[Positive and negative symptoms in schizophrenia: a current overview]

Major neurocognitive psychosis: a novel schizophrenia endophenotype class that is based on machine learning and resembles Kraepelin's and Bleuler's conceptions

The purpose of this study is to describe how to use the precision nomothetic psychiatry approach to (a) delineate the associations between schizophrenia symptom domains, including negative symptoms, psychosis, hostility, excitation, mannerism, formal thought disorders, psychomotor retardation (PHEMFP), and cognitive dysfunctions and neuroimmunotoxic and neuro-oxidative pathways and (b) create a new endophenotype class based on these features. We show that all symptom domains (negative and PHEMFP) may be used to derive a single latent trait called overall severity of schizophrenia (OSOS). In addition, neurocognitive test results may be used to extract a general cognitive decline (G-CoDe) index, based on executive function, attention, semantic and episodic memory, and delayed recall scores. According to partial least squares analysis, the impacts of adverse outcome pathways (AOPs) on OSOS are partially mediated by increasing G-CoDe severity. The AOPs include neurotoxic cytokines and chemokines, oxidative damage to proteins and lipids, IgA responses to neurotoxic tryptophan catabolites, breakdown of the vascular and paracellular pathways with translocation of Gram-negative bacteria, and insufficient protection through lowered antioxidant levels and impairments in the innate immune system. Unsupervised machine learning identified a new schizophrenia endophenotype class, named major neurocognitive psychosis (MNP), which is characterised by increased negative symptoms and PHEMFP, G-CoDe and the above-mentioned AOPs. Based on these pathways and phenome features, MNP is a distinct endophenotype class which is qualitatively different from simple psychosis (SP). It is impossible to draw any valid conclusions from research on schizophrenia that ignores the MNP and SP distinctions.

Schizophrenia phenomenology revisited: positive and negative symptoms are strongly related reflective manifestations of an underlying single trait indicating overall severity of schizophrenia

BACKGROUND

To examine whether negative symptoms, psychosis, hostility, excitation, and mannerism (PHEM symptoms), formal thought disorders (FTD) and psychomotor retardation (PMR) are interrelated phenomena in major neurocognitive psychosis (MNP) or deficit schizophrenia and whether those domains belong to an underlying latent vector reflecting general psychopathology.

METHODS

In this study, we recruited 120 patients with MNP or deficit schizophrenia and 54 healthy subjects and measured the above-mentioned symptom domains.

RESULTS

In MNP, there were significant associations between negative and PHEM symptoms, FTD and PMR. A single latent trait, which is essentially unidimensional, underlies these key domains of schizophrenia and MNP and additionally shows excellent internal consistency reliability, convergent validity, and predictive relevance. Confirmatory Tedrad Analysis indicates that this latent vector fits a reflective model. The lack of discriminant validity shows that positive (and PHEM or psychotic) and negative symptoms greatly overlap and probably measure the same latent construct. Soft independent modeling of class analogy (SIMCA) shows that MNP (diagnosis based on negative symptoms) is better modeled using PHEM symptoms, FTD, and PMR than negative symptoms.

CONCLUSIONS

In stable phase MNP, which is a restricted sample of the schizophrenia population, negative and PHEM symptoms, FTD and PMR belong to one underlying latent vector reflecting overall severity of schizophrenia (OSOS). The bi-dimensional concept of "positive" and "negative" symptoms cannot be validated and, therefore, future research in stable phase schizophrenia should consider that the latent phenomenon OSOS as well as its reflective manifestations are the key factors of schizophrenia phenomenology.

Pro-inflammatory cytokines and their epistatic interactions in genetic susceptibility to schizophrenia

Background

In schizophrenia, genetic background may provide a substrate for intrinsic maldevelopment of the brain through environmental influences, by recruiting neurotrophic factors and cytokines, to trigger the changes that lead to impaired neuronal functions. Cytokines being the key regulators of immune/inflammatory reactions are also known to influence the dopaminergic, noradrenergic, and serotonergic neurotransmission. Therefore, functional polymorphisms in cytokine genes may result in imbalances in the pro- and anti-inflammatory cytokine production.

Methods

We screened polymorphisms in pro- and anti-inflammatory cytokine genes using a case-control association study in a South Indian population. The role of allele, genotype, haplotype, and diplotypes of these cytokine genes and their epistatic interactions were assessed in contributing to the risk of developing schizophrenia. Meta-analysis for the reported associations was also monitored for global significance.

