Genetic Basis of Positive and Negative Symptom Domains in Schizophrenia

Genomic insights into the shared and distinct genetic architecture of cognitive function and schizophrenia

Cognitive impairment is a major determinant of functional outcomes in schizophrenia, however, understanding of the biological mechanisms underpinning cognitive dysfunction in the disorder remains incomplete. Here, we apply Genomic Structural Equation Modelling to identify latent cognitive factors capturing genetic liabilities to 12 cognitive traits measured in the UK Biobank. We identified three broad factors that underly the genetic correlations between the cognitive tests. We explore the overlap between latent cognitive factors, schizophrenia, and schizophrenia symptom dimensions using a complementary set of statistical approaches, applied to data from the latest schizophrenia genome-wide association study (Ncase = 53,386, Ncontrol = 77,258) and the Thematically Organised Psychosis study (Ncase = 306, Ncontrol = 1060). Global genetic correlations showed a significant moderate negative genetic correlation between each cognitive factor and schizophrenia. Local genetic correlations implicated unique genomic regions underlying the overlap between schizophrenia and each cognitive factor. We found substantial polygenic overlap between each cognitive factor and schizophrenia and biological annotation of the shared loci implicated gene-sets related to neurodevelopment and neuronal function. Lastly, we show that the common genetic determinants of the latent cognitive factors are not predictive of schizophrenia symptoms in the Norwegian Thematically Organized Psychosis cohort. Overall, these findings inform our understanding of cognitive function in schizophrenia by demonstrating important differences in the shared genetic architecture of schizophrenia and cognitive abilities.

Genomic Insights into the Shared and Distinct Genetic Architecture of Cognitive Function and Schizophrenia

Cognitive impairment is a major determinant of functional outcomes in schizophrenia, and efforts to understand the biological basis of cognitive dysfunction in the disorder are ongoing. Previous studies have suggested genetic overlap between global cognitive ability and schizophrenia, but further work is needed to delineate the shared genetic architecture. Here, we apply genomic structural equation modelling to identify latent cognitive factors capturing genetic liabilities to 12 cognitive traits measured in the UK Biobank (UKB). We explore the overlap between latent cognitive factors, schizophrenia, and schizophrenia symptom dimensions using a complementary set of statistical approaches, applied to data from the latest schizophrenia genome-wide association study (Ncase = 53,386, Ncontrol = 77,258) and the Thematically Organised Psychosis study (Ncase = 306, Ncontrol = 1060). We identified three broad factors (visuo-spatial, verbal analytic and decision/reaction time) that underly the genetic correlations between the UKB cognitive tests. Global genetic correlations showed a significant but moderate negative genetic correlation between each cognitive factor and schizophrenia. Local genetic correlations implicated unique genomic regions underlying the overlap between schizophrenia and each cognitive factor. We found evidence of substantial polygenic overlap between each cognitive factor and schizophrenia but show that most loci shared between the latent cognitive factors and schizophrenia have unique patterns of association with the cognitive factors. Biological annotation of the shared loci implicated gene-sets related to neurodevelopment and neuronal function. Lastly, we find that the common genetic determinants of the latent cognitive factors are not predictive of schizophrenia symptom dimensions. Overall, these findings inform our understanding of cognitive function in schizophrenia by demonstrating important differences in the shared genetic architecture of schizophrenia and cognitive abilities.

Dimensional characteristics of persistent negative symptoms in schizophrenia and their relationships with schizotypy in first-degree relatives

PURPOSE OF THE ARTICLE

Schizophrenia with persistent negative symptoms (PNS) may have different characteristics regarding negative symptom dimensions and heritability patterns. This study aimed to investigate the dimensional characteristics of PNS and their relationships with schizotypal features in first-degree relatives (FDRs).

