The diagnosis and understanding of schizophrenia. Part III. Speculations on the processes that underlie schizophrenic symptoms and signs

Revisiting the relationship between impaired social functioning and psychopathology in schizophrenia

Impaired social functioning is a common and well-known feature of schizophrenia. The relationship between psychopathology and social functioning is poorly understood, but substance use disorder is often suspected to negatively impact social functioning. In this empirical study, we explored the relationship between psychopathology and social functioning in two groups of patients with schizophrenia spectrum disorders with impaired social functioning: homeless and domiciled patients. The patients were thoroughly examined for psychopathology, social functioning, and substance use disorder. The results showed that all domains of psychopathology correlated significantly and negatively with social functioning. The homeless group was worse off than the domiciled group on social functioning scales, but this difference was not reflected in differences in psychopathology or substance use disorder among the two groups. Moreover, the homeless group had more disturbed and aggressive behavior, less contact with relatives, and experienced more childhood trauma and imprisonment compared with the domiciled patients. Our findings seemingly challenge the prevailing explanatory models of impaired social functioning in schizophrenia as being a result of negative symptoms or substance use disorder. Finally, the intertwinement of psychopathology and social functioning in assessment measures should be considered before concluding how specific psychopathological domains affect social functioning in schizophrenia.

COSMIN review of the PANSS Marder factor solution and other factor models in people with schizophrenia

The Positive and Negative Syndrome Scale (PANSS) is widely used to assess schizophrenia symptoms. Initially designed with three subscales, Marder et al.´s 5-factor-Model (M5M) first proposed in 1997 has been frequently used in treatment trials, but it has never been systematically reviewed for its measurement properties. We utilized the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) guideline for systematic reviews and meta-analytical procedures to assess the psychometric properties of the M5M-PANSS. COSMIN comprises several steps: literature search, risk-of-bias assessments, assessing the updated criteria for good measurement properties, feasibility aspects and grading the quality of the evidence. We further assessed the goodness of fit of other PANSS factor models. We included 95 publications. The M5M-PANSS showed good construct validity, but "insufficient" structural validity. Evidence of other COSMIN domains is largely lacking. Among the multiple (73) factor solutions examined with confirmatory methods, several other 5-factor solutions had better model fit. According to COSMIN rules the M5M should not be recommended for use. Other five-factor models such as the one proposed by Wallwork et al.1 warrant further evaluation. Nevertheless, the factor composition of the M5M and these other models was relatively similar, so previously published results should not be disregarded.

Randomized Double Blind Inpatient Study of a Gluten-Free Diet in Persons with Schizophrenia

Background

Schizophrenia and related disorders (SRD) are characterized by positive and negative symptoms, such as anhedonia and avolition. There are no current FDA approved treatments for negative symptoms, which is a critical gap in our treatment of people with SRDs, since they are a major determinant of functional impairment. An emerging literature suggests that SRDs have a relationship with immune function and inflammation. Recently an SRD subgroup with high inflammation and elevated levels of anti-gliadin antibodies (AGA) of immunoglobulin G type (IgG) has been characterized. Negative symptom improvement has been previously observed with gluten removal in this subgroup in two small clinical trials.

Methods

We conducted a 5-week confirmatory double-blind placebo-controlled trial of a gluten free diet (GFD) versus gluten-containing diet (GCD) for negative symptoms in people with SRD who have elevated AGA IgG (NCT03183609). Participants were between the ages of 18-64 years, had baseline negative symptoms and a diagnosis of schizophrenia or schizoaffective disorder. Those included were screened for an AGA IgG >20 U, no serologic evidence of celiac disease, and stable antipsychotic treatment and dose. All participants were inpatients, received a GFD and were randomized to 30 grams of gluten or rice flour daily delivered in protein shakes. The Clinical Assessment Interview for Negative Symptoms (CAINS) Motivation and Pleasure (MAP) scale was the primary outcome measure. We also examined the CAINS Expressivity (EXP) scale, the Scale for the Assessment of Negative Symptoms (SANS), the Brief Psychiatric Rating Scale (BPRS), the MATRICS Consensus Cognitive Battery (MCCB) and conducted regular side effect screening and laboratory measures for safety.

Findings

Between 2018 and 2024, we included 39 participants (N=21 GFD and N=18 GCD). There was a significant improvement over time in the CAINS MAP (treatment X time df=30.1, F=2.78, p=0.045) in the GFD compared to GCD, but no significant change in the CAINS EXP, the SANS, BPRS or MCCB. The diet was well tolerated; the most frequently occurring side effects were constipation (38.1% GFD, 33.3% GCD), sedation (33.3% GFD, 50% GCD), dry mouth (33.3% GFD, 33.3% GCD), headache (33.3% GFD, 27.8% GCD), and insomnia (33.3% GFD, 27.8% GCD).

Interpretation

This is the first large scale double-blind randomized clinical trial in SRD with AGA IgG+. This replication of smaller studies suggests that negative symptoms, particularly anhedonia and avolition may be improved. However, we did not replicate our previous finding of cognitive improvement and COVID-19 likely impacted the extent of improvement in negative symptoms due to quarantines and lockdowns. More work is needed to determine the mechanism of action of gluten removal in this subgroup with hopes of developing new treatment targets for motivational deficits of this illness.

Funding

This project was funded by NIMH R01 R01MH113617 (DL Kelly PI).

Factors predicting employment status among persons with schizophrenia: A cross-sectional study from Chennai, India

BACKGROUND

Even among other mental disorders, a diagnosis of schizophrenia is associated with an abnormally low employment rate. However, those who can find employment report mental health improvements and diminishing symptoms.

AIMS

In this cross-sectional study, we analyzed a variety of sociodemographic factors between groups of schizophrenia-diagnosed employed and unemployed individuals to attempt to determine any causal relationships.

METHODS

A group of 52 employed and 48 unemployed individuals from the same outpatient hospital were surveyed. Patients were asked about their sociodemographic background and employment history, as well as subjected to a variety of tests to quantify critical aspects of their symptomatology. These included the Positive and Negative Syndrome Scale (PANSS), Social and Occupational Functioning Assessment Scale (SOFAS), and Personal and Social Performance Scale (PSP). The Calgary Depression Scale for Schizophrenia (CDSS) and Hamilton Anxiety Rating Scale (HAM-A) were administered to assess comorbid depression and anxiety. Lastly, the Simpson Angus Scale (SAS) measured any extrapyramidal side effects caused by the patients' medications.