Results

The pro-inflammatory cytokine gene polymorphisms in IL1Ars1800587, IL6rs1800796, TNFArs361525, and IFNGrs2069718 were associated with schizophrenia. The study also provides significant evidence for strong epistatic interactions among pro-inflammatory cytokine genes IL6 and IFNG in the development of schizophrenia. In silico analysis suggested that associated risk variants were indicative of altered transcriptional activity with higher production of IL1α, IL-6, TNF-α, and IFN-ɤ cytokines. Meta-analysis indicated heterogeneity among study population while IL1Ars1800587 was found to be globally significant.

Conclusions

It is important to identify the nature of inflammatory response that can be amplified by the environment, to influence either Th1 response or Th2 response. The associated functional variants in the study are involved with increased expression resulting in higher production of the pro-inflammatory cytokines IL-1α, IL-6, TNF-α, and IFN-γ. The interaction of immunological stressors with these high producer alleles of pro-inflammatory cytokines may suggest that even a lower threshold may be sufficient to induce a resultant chronic effect on the psycho-social and environmental stressors that may result in the development and pathogenesis of schizophrenia. Understanding environmental factors that influence the expression of these pro-inflammatory cytokine genes or their interaction can possibly help in dissecting the phenotypic variation and therapeutic response to antipsychotics in schizophrenia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0569-8) contains supplementary material, which is available to authorized users.

Cognitive function and competitive employment in schizophrenia: relative contribution of insight and psychopathology

PURPOSE

This study investigated the relationships among insight, psychopathology, cognitive function, and competitive employment in order to determine whether insight and/or psychopathology carried the influence of cognitive function to competitive employment.

METHODS

We recruited 253 outpatients with stable schizophrenia and we further divided our sample into two groups of patients (unemployed and competitive employment subjects). Clinical and neuropsychological assessments were performed. All clinical variables significantly different between the two groups of subjects were subsequently analyzed using a binary logistic regression to assess their independent contribution to competitive employment in the two patients' groups. On the basis of the regression results two mediation analyses were performed.

RESULTS

Verbal memory, general psychopathology, and awareness of mental illness were significantly associated with competitive employment in our sample. Both awareness of mental illness and general psychopathology had a role in mediating the verbal memory-competitive employment relationship.

CONCLUSIONS

Taken together, these findings confirmed the importance of cognitive function in obtaining competitive employment. Our results also highlighted the independent role of general psychopathology and awareness of illness on occupational functioning in schizophrenia. Thus, a greater attention must be given to the systematic investigation of insight and general psychopathology in light of an amelioration of vocational functioning in stable schizophrenia.

Acoustic and temporal analysis of speech: A potential biomarker for schizophrenia

Currently, there are no established objective biomarkers for the diagnosis or monitoring of schizophrenia. It has been previously reported that there are notable qualitative differences in the speech of schizophrenics. The objective of this study was to determine whether a quantitative acoustic and temporal analysis of speech may be a potential biomarker for schizophrenia. In this study, 39 schizophrenic patients and 18 controls were digitally recorded reading aloud an emotionally neutral text passage from a children's story. Temporal, energy and vocal pitch features were automatically extracted from the recordings. A classifier based on linear discriminant analysis was employed to differentiate between controls and schizophrenic subjects. Processing the recordings with the algorithm developed demonstrated that it is possible to differentiate schizophrenic patients and controls with a classification accuracy of 79.4% (specificity=83.6%, sensitivity=75.2%) based on speech pause related parameters extracted from recordings carried out in standard office (non-studio) environments. Acoustic and temporal analysis of speech may represent a potential tool for the objective analysis in schizophrenia.

Disorganization and reality distortion in schizophrenia: a meta-analysis of the relationship between positive symptoms and neurocognitive deficits

BACKGROUND

Factor analytic studies have shown that in schizophrenia patients, disorganization (e.g., conceptual disorganization and bizarre behavior) is a separate dimension from other types of positive symptoms such as reality distortion (delusions and hallucinations). Although some studies have found that disorganization is more strongly linked to neurocognitive deficits and poor functional outcomes than reality distortion, the findings are not always consistent.