MATERIALS AND METHODS

The study included 142 patients, 142 FDRs, and 71 healthy controls (HC). Patients were evaluated with the Positive and Negative Symptom Scale (PANSS), Brief Negative Symptom Scale (BNSS), Calgary Depression Scale for Schizophrenia (CDSS), and Simpson-Angus Scale (SAS). Schizotypy Personality Questionnaire was applied to FDR and HC groups. Clinical symptoms were compared between primary-PNS, secondary-PNS, and non-PNS groups. In addition, schizotypy scores were compared between FDRs and HCs. Then, the relationship between the symptoms of the patients in the PNS group and the schizotypy scores of their relatives was evaluated by multiple regression analysis.

RESULTS

All negative symptom dimension scores were similar in primary-PNS and secondary-PNS and lowest in non-PNS. PNS-FDR had higher in all schizotypy scores than non-PNS-FDR and HC, except for lack of close friends and social anxiety. In the PNS group, positive symptom severity and PANSS experiential deficit scores significantly predicted positive and negative schizotypy scores in relatives. Negative schizotypy was associated with asociality.

CONCLUSIONS

The PNS is likely a subtype in which the genetic basis of negative symptoms is stronger and is associated with genetic abnormalities shared by positive and negative schizotypy dimensions in relatives. Family-based genetic studies will be beneficial in enlightening the genetic etiology of PNS.

Dietary total antioxidant capacity and serum 8-OHdG in patients with schizophrenia

BACKGROUND

Dietary total antioxidant capacity serves as an indicator for dietary quality and reflects daily antioxidant intake. This study aimed to determine the oxidative stress status of patients with schizophrenia and to examine the relationship between dietary total antioxidant capacity (dTAC) and 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker for oxidative stress.

METHODS

This study was conducted in Turkey and involved 40 patients diagnosed with schizophrenia or schizoaffective disorder according to the Diagnostic and Statistical Manual of Mental Disorders, 5th ed., and 30 healthy controls matched for age and gender. The participants' sociodemographic characteristics and nutritional habits were determined through face-to-face interviews and through the use of questionnaires. The dTAC and dietary oxidative balance scores were calculated using a three-day dietary intake record. 8-OHdG levels were analyzed in the serum samples collected from the subjects.

RESULTS

Dietary ferric reducing antioxidant power (FRAP-1, FRAP-2), Trolox equivalence antioxidant capacity (TEAC), and oxygen radical absorbance capacity (H-ORAC) values were lower in patients with schizophrenia than in the healthy controls (P < 0.05). Serum 8-OHdG levels were found similar in both groups (P > 0.05).

CONCLUSION

Nutritional interventions are needed in patients with schizophrenia given that insufficient antioxidant intake may increase oxidative stress, which in turn affects disease development. Therefore, healthy nutrition, especially sufficient intake of dietary antioxidants, should be encouraged in patients with schizophrenia.

Six-year trajectories and associated factors of positive and negative symptoms in schizophrenia patients, siblings, and controls: Genetic Risk and Outcome of Psychosis (GROUP) study

Positive and negative symptoms are prominent but heterogeneous characteristics of schizophrenia spectrum disorder (SSD). Within the framework of the Genetic Risk and Outcome of Psychosis (GROUP) longitudinal cohort study, we aimed to distinguish and identify the genetic and non-genetics predictors of homogenous subgroups of the long-term course of positive and negative symptoms in SSD patients (n = 1119) and their unaffected siblings (n = 1059) in comparison to controls (n = 586). Data were collected at baseline, and after 3- and 6-year follow-ups. Group-based trajectory modeling was applied to identify latent subgroups using positive and negative symptoms or schizotypy scores. A multinomial random-effects logistic regression model was used to identify predictors of latent subgroups. Patients had decreasing, increasing, and relapsing symptoms course. Unaffected siblings and healthy controls had three to four subgroups characterized by stable, decreasing, or increasing schizotypy. PRSSCZ did not predict the latent subgroups. Baseline symptoms severity in patients, premorbid adjustment, depressive symptoms, and quality of life in siblings predicted long-term trajectories while were nonsignificant in controls. In conclusion, up to four homogenous latent subgroups of symptom course can be distinguished within patients, siblings, and controls, while non-genetic factors are the main factors associated with the latent subgroups.