RESULTS

Initial analysis by the Student's t-test and chi-square test revealed correlations between employment status and symptomatology, but upon performing logistic regression, peer support was found to be the only significant predictor of employment status (OR = 0.119, CI [0.40, 0.354], p = .001). Based on these results, the creation of peer support systems at work through fostering inclusive, well-informed, and destigmatized environments should be employers' predominant focus.

CONCLUSION

Future studies conducted longitudinally can strengthen the conclusions found and confirm the optimal manners in which to address the matter of aiding the integration of schizophrenic and similarly symptomatic individuals into the labor force.

Longitudinal assessment of ventricular volume trajectories in early-stage schizophrenia: evidence of both enlargement and shrinkage

BACKGROUND

Lateral ventricular enlargement represents a canonical morphometric finding in chronic patients with schizophrenia; however, longitudinal studies elucidating complex dynamic trajectories of ventricular volume change during critical early disease stages are sparse.

METHODS

We measured lateral ventricular volumes in 113 first-episode schizophrenia patients (FES) at baseline visit (11.7 months after illness onset, SD = 12.3) and 128 age- and sex-matched healthy controls (HC) using 3T MRI. MRI was then repeated in both FES and HC one year later.

RESULTS

Compared to controls, ventricular enlargement was identified in 18.6% of patients with FES (14.1% annual ventricular volume (VV) increase; 95%CI: 5.4; 33.1). The ventricular expansion correlated with the severity of PANSS-negative symptoms at one-year follow-up (p = 0.0078). Nevertheless, 16.8% of FES showed an opposite pattern of statistically significant ventricular shrinkage during ≈ one-year follow-up (-9.5% annual VV decrease; 95%CI: -23.7; -2.4). There were no differences in sex, illness duration, age of onset, duration of untreated psychosis, body mass index, the incidence of Schneiderian symptoms, or cumulative antipsychotic dose among the patient groups exhibiting ventricular enlargement, shrinkage, or no change in VV.

CONCLUSION

Both enlargement and ventricular shrinkage are equally present in the early stages of schizophrenia. The newly discovered early reduction of VV in a subgroup of patients emphasizes the need for further research to understand its mechanisms.

The schizophrenia syndrome, circa 2024: What we know and how that informs its nature

With new data about different aspects of schizophrenia being continually generated, it becomes necessary to periodically revisit exactly what we know. Along with a need to review what we currently know about schizophrenia, there is an equal imperative to evaluate the construct itself. With these objectives, we undertook an iterative, multi-phase process involving fifty international experts in the field, with each step building on learnings from the prior one. This review assembles currently established findings about schizophrenia (construct, etiology, pathophysiology, clinical expression, treatment) and posits what they reveal about its nature. Schizophrenia is a heritable, complex, multi-dimensional syndrome with varying degrees of psychotic, negative, cognitive, mood, and motor manifestations. The illness exhibits a remitting and relapsing course, with varying degrees of recovery among affected individuals with most experiencing significant social and functional impairment. Genetic risk factors likely include thousands of common genetic variants that each have a small impact on an individual's risk and a plethora of rare gene variants that have a larger individual impact on risk. Their biological effects are concentrated in the brain and many of the same variants also increase the risk of other psychiatric disorders such as bipolar disorder, autism, and other neurodevelopmental conditions. Environmental risk factors include but are not limited to urban residence in childhood, migration, older paternal age at birth, cannabis use, childhood trauma, antenatal maternal infection, and perinatal hypoxia. Structural, functional, and neurochemical brain alterations implicate multiple regions and functional circuits. Dopamine D-2 receptor antagonists and partial agonists improve psychotic symptoms and reduce risk of relapse. Certain psychological and psychosocial interventions are beneficial. Early intervention can reduce treatment delay and improve outcomes. Schizophrenia is increasingly considered to be a heterogeneous syndrome and not a singular disease entity. There is no necessary or sufficient etiology, pathology, set of clinical features, or treatment that fully circumscribes this syndrome. A single, common pathophysiological pathway appears unlikely. The boundaries of schizophrenia remain fuzzy, suggesting the absence of a categorical fit and need to reconceptualize it as a broader, multi-dimensional and/or spectrum construct.

[The new psychopathological paradigm of schizophrenia and schizophrenia spectrum disorders]

The basis of the new paradigm, as an attempt to modernize the systematics of psychopathological disorders, is the concept of simultaneous representation of two relatively independent domains (founded by neurobiological processes) in the clinical space of schizophrenia - negative and positive disorders. The study established the spectra of functional activity of endogenous dimensions, as well as the trajectories of their development, which determine the dominance of predominantly negative or positive symptoms (negative/positive schizophrenia) during the course of the disease. The differentiated impact of endogenous domains on constitutional characterological structures accompanied by the formation of pseudopsychiopathies and subpsychotic personality disorders is observed.

What Kurt Schneider Really Said and What the DSM Has Made of it in Its Different Editions: A Plea to Redefine Hallucinations in Schizophrenia

Kurt Schneider has played a leading role in shaping our current view of schizophrenia, placing certain manifestations of delusions and hallucinations at the center of the disorder, especially ideas of persecution and voice-hearing. The first part of this review summarizes Schneider's original ideas and then traces how the different editions of the DSM merged aspects of Kraepelin's, Bleuler's, and Schneider's historical concepts. Special attention is given to the transition from the DSM-IV to the DSM-5, which eliminated much of Schneider's original concept. In the second part of the article, we contrast the current definition of hallucination in the DSM-5 with that of Schneider. We present empirically derived arguments that favor a redefinition of hallucinations, much in accordance with Schneider's original ideas. We plea for a two-dimensional model of hallucinations that represents the degree of insight and perceptuality, ranging from thoughts with full "mineness" via perception-laden thoughts and intrusions (including "as if" experiences") to hallucinations. While we concur with the DSM-5 that cognitions that are indistinguishable from perceptions should be labeled as hallucinations, we suggest expanding the definition to internally generated sensory phenomena, including those with only partial resemblance to external perceptions, that the individual considers real and that may lie at the heart of a subsequent delusional superstructure.