METHODS

A meta-analysis of 104 studies (combined n=8015) was conducted to determine the magnitude of the relationship between neurocognition and disorganization as compared to reality distortion. Additional analyses were conducted to determine whether the strength of these relationships differed depending on the neurocognitive domain under investigation.

RESULTS

The relationship between reality distortion and neurocognition was weak (r=-.04; p=.03) as compared to the moderate association between disorganization and neurocognition (r=-.23; p<.01). In each of the six neurocognitive domains that were examined, disorganization was more strongly related to neurocognition (r's range from -.20 to -.26) than to reality distortion (r's range from .01 to -.12).

CONCLUSIONS

The effect size of the relationship between neurocognition and disorganization was significantly larger than the effect size of the relationship between neurocognition and reality distortion. These results hold across several neurocognitive domains. These findings support a dimensional view of positive symptoms distinguishing disorganization from reality distortion.

Symptoms as mediators of the relationship between neurocognition and functional outcome in schizophrenia: a meta-analysis

BACKGROUND

Neurocognitive functioning in schizophrenia has received considerable attention because of its robust prediction of functional outcome. Psychiatric symptoms, in particular negative symptoms, have also been shown to predict functional outcome, but have garnered much less attention. The high degree of intercorrelation among all of these variables leaves unclear whether neurocognition has a direct effect on functional outcome or whether that relationship to functional outcome is partially mediated by symptoms.

METHODS

A meta-analysis of 73 published English language studies (total n=6519) was conducted to determine the magnitude of the relationship between neurocognition and symptoms, and between symptoms and functional outcome. A model was tested in which symptoms mediate the relationship between neurocognition and functional outcome. Functional outcome involved measures of social relationships, school and work functioning, and laboratory assessments of social skill.

RESULTS

Although negative symptoms were found to be significantly related to neurocognitive functioning (p<.01) positive symptoms were not (p=.97). The relationship was moderate for negative symptoms (r=-.24, n=4757, 53 studies), but positive symptoms were not at all related to neurocogniton (r=.00, n=1297, 25 studies). Negative symptoms were significantly correlated with functional outcome (r=-.42, p<.01), and again the correlation was higher than for positive symptoms (r=-.03, p=.55). Furthermore, our findings support a model in which negative symptoms significantly mediate the relationship between neurocognition and functional outcome (Sobel test p<.01).

CONCLUSIONS

Although neurocognition and negative symptoms are both predictors of functional outcome, negative symptoms might at least partially mediate the relationship between neurocognition and outcome.

[Perturbed consciousness in schizophrenia: an evaluation of C.D. Frith's model]

INTRODUCTION

While many neurocognitive models of schizophrenia coexist, a lot of attention has been centered on C.D. Frith's model over the past few years, especially in regard to its parsimony.

BACKGROUND

The aim of this paper is to examine its validity. The model relies on the assumption that there are two main components: self-monitoring and monitoring. The first permits one to keep consciousness of personal goals and intentions with metarepresentations. Losing consciousness of personal goals would be the source of schizophrenics' avolition and losing consciousness of personal intentions would generate reference ideas. The second component refers to the so-called "theory of mind", which is the monitoring of others' mental content (knowledge and intentions). Disturbing monitoring would cause schizophrenics persecution disillusions, third order persecutions or speech content disorders.

LITERATURE FINDINGS

After reviewing the empirical and theoretical bases of Frith's model, strengths and weaknesses are highlighted, in particular by contrasting Hardy-Baylé's and Abu-Akel's theoretical proposals. For explaining the monitoring impairments of schizophrenics, Hardy-Baylé's model emphasizes the executive functioning defect, while Abu-Akel's model proposes a "hyper theory of mind" where too many hypotheses would lead to misattributions. In addition, several criticisms of Frith's model are examined, particularly those voiced by phenomenologists who underline its reductionism presupposition and argue that the underlying cognitive conception of the "theory of mind" neglects the fundamental intersubjectivity issue. In addition, Gallagher points out that monitoring is a tautological concept and that intention is not like thinking inherent to behaviour.

CONCLUSION

Frith's model validity is finally discussed at large in the light of these criticisms and competing models, and it is concluded that the self-monitoring part of the model needs to be redefined and that the measurement of the "theory of mind" has to be standardized.

