses can improve their attractiveness to applicants, benefit healthcare services and enhance students' perception of their learning experiences. Well-positioned and supported placement learning opportunities could become a key differentiator for academic courses, over potential competitors. However, the actual implications for student employability and achievement remain to be established.

Ten-Year Outcomes of First-Episode Psychoses in the MRC ÆSOP-10 Study.

It has long been held that schizophrenia and other psychotic disorders have a predominately poor course and outcome. We have synthesized information on mortality, clinical and social outcomes from the ÆSOP-10 multicenter study, a 10-year follow-up of a large epidemiologically characterized cohort of 557 people with first-episode psychosis. Symptomatic remission and recovery were more common than previously believed. Distinguishing between symptom and social recovery is important given the disparity between these; even when symptomatic recovery occurs social inclusion may remain elusive. Multiple factors were associated with an increased risk of mortality, but unnatural death was reduced by 90% when there was full family involvement at first contact compared with those without family involvement. These results suggest that researchers, clinicians and those affected by psychosis should countenance a much more optimistic view of symptomatic outcome than was assumed when these conditions were first described.

Mobile phone text message reminders of antipsychotic medication: is it time and who should receive them? A cross-sectional trust-wide survey of psychiatric inpatients.

BACKGROUND: Poor adherence to antipsychotic medication is a widespread problem, and the largest predictor of relapse in patients with psychosis. Electronic reminders are increasingly used to improve medication adherence for a variety of medical conditions, but have received little attention in the context of psychotic disorders. We aimed to explore the feasibility and acceptability of including short message service (SMS) medication reminders in the aftercare plan of service users discharged from inpatient care on maintenance antipsychotic medication. METHODS: We conducted a cross-sectional, trust-wide survey in the inpatient units of the Oxleas National Health Service (NHS) Foundation Trust in the UK between June 29 and August 3, 2012. Using a self-report questionnaire and the Drug Attitude Inventory, we examined inpatient attitudes towards antipsychotic drugs, past adherence to antipsychotic medication, frequency of mobile phone ownership, and interest in receiving SMS medication reminders upon discharge from the ward. Predictors of a patient's interest in receiving electronic reminders were examined using simple logistic regression models. RESULTS: Of 273 inpatients, 85 met eligibility criteria for the survey, showed decisional capacity, and agreed to participate. Of the 85 respondents, over a third (31-35%) admitted to have forgotten to take/collect their antipsychotic medication in the past, and approximately half (49%) to have intentionally skipped their antipsychotics or taken a smaller dose than prescribed. Male patients (55%), those with negative attitudes towards antipsychotics (40%), and those unsatisfied with the information they received on medication (35%) were approximately 3 to 4 times more likely to report past intentional poor adherence. The large majority of respondents (80-82%) reported having a mobile phone and knowing how to use SMS, and a smaller majority (59%) expressed an interest in receiving SMS medication reminders after discharge. No variable predicted a patient's interest in receiving electronic reminders of antipsychotics. CONCLUSIONS: Automatic SMS reminders of antipsychotic medication were acceptable to the majority of the survey respondents as an optional service offered upon discharge from inpatient care. Automatic electronic reminders deserve further investigation as a flexible, minimally invasive, cost-effective and broadly applicable tool that can potentially improve antipsychotic adherence and clinical outcomes.

Disease-associated epigenetic changes in monozygotic twins discordant for schizophrenia and bipolar disorder.

Studies of the major psychoses, schizophrenia (SZ) and bipolar disorder (BD), have traditionally focused on genetic and environmental risk factors, although more recent work has highlighted an additional role for epigenetic processes in mediating susceptibility. Since monozygotic (MZ) twins share a common DNA sequence, their study represents an ideal design for investigating the contribution of epigenetic factors to disease etiology. We performed a genome-wide analysis of DNA methylation on peripheral blood DNA samples obtained from a unique sample of MZ twin pairs discordant for major psychosis. Numerous loci demonstrated disease-associated DNA methylation differences between twins discordant for SZ and BD individually, and together as a combined major psychosis group. Pathway analysis of our top loci highlighted a significant enrichment of epigenetic changes in biological networks and pathways directly relevant to psychiatric disorder and neurodevelopment. The top psychosis-associated, differentially methylated region, significantly hypomethylated in affected twins, was located in the promoter of ST6GALNAC1 overlapping a previously reported rare genomic duplication observed in SZ. The mean DNA methylation difference at this locus was 6%, but there was considerable heterogeneity between families, with some twin pairs showing a 20% difference in methylation. We subsequently assessed this region in an independent sample of postmortem brain tissue from affected individuals and controls, finding marked hypomethylation (>25%) in a subset of psychosis patients. Overall, our data provide further evidence to support a role for DNA methylation differences in mediating phenotypic differences between MZ twins and in the etiology of both SZ and BD.

Risk variant of oligodendrocyte lineage transcription factor 2 is associated with reduced white matter integrity.