A conversation analytic approach to schizophrenic interaction: methodological reflections on disruptions of the common-sense world

Certain schools of phenomenological psychiatry conceive of schizophrenia as a pathology of common-sense. Ethnomethodological enquiry, with its roots in Schutzian social phenomenology, takes as its domain, topic, and substance of study the ongoing achievement of a common-sense world between social members. Yet, dialogue between psychiatry and ethnomethodological approaches is thin. In this article, we discuss a conversation analytic approach to schizophrenic interaction which has generated and utilized a model of a five-world manifold to frame analyses of talk-in-interaction. 'Worlds' are conceived, after Schutz, as finite domains of meaning, and the model operates as a breach of natural attitude assumptions to examine mechanisms of the constitution of the one-world-in-common of common-sense. It is suggested that certain aspects of schizophrenic talk might receive account in terms of a loss of integration between these five domains of meaning. Conversation Analytic methods were applied to transcripts of audio recordings of psychiatric interviews but encountered hurdles that motivated the broadening of methodological scope. Such hurdles included a weakening of the next turn proof procedure, implicit reification of the schizophrenia construct, and problems of translation presented by the analyst's normative membership encountering non-normative life-worlds of schizophrenic experience. Strategic responses to these hurdles included exploring linkages between phenomenological psychiatry and ethnomethodological approaches, as well as an engagement of ethnomethodological self-reflection and conceptual clarification of the schizophrenia construct in line with Garfinkel's unique adequacy requirement. The manifold model is glossed, and interaction between two of its worlds - a world of concrete, situational immediacies and another of abstract organizations - is explored in more detail via analysis of conversational data. It is suggested that the five-world model, along with further micro-analysis of talk-in-interaction, might have implications in psychiatry for topics such as autism, double bookkeeping, concretism, theories of disturbed indexicality, and insight attribution. We conclude that the consideration of atypical interaction obliges the interaction analyst to take account of their own implicit normative world-frames and that the use of domain-specific top-down models in conjunction with the inductive approach of Conversation Analysis may extend the reach of CA to facilitate productive dialogue with other disciplines.

Efficacy of Serotonin and Dopamine Activity Modulators in the Treatment of Negative Symptoms in Schizophrenia: A Rapid Review

Schizophrenia is among the fifteen most disabling diseases worldwide. Negative symptoms (NS) are highly prevalent in schizophrenia, negatively affect the functional outcome of the disorder, and their treatment is difficult and rarely specifically investigated. Serotonin-dopamine activity modulators (SDAMs), of which aripiprazole, cariprazine, brexpiprazole, and lumateperone were approved for schizophrenia treatment, represent a possible therapy to reduce NS. The aim of this rapid review is to summarize the evidence on this topic to make it readily available for psychiatrists treating NS and for further research. We searched the PubMed database for original studies using SDAM, aripiprazole, cariprazine, brexpiprazole, lumateperone, schizophrenia, and NS as keywords. We included four mega-analyses, eight meta-analyses, two post hoc analyses, and 20 clinical trials. Aripiprazole, cariprazine, and brexpiprazole were more effective than placebo in reducing NS. Only six studies compared SDAMs with other classes of antipsychotics, demonstrating a superiority in the treatment of NS mainly for cariprazine. The lack of specific research and various methodological issues, related to the study population and the assessment of NS, may have led to these partial results. Here, we highlight the need to conduct new methodologically robust investigations with head-to-head treatment comparisons and long-term observational studies on homogeneous groups of patients evaluating persistent NS with first- and second-generation scales, namely the Brief Negative Symptom Scale and the Clinical Assessment Interview for Negative Symptoms. This rapid review can expand research on NS therapeutic strategies in schizophrenia, which is fundamental for the long-term improvement of patients’ quality of life.

Latent Inhibition in Schizophrenia and Schizotypy

Background

The Salience Hypothesis posits that aberrations in the assignment of salience culminate in hallucinations and unusual beliefs, the "positive symptoms" of schizophrenia. Evidence for this comes from studies on latent inhibition (LI), referring to the phenomenon that prior exposure to a stimulus impedes learning about the relationship between that stimulus and an outcome.

Design

This article reviewed all published studies examining the relationship between LI and both schizophrenia and schizotypy.

Results

Contemporary literature suggests that LI is attenuated in both people with schizophrenia and those loading highly on measures of schizotypy, the multidimensional derivative of schizophrenia. This suggests that these individuals assign greater salience to stimuli than healthy controls and people scoring low on measures of schizotypy, respectively. However, several confounds limit these conclusions. Studies on people with schizophrenia are limited by the confounding effects of psychotropic medications, idiosyncratic parsing of samples, variation in dependent variables, and lack of statistical power. Moreover, LI paradigms are limited by the confounding effects of learned irrelevance, conditioned inhibition, negative priming, and novel pop-out effects.

Conclusions

This review concludes with the recommendation that researchers develop novel paradigms that overcome these limitations to evaluate the predictions of the Salience Hypothesis.

Reviewing the Potential Therapeutic Approaches Targeting the Modulation of Gastrointestinal Microflora in Schizophrenia

Schizophrenia (SCZ) is a severe brain disorder characterized by an intriguing clinical panel that has begun to gain interest due to its particular phenotype. Having considered the role of gut microflora in psychiatry, the latest discoveries might offer further insight into the underlying mechanisms. Thus, we aimed to offer an updated overview of the therapeutic potential of microorganism-derived supplements alongside dedicated protocols that target the re-establishment of the host's eubiosis. Based on combinations of specific keywords, we performed searches in four databases (PubMed/Medline, ISI Web of Knowledge, Scopus, and ScienceDirect) for the established interval (2018-2022) and identified twenty two eligible cases, restricted only to human patients' experiences. Up until the writing of this manuscript, it has been revealed that the administration of specific lactic acid bacteria strains (Lactobacillus and Bifidobacterium), or those combined with vitamin D and selenium, maintain the integrity of the gut flora, preventing antagonistic effects including inflammation, antipsychotic-related body weight gain (olanzapine) and other metabolic dysfunctionalities. However, there are multiple antipsychotics that exert a potent effect upon gut flora, influencing a plethora of pathways and creating a dysbalance ratio between beneficial and opportunistic pathogens. Risperidone, amisulpride, and clozapine are just a few examples, but the current literature is unfortunately inconsistent and reported data is contradictory, which is why we support additional studies in this context. Moreover, we further argue the utility of studying how distinct controlled substances influence microbial communities, considering that ketamine is proved to alleviate depressive-like behavior as opposed to amphetamine and phencyclidine, which are known substances to trigger SCZ-like symptoms in experimental models. Probiotics may be regarded as the most consequential vehicle through which the gut flora can be successfully influenced, in adequate doses exerting a beneficial role as an alternative approach to alleviate SCZ symptoms.