Patient characteristics and the likelihood of initiation on olanzapine or risperidone among patients with schizophrenia

Although pharmacologic treatments are available for patients with schizophrenia, little is known about how prescription patterns of atypical antipsychotic agents are related to patient characteristics. In this study, we examined the association between patient characteristics and the likelihood of being initiated on olanzapine or risperidone, two of the most frequently prescribed atypical agents for schizophrenia. We selected patients who were diagnosed with schizophrenia or schizoaffective disorder based on > or = 1 inpatient or > or = 2 outpatient ICD-9-CM codes (> or = 7 days apart) between 7/1/98 and 6/30/99 from the Veterans Health Administration (VA). We classified patients into one of three types of initiation: (a) not on olanzapine or risperidone, (b) not on any atypical agents, or (c) not on any antipsychotic agents for 6 months, and then subsequently being prescribed the target drugs. Using logistic regression, we examined whether the odds ratio of being initiated on olanzapine versus risperidone are related to patient sociodemographic and clinical characteristics. Compared to risperidone initiators, olanzapine initiators used more drugs for psychiatric conditions (including antiparkinsonian agents, typical antipsychotics, and mood stabilizers) than risperidone initiators. On the other hand, risperidone initiators had more medical comorbidities and more non-psychiatric hospitalizations. Olanzapine and risperidone appear to be prescribed to patients with different characteristics. Initiation of risperidone was more common among patients who presented with more medical comorbid conditions, whereas initiation of olanzapine was more common among patient who presented with more mental comorbid conditions. Future research needs to determine the reasons for those differences.

Initiation of atypical antipsychotic agents and health outcomes in patients with schizophrenia

BACKGROUND

Although pharmacological treatments are available for patients with schizophrenia, there is a lack of systematic and comprehensive evaluation of health outcomes following the initiation of atypical antipsychotic agents.

OBJECTIVE

To assess the effects of the initiation of olanzapine or risperidone, the two most widely prescribed atypical antipsychotics, on patients' health outcomes, as measured by changes in patient clinical characteristics between 6 months prior to and post-initiation.

METHOD

We identified patients with schizophrenia by >1 inpatient or > or = 2 outpatient ICD-9-CM codes (> or = 7 days apart) between 1 July 1998 and 30 June 1999, and those who were initiated on olanzepine or risperidone during the period 1 April 1999 to 31 March 2000 inclusive. We then subdivided these patients into three groups: (i) those who were not on olanzapine or risperidone, (ii) those who were not on any atypical agents, and (iii) those who were not on any antipsychotic agents, for 6 months prior to being issued with the new prescription. Using test of means or chi-square tests, we examined whether the initiation of olanzapine or risperidone is related to different changes in patient clinical indicators, such as number of drugs for psychiatric conditions, use of psychiatric services, and use of non-psychiatric services.

RESULTS

Between pre- and post-initiation, olanzapine initiators had a greater decrease in the number of psychiatric hospitalizations and use of psychotropic agents, whereas risperidone initiators had a greater reduction in the number of non-psychiatric hospitalizations. The initiation of olanzapine and risperidone appear to be associated with different patient health outcomes. Compared with olanzapine initiators, risperidone initiators had a greater increase in the use of treatments related to mental health, but had greater decrease in the use of treatments related to physical health.

CONCLUSION

Despite olanzapine and risperidone being often perceived as similar antipsychotic agents, our results suggest that the clinical outcomes associated with their use are different. Outcome data from routine clinical practice are required to provide a more comprehensive assessment of these drugs.

Neuropsychological performance of psychotic patients in community care: results from the UK700 study

OBJECTIVE

To compare cognitive performance in chronic schizophrenic and affective psychotic patients maintained in community care.

METHOD

We studied a sample of community-based patients (n = 707) with chronic psychotic disorders. Neuropsychological assessment was completed using the National Adult Reading Test (NART) and the Trail Making Test (TMT).

RESULTS

Affective psychotic patients had higher premorbid IQ than schizophrenic patients before adjustment for confounding factors (P=0.03); however, after adjustment for ethnic group and social class this became non-significant (P=0.19). There were no significant differences between groups on the TMT, parts A or B.

CONCLUSION

Unlike studies suggesting that schizophrenic patients are more cognitively impaired than affective psychotic patients, our study suggests a degree of cognitive homogeneity between those patients who develop a chronic illness. Measures of premorbid IQ suggest that this cognitive homogeneity exists prior to the onset of illness.