Gene and schizophrenia in the pregenome and postgenome-wide association studies era: a bibliometric analysis and network visualization

This study aimed to perform a bibliometric analysis on genetic studies in schizophrenia in the pregenome-wide association studies (GWAS) and post-GWAS era. We searched the literature on genes and schizophrenia using the Scopus database. The documents increased with time, especially after the human genome project and International HapMap Project, with the highest citation in 2008. The top occurrence author keywords were discovered to be different in the pre-GWAS and post-GWAS eras, reflecting the progress of genetic studies connected to schizophrenia. Emerging keywords highlighted a trend towards an application of precision medicine, showing an interplay of environmental exposures as well as genetic factors in schizophrenia pathogenesis, progression, and response to therapy. In conclusion, the gene and schizophrenia literature has grown rapidly after the human genome project, and the temporal variation in the author keywords pattern reflects the trend of genetic studies related to schizophrenia in the pre-GWAS and post-GWAS era.

[Therapeutic drug monitoring of antipsychotic drugs in routine psychiatric practice]

OBJECTIVE

To evaluate the relationship between daily doses of antipsychotic drugs, their serum concentrations, and characteristics of patients treated for schizophrenia or schizophreniform disorder in day-to-day clinical practice.

MATERIAL AND METHODS

A total of 187 patients were included in the study, 77 (41.1%) patients were on monotherapy, and 110 (58.9%) patients received two or more antipsychotics. Patients age was 27.8±8.1 years, and their body weight was 79.8±15.6 kg. The sample was represented mainly by young men (93.0%). The proportion of smokers was 37.4%. The appropriate HPLC-MS/MS method was used for the simultaneous analysis of 8 antipsychotics and its active metabolites. Serum concentrations of the drugs aripiprazole (ARI), chlorpromazine (CPZ), haloperidol (HAL), zuclopenthixol (ZUC), clozapine (CLO), risperidone (RIS), quetiapine (QUE), olanzapine (OLA), norclozapine (N-desmethylclozapine, NOR), 9-hydroxyrisperidone (9-OH-RIS), dehydroaripiprazole (DGA) were measured. The serum concentration/dose ratio (C/D) was employed as the primary outcome measure, as doses were not kept constant during the study. The active antipsychotic fraction (drug+active metabolite, active moiety - AM) was also evaluated for RIS and ARI. In addition, the metabolite/parent ratio (MPR) was evaluated for RIS and ARI.

RESULTS

A total of 265 biological samples were obtained, 421 and 203 measurements of the concentration of drugs and their metabolites were carried out, respectively. Overall, 48% of antipsychotics levels were in the expected therapeutic ranges, 30% were below therapeutic ranges, and 22% were above them. A total of 55 patients underwent dose adjustments or drug changes due to ineffectiveness or side-effects. It has been found that smoking reduces the level of C/D for CLO (p<0.01, Mann-Whitney test). We have established that comedication with CLO significantly increases the C/D ratio of QUE (p<0.05, Mann-Whitney test). We have not revealed any influence of weight and age of the subjects on the C/D. The dose-concentration regression relationships are formalized for all AP.

CONCLUSION

Therapeutical drug monitoring (TDM) is an essential tool to personalize antipsychotic therapy. Careful analysis of TDM data can contribute significantly to the study of the impact of individual patient characteristics on systemic exposure to these drugs.

[Molecular-genetic and immunological aspects of the formation of psychopathological symptoms in schizophrenia]

The authors present the data indicating that the formation of psychopathological symptoms of schizophrenia is due to complex and diverse genetic factors associated with various functional and metabolic pathways at different stages of ontogenesis. Despite the fact that at present the genetic basis of positive and negative symptoms as the main pathophysiological manifestations of schizophrenia remains largely unknown, the current level of research allows the identification of some common and unique associations for positive and negative disorders. Based on the analysis of the literature, the specificity of the association of genetic variants with negative symptoms of schizophrenia is shown. It has been also suggested that genes of the immune system may be specifically associated with negative symptoms of schizophrenia. The relevance of studying the relationship of immune system genes, in particular, pro- and anti-inflammatory cytokines, with dimensional characteristics of negative symptoms (abulia-apathy and expressive deficit) is substantiated. Studies of this type have not yet been conducted, despite accumulating data indicating that the heterogeneity of negative symptoms is based on different neurobiological mechanisms. It is concluded that the immunological and molecular genetic study of the subdomains of psychopathological symptoms can be promising as part of the transition to deep phenotyping, which seems to be especially relevant for the study of such an extremely heterogeneous disease from a clinical point of view as schizophrenia. The development of this area is important for solving the problems of precision medicine, which aims to provide the most effective therapy for a particular patient by stratifying the disease into subclasses, taking into account their biological basis.