Place of the partial dopamine receptor agonist aripiprazole in the management of schizophrenia in adults: a Delphi consensus study

BACKGROUND

Aripiprazole is a second-generation antipsychotic, efficacious in patients with schizophrenia during acute episodes. Due to its pharmacological profile, aripiprazole may be of interest in patients with specific clinical profiles who have not been studied extensively in randomised clinical trials.

OBJECTIVES

To capture experience with aripiprazole in everyday psychiatric practice using the Delphi method in order to inform decision-making on the use of aripiprazole for the treatment of patients with schizophrenia in clinical situations where robust evidence from clinical trials is lacking.

METHODS

The scope of the survey was defined as the management of schizophrenia in adults. A systematic literature review was performed to identify the different clinical situations in which aripiprazole has been studied, and to describe the level of clinical evidence. Clinical profiles to include in the Delphi survey were selected if there was a clear interest in terms of medical need but uncertainty over the efficacy of aripiprazole. For each clinical profile retained, five to seven specific statements were generated and included in a questionnaire. The final 41-item questionnaire was proposed to a panel of 406 French psychiatrists with experience in the treatment of schizophrenia. Panellists rated their level of agreement using a Likert scale. A second round of voting on eleven items was organised to clarify points for which a consensus was not obtained in the first round.

RESULTS

Five clinical profiles were identified in the literature review (persistent negative symptoms, pregnancy, cognitive dysfunction, addictive comorbidity and clozapine resistance). Sixty-two psychiatrists participated in the first round of the Delphi survey and 33 in the second round. A consensus was obtained for 11 out of 41 items in the first round and for 9/11 items in the second round. According to the panellists' clinical experience, aripiprazole can be used as maintenance treatment for pregnant women, is relevant to preserve cognitive function and can be considered an option in patients with a comorbid addictive disorder or with persistent negative symptoms.

CONCLUSION

These findings may help physicians in choosing relevant ways to use aripiprazole and highlight areas where more research is needed to widen the evidence base.

Primary and Secondary Negative Symptoms in Schizophrenia

The negative symptoms of schizophrenia include volitional (motivational) impairment manifesting as avolition, anhedonia, social withdrawal, and emotional disorders such as alogia and affective flattening. Negative symptoms worsen patients' quality of life and functioning. From the diagnostic point of view, it is important to differentiate between primary negative symptoms, which are regarded as an integral dimension of schizophrenia, and secondary negative symptoms occurring as a result of positive symptoms, comorbid depression, side effects of antipsychotics, substance abuse, or social isolation. If secondary negative symptoms overlap with primary negative symptoms, it can create a false clinical impression of worsening deficit symptoms and disease progression, which leads to the choice of incorrect therapeutic strategy with excessive dopamine blocker loading. Different longitudinal trajectories of primary and secondary negative symptoms in different schizophrenia stages are proposed as an important additional discriminating factor. This review and position paper focuses primarily on clinical aspects of negative symptoms in schizophrenia, their definition, phenomenology, factor structure, and classification. It covers the historical and modern concepts of the paradigm of positive and negative symptoms in schizophrenia, as well as a detailed comparison of the assessment tools and psychometric tests used for the evaluation of negative symptoms.

Disentangling the symptoms of schizophrenia: Network analysis in acute phase patients and in patients with predominant negative symptoms

Background

The Positive and Negative Syndrome Scale (PANSS) is widely used in schizophrenia and has been divided into distinct factors (5-factor models) and subfactors. Network analyses are newer in psychiatry and can help to better understand the relationships and interactions between the symptoms of a psychiatric disorder. The aim of this study was threefold: (a) to evaluate connections between schizophrenia symptoms in two populations of patients (patients in the acutely exacerbated phase of schizophrenia and patients with predominant negative symptoms [PNS]), (b) to test whether network analyses support the Mohr 5 factor model of the PANSS and the Kahn 2 factor model of negative symptoms, and finally (c) to identify the most central symptoms in the two populations.

Methods

Using pooled baseline data from four cariprazine clinical trials in patients with acute exacerbation of schizophrenia (n = 2193) and the cariprazine–risperidone study in patients with PNS (n = 460), separate network analyses were performed. Network structures were estimated for all 30 items of the PANSS.

Results

While negative symptoms in patients with an acute exacerbation of schizophrenia are correlated with other PANSS symptoms, these negative symptoms are not correlated with other PANSS symptoms in patients with PNS. The Mohr factors were partially reflected in the network analyses. The two most central symptoms (largest node strength) were delusions and uncooperativeness in acute phase patients and hostility and delusions in patients with PNS.

Conclusions

This network analysis suggests that symptoms of schizophrenia are differently structured in acute and PNS patients. While in the former, negative symptoms are mainly secondary, in patients with PNS, they are mainly primary. Further, primary negative symptoms are better conceptualized as distinct negative symptom dimensions of the PANSS.

Mechanisms Underlying Motivational Dysfunction in Schizophrenia

Negative symptoms are a debilitating feature of schizophrenia which are often resistant to pharmacological intervention. The mechanisms underlying them remain poorly understood, and diagnostic methods rely on phenotyping through validated questionnaires. Deeper endo-phenotyping is likely to be necessary in order to improve current understanding. In the last decade, valuable behavioural insights have been gained through the use of effort-based decision making (EBDM) tasks. These have highlighted impairments in reward-related processing in schizophrenia, particularly associated with negative symptom severity. Neuroimaging investigations have related these changes to dysfunction within specific brain networks including the ventral striatum (VS) and frontal brain regions. Here, we review the behavioural and neural evidence associated with negative symptoms, shedding light on potential underlying mechanisms and future therapeutic possibilities. Findings in the literature suggest that schizophrenia is characterised by impaired reward based learning and action selection, despite preserved hedonic responses. Associations between amotivation and reward-processing deficits have not always been clear, and may be mediated by factors including cognitive dysfunction or dysfunctional or self-defeatist beliefs. Successful endo-phenotyping of negative symptoms as a function of objective behavioural and neural measurements is crucial in advancing our understanding of this complex syndrome. Additionally, transdiagnostic research–leveraging findings from other brain disorders, including neurological ones–can shed valuable light on the possible common origins of motivation disorders across diseases and has important implications for future treatment development.