The oligodendrocyte lineage transcription factor 2 (OLIG2) regulates the genesis of oligodendrocytes, the brain cells responsible for axonal myelination. Although it has been associated with psychiatric and neurological disorders, the impact of this gene on white matter integrity has never been investigated in humans. Using diffusion tensor imaging, we examined the effect of a single nucleotide polymorphism (rs1059004) in OLIG2 previously associated with reduced gene expression, and with psychiatric disorders on fractional anisotropy in 78 healthy subjects. We found that the risk allele (A) was associated with reduced white matter integrity in the corona radiata bilaterally. This is consistent with evidence that it is a schizophrenia susceptibility gene, and suggests that it may confer increased risk through an effect on neuroanatomical connectivity.

Interaction between effects of genes coding for dopamine and glutamate transmission on striatal and parahippocampal function.

The genes for the dopamine transporter (DAT) and the D-Amino acid oxidase activator (DAOA or G72) have been independently implicated in the risk for schizophrenia and in bipolar disorder and/or their related intermediate phenotypes. DAT and G72 respectively modulate central dopamine and glutamate transmission, the two systems most robustly implicated in these disorders. Contemporary studies have demonstrated that elevated dopamine function is associated with glutamatergic dysfunction in psychotic disorders. Using functional magnetic resonance imaging we examined whether there was an interaction between the effects of genes that influence dopamine and glutamate transmission (DAT and G72) on regional brain activation during verbal fluency, which is known to be abnormal in psychosis, in 80 healthy volunteers. Significant interactions between the effects of G72 and DAT polymorphisms on activation were evident in the striatum, parahippocampal gyrus, and supramarginal/angular gyri bilaterally, the right insula, in the right pre-/postcentral and the left posterior cingulate/retrosplenial gyri (P < 0.05, FDR-corrected across the whole brain). This provides evidence that interactions between the dopamine and the glutamate system, thought to be altered in psychosis, have an impact in executive processing which can be modulated by common genetic variation.

Comparison of outcomes for patients with and without a serious mental illness presenting to hospital for chronic obstruction pulmonary disease: retrospective observational study using administrative data.

BACKGROUND: There are few data on the profile of those with serious mental illness (SMI) admitted to hospital for physical health reasons. AIMS: To compare outcomes for patients with and without an SMI admitted to hospital in England where the primary reason for admission was chronic obstructive pulmonary disease (COPD). METHOD: This was a retrospective, observational analysis of the English Hospital Episodes Statistics data-set for the period from 1 April 2018 to 31 March 2019, for patients aged 18-74 years with COPD as the dominant reason for admission. Patient with an SMI (psychosis spectrum disorder, bipolar disorder) were identified. RESULTS: Data were available for 54 578 patients, of whom 2096 (3.8%) had an SMI. Patients with an SMI were younger, more likely to be female and more likely to live in deprived areas than those without an SMI. The burden of comorbidity was similar between the two groups. After adjusting for covariates, SMI was associated with significantly greater risk of length of stay than the median (odds ratio 1.24, 95% CI 1.12-1.37, P ≤ 0.001) and with 30-day emergency readmission (odds ratio 1.51, 95% confidence interval 1.34-1.69, P ≤ 0.001) but not with in-hospital mortality. CONCLUSION: Clinicians should be aware of the potential for poorer outcomes in patients with an SMI even when the SMI is not the primary reason for admission. Collaborative working across mental and physical healthcare provision may facilitate improved outcomes for people with SMI.

Cognitive performance at first episode of psychosis and the relationship with future treatment resistance: Evidence from an international prospective cohort study.

BACKGROUND: Antipsychotic treatment resistance affects up to a third of individuals with schizophrenia, with recent research finding systematic biological differences between antipsychotic resistant and responsive patients. Our aim was to determine whether cognitive impairment at first episode significantly differs between future antipsychotic responders and resistant cases. METHODS: Analysis of data from seven international cohorts of first-episode psychosis (FEP) with cognitive data at baseline (N = 683) and follow-up data on antipsychotic treatment response: 605 treatment responsive and 78 treatment resistant cases. Cognitive measures were grouped into seven cognitive domains based on the pre-existing literature. We ran multiple imputation for missing data and used logistic regression to test for associations between cognitive performance at FEP and treatment resistant status at follow-up. RESULTS: On average patients who were future classified as treatment resistant reported poorer performance across most cognitive domains at baseline. Univariate logistic regressions showed that antipsychotic treatment resistance cases had significantly poorer IQ/general cognitive functioning at FEP (OR = 0.70, p = .003). These findings remained significant after adjusting for additional variables in multivariable analyses (OR = 0.76, p = .049). CONCLUSIONS: Although replication in larger studies is required, it appears that deficits in IQ/general cognitive functioning at first episode are associated with future treatment resistance. Cognitive variables may be able to provide further insight into neurodevelopmental factors associated with treatment resistance or act as early predictors of treatment resistance, which could allow prompt identification of refractory illness and timely interventions.