The Latent Structure of Negative Symptoms in the General Population in Adolescence and Emerging Adulthood

Negative symptoms predict adverse outcomes within psychotic disorders, in individuals at high-risk for psychosis, and in young people in the community. There is considerable interest in the dimensional structure of negative symptoms in clinical samples, and accumulating evidence suggests a 5-factor structure. Little is known about the underlying structure of negative symptoms in young people despite the importance of this developmental stage for mental health. We used confirmatory factor analysis to test the structure of parent-reported negative symptoms at mean ages 16.32 (SD 0.68, N = 4974), 17.06 (SD 0.88, N = 1469) and 22.30 (SD 0.93, N = 5179) in a community sample. Given previously reported associations between total negative symptoms and genome-wide polygenic scores (GPS) for major depressive disorder (MDD) and schizophrenia in adolescence, we assessed associations between individual subdomains and these GPSs. A 5-factor model of flat affect, alogia, avolition, anhedonia, and asociality provided the best fit at each age and was invariant over time. The results of our linear regression analyses showed associations between MDD GPS with avolition, flat affect, anhedonia, and asociality, and between schizophrenia GPS with avolition and flat affect. We showed that a 5-factor structure of negative symptoms is present from ages 16 to 22 in the community. Avolition was most consistently associated with polygenic liability to MDD and schizophrenia, and alogia was least associated. These findings highlight the value of dissecting negative symptoms into psychometrically derived subdomains and may offer insights into early manifestation of genetic risk for MDD and schizophrenia.

"Predictors of Negative Symptom Domains in Outpatients with Schizophrenia: A Cross-Sectional Study"

"Background: Current research suggests that negative symptoms may not be a unitary construct. Factor analytic studies typically found evidence for a two-factor solution of the negative symptom domain: the expressive and the volitional deficit. This study aimed to investigate whether the two-factor solution of negative symptoms is supported across different instruments of evaluation: PANSS and NSA-16 in outpatients with schizophrenia and to explore the relationship between these domains and sociodemographic, clinical, and metabolic outcomes, routinely assessed in daily practice.Another aim was to determine clinical predictors of negative symptoms domains among these variables. Materials and methods: 107 patients with schizophrenia were included in this cross-sectional study. The Principal Component Analysis was used to identify negative symptom domains and Spearman's rank correlation coefficient and multiple regression analyses were used to assess the relationship between the negative symptom domains and clinical variables. Results: PCA indicated a two-component solution explaining 85.2% of the variance for the NSA-16 subscales, reflecting an expressive deficit and an experiential deficit component. Age of onset of the disease and the cognitive deficit were significant predictors of the expressive deficit , body mass index and the number of admissions in the hospital for the experiential deficit. Conclusions: The current findings indicate that the expressive deficit and the experiential deficit should be considered as distinct domains of the psychopathology and should be rated separately"

Evidence of an interaction between FXR1 and GSK3β polymorphisms on levels of Negative Symptoms of Schizophrenia and their response to antipsychotics

BACKGROUND

Genome-Wide Association Studies (GWASs) have identified several genes associated with Schizophrenia (SCZ) and exponentially increased knowledge on the genetic basis of the disease. In addition, products of GWAS genes interact with neuronal factors coded by genes lacking association, such that this interaction may confer risk for specific phenotypes of this brain disorder. In this regard, fragile X mental retardation syndrome-related 1 (FXR1) gene has been GWAS associated with SCZ. FXR1 protein is regulated by glycogen synthase kinase-3β (GSK3β), which has been implicated in pathophysiology of SCZ and response to antipsychotics (APs). rs496250 and rs12630592, two eQTLs (Expression Quantitative Trait Loci) of FXR1 and GSK3β, respectively, interact on emotion stability and amygdala/prefrontal cortex activity during emotion processing. These two phenotypes are associated with Negative Symptoms (NSs) of SCZ suggesting that the interaction between these SNPs may also affect NS severity and responsiveness to medication.