Hippocampal subfield transcriptome analysis in schizophrenia psychosis

We have previously demonstrated functional and molecular changes in hippocampal subfields in individuals with schizophrenia (SZ) psychosis associated with hippocampal excitability. In this study, we use RNA-seq and assess global transcriptome changes in the hippocampal subfields, DG, CA3, and CA1 from individuals with SZ psychosis and controls to elucidate subfield-relevant molecular changes. We also examine changes in gene expression due to antipsychotic medication in the hippocampal subfields from our SZ ON- and OFF-antipsychotic medication cohort. We identify unique subfield-specific molecular profiles in schizophrenia postmortem samples compared with controls, implicating astrocytes in DG, immune mechanisms in CA3, and synaptic scaling in CA1. We show a unique pattern of subfield-specific effects by antipsychotic medication on gene expression levels with scant overlap of genes differentially expressed by SZ disease effect versus medication effect. These hippocampal subfield changes serve to confirm and extend our previous model of SZ and can explain the lack of full efficacy of conventional antipsychotic medication on SZ symptomatology. With future characterization using single-cell studies, the identified distinct molecular profiles of the DG, CA3, and CA1 in SZ psychosis may serve to identify further potential hippocampal-based therapeutic targets.

[History and current state of the problem of negative disorders (research of nosological period)]

Pioneers of nosology in psychiatry considered mental deficit as a basic disorder obligated to all clinical forms of illness, as did E. Kraepelin in the concept of dementia praecox and E. Bleuler in the concept of schizophrenia. At the present stage of studies, this position is clearly articulated in the «deficit schizophrenia» concept of J. Klosterkotter. Negative disorders are considered in categorical approach to interpret psychopathological dimensions of schizophrenia as coordinated, strongly bound with positive syndromes (concept of «dialectical unity» of A.V. Snezhnevskiy, 1964) and classified as syndromes according to systematics of positive disorders. However, distinguished types of negative disorders are determined in terms of positive syndromes or characterological changes (asthenic, pseudopsychopathic deficit). Within a new paradigm (dimensional approach to schizophrenia), which differs from the categorical approach, negative disorders are considered as a distinct domain, primary in relation to other psychopathological phenomena of schizophrenia). A concept of primary persistent negative symptoms serves as basis of the current concept of schizophrenic deficit. Factor analysis revealed two domains of negative disorders: 1) emotional blunting: blunted affect, alogia; 2) avolition: apathy, anhedonia, asociality.

Negative Symptoms of Schizophrenia: New Prospects of Cariprazine Treatment

Background

Cariprazine is a new piperazine derivative atypical antipsychotic, like aripiprazole and brexpiprazole. It has been approved for treating schizophrenia in many countries and has recently been included on the List of Essential Medicines in Russia. Unlike most other atypical antipsychotics, it shows high in vivo occupancy of dopamine D2 and D3 receptors at clinically relevant doses. In animal models, cariprazine has demonstrated dopamine D3 receptor-dependent pro-cognitive and anti-anhedonic effects, suggesting its potential for treating negative symptoms. This review summarizes the efficacy of cariprazine in the treatment of negative symptoms of schizophrenia.

Methods

A literature search of databases covering international and Russian journals, for articles published between 1st January 2010 and 1st June 2020.

Results

Cariprazine demonstrated at least comparable efficacy in the treatment of schizophrenia symptoms to active comparators including risperidone, olanzapine or aripiprazole. The drug has a good safety profile. It appeared to be associated with a lower risk of metabolic syndromes and most extrapyramidal symptoms. The positive effect of cariprazine on the negative symptoms of schizophrenia may be associated with the elimination of secondary negative symptoms. However, of all the atypical antipsychotics to date, only cariprazine has a convincingly, methodologically robust proven advantage over risperidone in eliminating the predominant negative symptoms of schizophrenia. Yet only four studies have investigated the effect of cariprazine on the negative symptoms of schizophrenia. There is a lack of research into its direct impact on emotional-volitional disorders, anhedonia, cognitive symptoms and personality changes. However, there is evidence to suggest cariprazine is effective in treatment-resistant cases, but this requires further confirmation.

Conclusion

Cariprazine is an effective and well-tolerated agent for the treatment of schizophrenia and may be effective in cases where other antipsychotics have failed. Cariprazine has been shown to have a positive effect on negative symptoms. Further studies are needed to collect more data on long-term treatment of schizophrenia and especially negative symptoms.

[Negative and positive disorders of schizophrenia (issues of co-dependence, psychopathology and pathogenesis)]

The authors consider current and own conceptions about correlations of the processes underlying the pathogenesis of schizophrenia presented by negative and positive disorders. With growth of academic psychiatry, evaluation of a correlation between positive and negative dimensions has changed dramatically: on the one hand presenting in clinical unity - simultaneous psychopathologic structures, and on the other hand being clinically and pathogenetically heterogenic in dimensional structure. According to our clinical and biological findings and an analysis of fundamental neurobiological studies, positive and negative disorders present in the clinical picture of schizophrenia as two separate psychopathological and pathogenetic structures. A new paradigm of the correlation between positive and negative structures - the interaction between positive and deficit symptoms - reveals psychopathological functions differentiated for each of dimensional structures. Negative disorders act as «transformers» modifying characteristics of primary transnosological positive disorders to the level of psychopathological structures preferable for schizophrenia; positive disorders, in their turn, act as «moderators» augmenting, amplifying manifestations of negative symptoms. This psychopathological construct of the correlation between dimensional structures paves a way for the development of a new concept of psychopharmacological treatment of schizophrenic deficit: both negative symptoms and amplifying positive symptoms are considered as «target symptoms» for pharmacological interventions.