Psychosis Endophenotypes: A Gene-Set-Specific Polygenic Risk Score Analysis.

BACKGROUND AND HYPOTHESIS: Endophenotypes can help to bridge the gap between psychosis and its genetic predispositions, but their underlying mechanisms remain largely unknown. This study aims to identify biological mechanisms that are relevant to the endophenotypes for psychosis, by partitioning polygenic risk scores into specific gene sets and testing their associations with endophenotypes. STUDY DESIGN: We computed polygenic risk scores for schizophrenia and bipolar disorder restricted to brain-related gene sets retrieved from public databases and previous publications. Three hundred and seventy-eight gene-set-specific polygenic risk scores were generated for 4506 participants. Seven endophenotypes were also measured in the sample. Linear mixed-effects models were fitted to test associations between each endophenotype and each gene-set-specific polygenic risk score. STUDY RESULTS: After correction for multiple testing, we found that a reduced P300 amplitude was associated with a higher schizophrenia polygenic risk score of the forebrain regionalization gene set (mean difference per SD increase in the polygenic risk score: -1.15 µV; 95% CI: -1.70 to -0.59 µV; P = 6 × 10-5). The schizophrenia polygenic risk score of forebrain regionalization also explained more variance of the P300 amplitude (R2 = 0.032) than other polygenic risk scores, including the genome-wide polygenic risk scores. CONCLUSIONS: Our finding on reduced P300 amplitudes suggests that certain genetic variants alter early brain development thereby increasing schizophrenia risk years later. Gene-set-specific polygenic risk scores are a useful tool to elucidate biological mechanisms of psychosis and endophenotypes, offering leads for experimental validation in cellular and animal models.

Effect of D-amino acid oxidase activator (DAOA; G72) on brain function during verbal fluency.

BACKGROUND: The D-Amino acid oxidase activator (G72 or DAOA) is believed to play a key role in the regulation of central glutamatergic transmission which is seen to be altered in psychosis. It is thought to regulate D-amino acid oxidase (DAO), which metabolizes D-serine, a co-agonist of NMDA-type glutamate receptors and to be involved in dendritic arborization. Linkage, genetic association and expression studies have implicated the G72 gene in both schizophrenia and bipolar disorder. AIMS: To examine the influence of G72 variation on brain function in the healthy population. METHOD: Fifty healthy volunteers were assessed using functional magnetic resonance imaging while performing a verbal fluency task. Regional brain activation and task-dependent functional connectivity during word generation was compared between different rs746187 genotypes. RESULTS: G72 rs746187 genotype had a significant effect on activation in the left postcentral and supramarginal gyri (FWE P < 0.05), and on the task-dependent functional coupling of this region with the retrosplenial cingulate gyrus (FWE P < 0.05). CONCLUSIONS: Our results may reflect an effect of G72 on glutamatergic transmission, mediated by an influence on D-amino acid oxidase activity, on brain areas particularly relevant to the hypoglutamatergic model of psychosis.

Cognitive function and treatment response trajectories in first-episode schizophrenia: evidence from a prospective cohort study.

OBJECTIVES: This prospective cohort study tested for associations between baseline cognitive performance in individuals early within their first episode and antipsychotic treatment of psychosis. We hypothesised that poorer cognitive functioning at the initial assessment would be associated with poorer antipsychotic response following the subsequent 6 weeks. DESIGN: Prospective cohort . SETTING: National Health Service users with a first-episode schizophrenia diagnosis, recently starting antipsychotic medication, recruited from two UK sites (King's College London, UK and University of Manchester, UK). Participants attended three study visits following screening. PARTICIPANTS: Eighty-nine participants were recruited, with 46 included in the main analysis. Participants required to be within the first 2 years of illness onset, had received minimal antipsychotic treatment, have the capacity to provide consent, and be able to read and write in English. Participants were excluded if they met remission criteria or showed mild to no symptoms. PRIMARY AND SECONDARY OUTCOME MEASURES: Antipsychotic response was determined at 6 weeks using the Positive and Negative Syndrome Scale (PANSS), with cognitive performance assessed at each visit using the Brief Assessment of Cognition in Schizophrenia (BACS). The groups identified (responders and non-responders) from trajectory analyses, as well as from >20% PANSS criteria, were compared on baseline BACS performance. RESULTS: Trajectory analyses identified 84.78% of the sample as treatment responsive, and the remaining 15.22% as treatment non-responsive. Unadjusted and adjusted logistic regressions observed no significant relationship between baseline BACS on subscale and total performance (BACS t-score: OR=0.98, p=0.620, Cohen's d=0.218) and antipsychotic response at 6 weeks. CONCLUSIONS: This investigation identified two clear trajectories of treatment response in the first 6 weeks of antipsychotic treatment. Responder and non-responder groups did not significantly differ on performance on the BACS, suggesting that larger samples may be required or that an association between cognitive performance and antipsychotic response is not observable in the first 2 years of illness onset. TRIAL REGISTRATION NUMBER: REC: 17/NI/0209.