METHODS

To test this hypothesis, in two independent samples of patients with SCZ, we investigated rs496250 by rs12630592 interaction on NS severity and response to APs. We also tested a putative link between APs administration and FXR1 expression, as already reported for GSK3β expression.

RESULTS

We found that rs496250 and rs12630592 interact on NS severity. We also found evidence suggesting interaction of these polymorphisms also on response to APs. This interaction was not present when looking at positive and general psychopathology scores. Furthermore, chronic olanzapine administration led to a reduction of FXR1 expression in mouse frontal cortex.

DISCUSSION

Our findings suggest that, like GSK3β, FXR1 is affected by APs while shedding new light on the role of the FXR1/GSK3β pathway for NSs of SCZ.

Treatment Capacity and Clinical Outcomes for Patients With Schizophrenia Who Were Treated With Electroconvulsive Therapy: A Retrospective Cohort Study

BACKGROUND

Patients with schizophrenia are often found incapable to consent to psychiatric treatment. We evaluated clinical outcomes for incapable and capable patients with schizophrenia treated with electroconvulsive therapy (ECT).

METHODS

We conducted a chart review of all inpatients treated with an acute course of ECT between 2010 and 2018 at the Centre for Addiction and Mental Health, Toronto, Canada. Short-term outcomes included treatment response and cognitive impairment. We assessed whether incapable patients regained the capacity to consent to treatment. Long-term outcomes included readmissions and subsequent courses of acute or maintenance ECT.

RESULTS

A total of 159 (67%) incapable and 79 (33%) capable patients were included. Patients experienced treatment response (incapable, n = 108, 67.9%; capable, n = 52, 65.8%; P = .771) and few experienced cognitive impairment (incapable, n = 21, 13.2%; capable, n = 19, 24.1%; P = .043). A minority of patients were treated with a subsequent course of acute ECT (incapable, n = 46, 28.9%; capable, n = 16, 20.3%; P = .162). Incapable patients were more likely to be treated with maintenance ECT for at least 6 months (incapable, n = 46, 28.9%; capable, n = 13, 16.5%; P = .039). Both groups had similar readmission rates (incapable, n = 70, 44.0%; capable, n = 35, 44.3%; P = 1.000). Eight (5.0%) incapable patients regained capacity and 7 consented to further treatment.

CONCLUSIONS

Irrespective of treatment capacity, the majority of patients demonstrated clinical improvement. Incapable patients experienced less cognitive side effects when compared with capable patients, though they had fewer treatments overall. This study informs clinicians, patients, and substitute decision-makers about the outcomes and challenges of ECT in patients with schizophrenia.

Why does age of onset predict clinical severity in schizophrenia? A multiplex extended pedigree study

Schizophrenia has substantial variation in symptom severity, course of illness, and overall functioning. Earlier age of onset (AOO) is consistently associated with negative outcomes and yet the causes of this association are still unknown. We used a multiplex, extended pedigree design (total N = 771; 636 relatives from 43 multigenerational families with at least 2 relatives diagnosed with schizophrenia and 135 matched controls) to examine among the schizophrenia relatives (N = 103) the relationship between AOO and negative and positive symptom severity, cognition, and community functioning. Most importantly, we assessed whether there are shared genetic effects between AOO and negative symptoms, positive symptoms, cognition, and community functioning. As expected, earlier AOO was significantly correlated with increased severity of negative and positive symptoms and poorer cognition and community functioning among schizophrenia patients. Notably, the genetic correlation between AOO of schizophrenia and negative symptoms was significant (R_g = -1.00, p = .007). Although the genetic correlations between AOO and positive symptoms, cognition, and community functioning were estimated at maximum and in the predicted direction, they were not statistically significant. AOO of schizophrenia itself was modestly heritable, although not significant and negative symptoms, positive symptoms, and cognition were all strongly and significantly heritable. In sum, we replicated prior findings indicating that earlier AOO is associated with increased symptom severity and extended the literature by detecting shared genetic effects between AOO and negative symptoms, suggestive of pleiotropy.