Validity and utility of Hierarchical Taxonomy of Psychopathology (HiTOP): I. Psychosis superspectrum

The Hierarchical Taxonomy of Psychopathology (HiTOP) is a scientific effort to address shortcomings of traditional mental disorder diagnoses, which suffer from arbitrary boundaries between psychopathology and normality, frequent disorder co-occurrence, heterogeneity within disorders, and diagnostic instability. This paper synthesizes evidence on the validity and utility of the thought disorder and detachment spectra of HiTOP. These spectra are composed of symptoms and maladaptive traits currently subsumed within schizophrenia, other psychotic disorders, and schizotypal, paranoid and schizoid personality disorders. Thought disorder ranges from normal reality testing, to maladaptive trait psychoticism, to hallucinations and delusions. Detachment ranges from introversion, to maladaptive detachment, to blunted affect and avolition. Extensive evidence supports the validity of thought disorder and detachment spectra, as each spectrum reflects common genetics, environmental risk factors, childhood antecedents, cognitive abnormalities, neural alterations, biomarkers, and treatment response. Some of these characteristics are specific to one spectrum and others are shared, suggesting the existence of an overarching psychosis superspectrum. Further research is needed to extend this model, such as clarifying whether mania and dissociation belong to thought disorder, and explicating processes that drive development of the spectra and their subdimensions. Compared to traditional diagnoses, the thought disorder and detachment spectra demonstrated substantially improved utility: greater reliability, larger explanatory and predictive power, and higher acceptability to clinicians. Validated measures are available to implement the system in practice. The more informative, reliable and valid characterization of psychosis-related psychopathology offered by HiTOP can make diagnosis more useful for research and clinical care.

Principal-component analysis of PANSS and SANS - SAPS global ratings in schizophrenic patients

The aim of this study was to test whether a positive and a negative component could be found in broadly defined schizophrenic patients. Therefore, 70 patients either in an exacerbated or in a stabilized phase were selected according to the criteria of at least 1 of the 4 following diagnostic systems: DSM III-R, Schneider, Carpenter, Langfeldt; principal component analyses (PCA) were carried out with the 9 global ratings of the Scales for Assessment of Negative and Positive Symptoms (SANS and SAPS) and with the Positive and Negative Syndrome Scale (PANSS). The PCA of the SANS-SAPS global ratings yielded a 3-factor solution explaining 72.14% of the total variance, depicting a negative, a positive and a disorganization component. The PCA of the PANSS provided a 5-factor solution with a total explained variance of 55.98%. The first 3 factors were similar to those of the SANS-SAPS global rating analysis. The results showed that the positive and negative components described in a homogeneous schizophrenic population could be replicated in a larger and more heterogeneous group of schizophrenic patients. The question regarding the sufficiency of the positive-negative dichotomy was strengthened by the presence of a third disorganization component which explained as much of the variance as the positive component.

Principal-component analyses of PANSS and SANS-SAPS in schizophrenia: their stability in an acute phase

Whether studies agree or disagree on the positive-negative dichotomy in schizophrenia, the relevance of a third component, disorganization, remains a point of debate. Disorganization, as expressed by the scale for the assessment of negative symptoms and positive symptoms (SANS-SAPS) and the positive and negative syndrome scale (PANSS) principal-component analyses, could be considered as permanent and determinant a dimension as the positive and negative components. The aim of this study therefore was to determine whether this disorganization, with the negative and positive components, is stable and has the same composition in the acute and postacute phases of illness. This study was carried out in 57 patients, broadly defined by at least one of four diagnostic criteria (American Psychiatric Association, Langfeldt, Carpenter and Schneider), established with a computerized checklist, and evaluated with SANS-SAPS and PANSS. Principal component analyses (PCA) of these scales were performed at admission and discharge from hospital.

The PCA of SANS-SAPS displayed a 3-factor solution, regardless of the phase of illness (acute or postacute), showing that the negative, positive and disorganization components were stable. The PCA of PANSS yielded negative and positive components perfectly stable over time and a disorganization component whose composition varied between admission and discharge. At admission, this component included the conceptual disorganization item negatively correlated with one of depression. At discharge, this disorganization component included two additional items, autistic preoccupation and mannerisms and one depression component appeared. The instability of the PCA of PANSS could express the role played by the phase of illness; in an acute phase, this disorganization component was constituted by more “positive” items such as grandiosity, unusual thought content and active social avoidance whereas in the postacute phase, it included items that reflected more the chronicity of the illness, such as mannerisms and autistic preoccupation. Moreover, the depressive item appeared, in the postacute phase, in a specific depressive component. This result could be due to the fact that depressive symptoms cannot be expressed when positive symptoms are very severe, which explains why no depressive components were shown during the acute phase.

Schizophrenia Infrastructures: Local and Global Dynamics of Transformation in Psychiatric Diagnosis-Making in the Twentieth and Twenty-First Centuries

This article uses the concept of "diagnosis infrastructures" to propose a framework for narrating the history of schizophrenia as a global category in the twentieth century. Diagnosis infrastructures include the material and architectural arrangements, legal requirements, and professional models that enable both the ways in which patients come to clinics and navigate the world of schizophrenia as well as the means through which clinicians organize their diagnostic work. These infrastructures constitute a framework for how schizophrenia has been identified as a disorder. This article explores three moments in the history of schizophrenia infrastructures in the twentieth century. The first is the German psychiatrist Kurt Schneider's discussion of first- and second-rank symptoms in the interwar period. The second is the research on criteria for defining schizophrenia within the framework of the WHO International Pilot Study of Schizophrenia at the turn of the 1970s. The third corresponds to the changing infrastructures of mental health care in the context of both global mental health and the changing landscape of schizophrenia research over the last decades.

A Systematic Review of the Effect of Probiotic Supplementation on Schizophrenia Symptoms

BACKGROUND

Derangements of the gut microbiome have been linked to increased systemic inflammation and central nervous system disorders, including schizophrenia. This systematic review thus aimed to investigate the hypothesis that probiotic supplementation improves schizophrenia symptoms.

METHODS

By using the keywords (probiotic OR gut OR microbiota OR microbiome OR yogurt OR yoghurt OR lactobacillus OR bifidobacterium) AND (schizophrenia OR psychosis), a preliminary search of the PubMed, Medline, Embase, Google Scholar, ClinicalTrials.gov, Clinical Trials Register of the Cochrane Collaboration Depression, Anxiety and Neurosis Group (CCDANTR), and Cochrane Field for Complementary Medicine databases yielded 329 papers published in English between January 1, 1960 and May 1, 2018. Attempts were made to search grey literature as well.

RESULTS

Three clinical studies were reviewed, comparing the use of probiotics to placebo controls. Applying per-protocol analysis and a fixed-effects model, there was no significant difference in schizophrenia symptoms between the group that received probiotic supplementation and the placebo group post-intervention as the standardized mean difference was -0.0884 (95% CI -0.380 to 0.204, p = 0.551). Separate analyses were performed to investigate the effect of probiotic supplementation on positive or negative symptoms of schizophrenia alone. In both instances, no significant difference was observed as well.

CONCLUSION

Based on current evidence, limited inferences can be made regarding the efficacy of probiotics in schizophrenia. Although probiotics may have other benefits, for example to regulate bowel movement and ameliorate the metabolic effects of antipsychotic medications, the clinical utility of probiotics in the treatment of schizophrenia patients remains to be validated by future clinical studies.

Persistent negative symptoms in individuals at Ultra High Risk for psychosis

Persistent negative symptoms (PNS) defined as negative symptoms that persist for at least six months in the absence of high levels of positive, depressive and extrapyramidal symptoms, are evident early in the course of schizophrenia from the first episode of psychosis. However, their presence even earlier in the illness, in those at Ultra High Risk of psychosis, has not been investigated. In this study, we examined the prevalence, baseline correlates and outcome of PNS in 363 Ultra High Risk individuals. Assessments were conducted at baseline and 2-14 years later (mean follow up time 7.4 years). Baseline assessments included demographic, clinical and neurocognitive measures, which were repeated at follow up. The prevalence of PNS in the UHR group was 6.1%. Poor premorbid social adjustment, deficits in verbal fluency and childhood maltreatment, specifically emotional neglect, were evident at baseline in the PNS group compared to the group without PNS. PNS were associated with poor psychosocial functioning and deficits in processing speed at follow up. Our findings suggest that PNS can be detected early, allowing for the identification of a subset of Ultra High Risk patients who are likely to have poor outcome. These individuals could be the target for specific intervention. Further research is needed into the pathophysiology of these PNS to develop specific interventions.

Positive and negative symptoms in schizophrenia: A longitudinal analysis using latent variable structural equation modelling

BACKGROUND

Recent network models of schizophrenia propose it is the consequence of mutual interaction between its symptoms. While cross-sectional associations between negative and positive symptoms are consistent with this idea, they may merely reflect their involvement in the diagnostic process. Longitudinal analyses however may allow the identification of possible causal relationships. The European Schizophrenia Cohort (EuroSC) provides data suitable for this purpose.

METHODS

EuroSC includes 1208 patients randomly sampled from outpatient services in France, Germany and the UK. Initial measures were repeated after 12 and 24 months. Latent variable structural equation modelling was used to investigate the direction of effect between positive and negative symptoms assessed with the Positive and Negative Syndrome Scale, controlling for the effects of depressed mood and antipsychotic medication.

RESULTS

The structural model provided acceptable overall fit [χ² (953) = 2444.32, P < 0.001; CFI = 0.909; RMSEA = 0.046 (90% CI: 0.043, 0.048); SRMR = 0.052]. Both positive and negative symptoms were persistent, and strongly auto-correlated. There were also persistent cross-sectional associations between positive and negative symptoms. While the path from latent positive to negative symptoms from T1 to T2 approached conventional levels of statistical significance (P = 0.051), that from T2 to T3 did not (P = 0.546). Pathways in the reverse direction were uniformly non-significant.

CONCLUSIONS

There was no evidence that negative symptoms predict later positive symptoms. The prediction of negative symptoms by positive symptoms was ambiguous. We discuss implications for conceptualization of schizophrenic processes.

Pilot Validation Study of the Japanese Translation of the Brief Negative Symptoms Scale (BNSS)

PURPOSE

The brief negative symptoms scale (BNSS) is a concise instrument used to assess negative symptoms of subjects with schizophrenia covering five domains of negative symptoms and is suitable for use in clinical, experimental, and epidemiological settings. The original and translated version of BNSS has thus far been shown to have adequate psychometric properties. This study aimed to examine internal consistency, inter-rater and test-retest reliability, discriminant and convergent validity, and factor structure of the Japanese version of BNSS.

PATIENTS AND METHODS

The assessment was performed by 11 raters using interview videos of nine subjects. Reliability was calculated with Cronbach's alpha for internal consistency and intra class correlation coefficient (ICC) for inter-rater reliability. Pearson's correlation coefficients were calculated to estimate the test-retest reliability. In addition to BNSS, Scale for assessment of negative symptoms (SANS) and scale for assessment of positive symptoms (SAPS) was obtained to assess the convergent and discriminant validity. Factor structure was assessed using principle factor analysis.

RESULTS

The Japanese BNSS showed excellent internal consistency (Cronbach's alpha=0.95), inter-rater reliability (intra class correlation coefficient=0.97), and test-retest reliability (r=0.94, p<0.001). The convergent validity shown by correlation with SANS total score (r=0.87, p<0.001) and discriminant validity shown by correlation with SAPS total score (r=0.17, p=-0.68) were also good. Principal factor analysis revealed a two-factor structure of BNSS, although the loading of each item differed from that in the literature.

CONCLUSION

Our pilot study demonstrated that Japanese BNSS had good psychometric properties which were achieved with relatively brief training. Further studies with more subjects and raters with various backgrounds recruited from multiple sites are warranted.

Negative Symptoms in Early-Onset Psychosis and Their Association With Antipsychotic Treatment Failure

The prevalence of negative symptoms (NS) at first episode of early-onset psychosis (EOP), and their effect on psychosis prognosis is unclear. In a sample of 638 children with EOP (aged 10-17 y, 51% male), we assessed (1) the prevalence of NS at first presentation to mental health services and (2) whether NS predicted eventual development of multiple treatment failure (MTF) prior to the age of 18 (defined by initiation of a third trial of novel antipsychotic due to prior insufficient response, intolerable adverse-effects or non-adherence). Data were extracted from the electronic health records held by child inpatient and community-based services in South London, United Kingdom. Natural Language Processing tools were used to measure the presence of Marder Factor NS and antipsychotic use. The association between presenting with ≥2 NS and the development of MTF over a 5-year period was modeled using Cox regression. Out of the 638 children, 37.5% showed ≥2 NS at first presentation, and 124 (19.3%) developed MTF prior to the age of 18. The presence of NS at first episode was significantly associated with MTF (adjusted hazard ratio 1.62, 95% CI 1.07-2.46; P = .02) after controlling for a number of potential confounders including psychosis diagnostic classification, positive symptoms, comorbid depression, and family history of psychosis. Other factors associated with MTF included comorbid autism spectrum disorder, older age at first presentation, Black ethnicity, and family history of psychosis. In EOP, NS at first episode are prevalent and may help identify a subset of children at higher risk of responding poorly to antipsychotics.