A systematic review and narrative synthesis of data-driven studies in schizophrenia symptoms and cognitive deficits

To tackle the phenotypic heterogeneity of schizophrenia, data-driven methods are often applied to identify subtypes of its symptoms and cognitive deficits. However, a systematic review on this topic is lacking. The objective of this review was to summarize the evidence obtained from longitudinal and cross-sectional data-driven studies in positive and negative symptoms and cognitive deficits in patients with schizophrenia spectrum disorders, their unaffected siblings and healthy controls or individuals from general population. Additionally, we aimed to highlight methodological gaps across studies and point out future directions to optimize the translatability of evidence from data-driven studies. A systematic review was performed through searching PsycINFO, PubMed, PsycTESTS, PsycARTICLES, SCOPUS, EMBASE and Web of Science electronic databases. Both longitudinal and cross-sectional studies published from 2008 to 2019, which reported at least two statistically derived clusters or trajectories were included. Two reviewers independently screened and extracted the data. In this review, 53 studies (19 longitudinal and 34 cross-sectional) that conducted among 17,822 patients, 8729 unaffected siblings and 5520 controls or general population were included. Most longitudinal studies found four trajectories that characterized by stability, progressive deterioration, relapsing and progressive amelioration of symptoms and cognitive function. Cross-sectional studies commonly identified three clusters with low, intermediate (mixed) and high psychotic symptoms and cognitive profiles. Moreover, identified subgroups were predicted by numerous genetic, sociodemographic and clinical factors. Our findings indicate that schizophrenia symptoms and cognitive deficits are heterogeneous, although methodological limitations across studies are observed. Identified clusters and trajectories along with their predictors may be used to base the implementation of personalized treatment and develop a risk prediction model for high-risk individuals with prodromal symptoms.

Polygenic signal for symptom dimensions and cognitive performance in patients with chronic schizophrenia

Genetic etiology of psychopathology symptoms and cognitive performance in schizophrenia is supported by candidate gene and polygenic risk score (PRS) association studies. Such associations are reported to be dependent on several factors - sample characteristics, illness phase, illness severity etc. We aimed to examine if schizophrenia PRS predicted psychopathology symptoms and cognitive performance in patients with chronic schizophrenia. We also examined if schizophrenia associated autosomal loci were associated with specific symptoms or cognitive domains. Case-only analysis using data from the Clinical Antipsychotics Trials of Intervention Effectiveness-Schizophrenia trials (n = 730). PRS was constructed using Psychiatric Genomics Consortium (PGC) leave one out genome wide association analysis as the discovery data set. For candidate region analysis, we selected 105-schizophrenia associated autosomal loci from the PGC study. We found a significant effect of PRS on positive symptoms at p-threshold (PT ) of 0.5 (R2 = 0.007, p = 0.029, empirical p = 0.029) and negative symptoms at PT of 1e-07 (R2 = 0.005, p = 0.047, empirical p = 0.048). For models that additionally controlled for neurocognition, best fit PRS predicted positive (p-threshold 0.01, R2 = 0.007, p = 0.013, empirical p = 0.167) and negative symptoms (p-threshold 0.1, R2 = 0.012, p = 0.004, empirical p = 0.329). No associations were seen for overall neurocognitive and social cognitive performance tests. Post-hoc analyses revealed that PRS predicted working memory and vigilance performance but did not survive correction. No candidate regions that survived multiple testing corrections were associated with either symptoms or cognitive performance. Our findings point to potentially distinct pathogenic mechanisms for schizophrenia symptoms.