Factor analysis of symptom dimensions (psychotic, affective and obsessive compulsive symptoms) in schizophrenia

AIM

To carryout factor analysis of symptom profile of patients with schizophrenia assessed by using positive and negative syndrome scale (PANSS), Calgary depression rating scale (CDSS), Young mania rating scale (YMRS) and YBOCS checklist.

METHODOLOGY

181 patients of schizophrenia were assessed on PANSS, CDSS, YMRS and YBOCS checklist.

RESULTS

Factor analysis of PANSS yielded 3 factor structure (positive, negative, anxiety). When the items of CDSS were added to the PANSS items, total number of factors increased to 4 with depression emerging as a separate factor. Addition of YMRS to PANSS and CDSS led to emergence of 5 factor model. Further addition of YBOCS checklist led to emergence of a 7 factor model (positive, depressive, obsessive compulsive, negative, manic, anxiety and obsessive compulsive-2), which explained 49.85% variance of the data. Positive symptoms emerged as the factor-1. Depressive symptoms loaded on the factor-2, negative symptoms loaded on to factor-4, manic symptoms loaded onto factor-5 and anxiety symptoms loaded onto factor-6. OC symptoms loaded onto factor 3 and 7.

CONCLUSIONS

Present study suggests that when multiple scales are used for assessment of various symptoms of schizophrenia, the symptoms separate out into 7 factors. This finding suggests that clinical assessment of schizophrenia should not be limited to core psychotic symptoms only and structured instruments must be used to elicit other symptoms too while monitoring the clinical picture of patients with schizophrenia.

Antipsychotic drugs for patients with schizophrenia and predominant or prominent negative symptoms: a systematic review and meta-analysis

BACKGROUND

Negative symptoms are the core of schizophrenia, but whether antipsychotics are efficacious for their treatment is unclear. Moreover, there is debate whether patients in relevant trials should have predominant negative symptoms or whether prominent negative symptoms are also acceptable.

METHODS

We systematically reviewed randomised, blinded antipsychotic drug trials in patients with schizophrenia and either predominant or prominent negative symptoms (last search Dec 12, 2017). Separate pairwise meta-analyses were conducted in these two populations. The primary outcome was negative symptoms. Depressive, symptoms, positive symptoms, and extrapyramidal side-effects were analysed as causes of secondary negative symptoms.

FINDINGS

We included 21 randomized-controlled trials with 3451 participants which revealed the following significant differences in the primary outcome: in patients with predominant negative symptoms amisulpride was superior to placebo (N = 4; n = 590, SMD 0.47, CI 0.23, 0.71), olanzapine was superior to haloperidol in a small trial (n = 35) and cariprazine outperformed risperidone (N = 1, n = 456, SMD - 0.29, CI - 0.48, - 0.11). In patients with prominent negative symptoms, olanzapine and quetiapine were superior to risperidone in single trials. Overall, studies in prominent negative symptoms were potentially more confounded by improvements of secondary negative symptoms.

INTERPRETATION

Amisulpride is the only antipsychotic that outperformed placebo in the treatment of predominant negative symptoms, but there was a parallel reduction of depression. Cariprazine was better than risperidone in a large trial that was well-controlled for secondary negative symptoms, but the trial was sponsored by its manufacturer. Future trials should apply scientifically developed definitions such as the deficit syndrome and the persistent negative symptoms concept.

Schizotypy, Schizotypic Psychopathology, and Schizophrenia: Hearing Echoes, Leveraging Prior Advances, and Probing New Angles

The nature and definition of schizotypy, as the latent liability for schizophrenia capable of generating various phenotypic and endophenotypic outcomes, is reviewed. The proceedings of the 2017 meeting of the International Consortium on Schizotypy Research are included in this Special Section and they are presented as illustrations of current research work on schizotypy. The potential leverage of the schizotypy framework for schizophrenia research continues to be realized and these articles present current research efforts that explore new angles of inquiry while building upon past advances. Methodological and substantive areas of concern are highlighted and suggestions for improvement of future schizotypy research are made.

Correspondence between negative symptoms and potential sources of secondary negative symptoms over time

There has been a debate in the literature about the distinction between primary and secondary negative symptoms of schizophrenia. Our aim was to study the associations between negative symptoms and potential sources of secondary negative symptoms over time. A sample of 275 participants with at least mid-moderate negative symptoms was randomized into body psychotherapy or Pilates class in a previous study. No significant differences were found between groups over time and changes in the symptom domains were modest. The present investigation considers the longitudinal correlation between variables of interest at baseline, 3 and 9 months follow-up. Measures were the Clinical Assessment Interview for Negative Symptoms (CAINS), the Positive and Negative Symptom Scale (PANSS), the Calgary Depression Scale (CDSS) and the Simpson-Angus Extrapyramidal side-effects Scale (SAS). Mixed models were computed to test the longitudinal association between these variables. In a sensitivity analysis, the dosages of antipsychotic, illness duration and allocated intervention were taken into account. Overall, the course of extrapyramidal side-effects, depressive and positive symptoms was significantly related to the course of negative symptoms. Only extrapyramidal effects were longitudinally correlated to expressive negative symptoms. The sensitivity analyses showed unaltered results for positive symptoms and depression but a lack of association between extrapyramidal effects and the CAINS outcomes. In conclusion, the unambiguous interpretation between primary and secondary negative symptoms may lead to refined treatment approaches for schizophrenia and to increased effects of the interventions.

Salivary biomarkers for the diagnosis and monitoring of neurological diseases

Current research efforts on neurological diseases are focused on identifying novel disease biomarkers to aid in diagnosis, provide accurate prognostic information and monitor disease progression. With advances in detection and quantification methods in genomics, proteomics and metabolomics, saliva has emerged as a good source of samples for detection of disease biomarkers. Obtaining a sample of saliva offers multiple advantages over the currently tested biological fluids as it is a non-invasive, painless and simple procedure that does not require expert training or harbour undesirable side effects for the patients. Here, we review the existing literature on salivary biomarkers and examine their validity in diagnosing and monitoring neurodegenerative and neuropsychiatric disorders such as autism and Alzheimer's, Parkinson's and Huntington's disease. Based on the available research, amyloid beta peptide, tau protein, lactoferrin, alpha-synuclein, DJ-1 protein, chromogranin A, huntingtin protein, DNA methylation disruptions, and micro-RNA profiles provide display a reliable degree of consistency and validity as disease biomarkers.