The Kraepelian concept of schizophrenia: Dying but not yet dead

Transdiagnostic Neurocognitive Endophenotypes for Schizophrenia, Bipolar I Disorder and a Broad Psychosis/Bipolar I Disorder Phenotype: A Mega-Analysis of Twin and Sibling Data

BACKGROUND

Psychiatric research is increasingly embracing a paradigm shift from categorical diagnoses to neurobiologically meaningful dimensions that cross current diagnostic boundaries. This transposition calls for redefining endophenotypes to accommodate transdiagnostic vulnerabilities. We sought to identify shared and disorder-specific neurocognitive endophenotypes for schizophrenia, bipolar I disorder (BD-I) and a broad psychosis/BD-I phenotype in a mega-analysis of twin/sibling data.

STUDY DESIGN

We performed genetic model fitting to intelligence (IQ) and computerised neurocognitive data derived from 1050 twins/siblings from three research centres in the UK, Denmark and the Netherlands, affected (n = 257) or unaffected (n = 793) by schizophrenia, other primary psychoses and BD-I. We examined the endophenotypic status of IQ, spatial working memory (SWM), visual recognition, sustained attention/rapid visual processing (RVP), mental flexibility, and spatial planning/problem solving (all validated as endophenotypes for schizophrenia in previous studies) in relation to schizophrenia, BD-I and the broad phenotype.

STUDY RESULTS

After covarying for age, gender, education and research centre, IQ and SWM emerged as transdiagnostic endophenotypes, showing statistically significant heritabilities (h2 67-75% and 28-30%, respectively), phenotypic correlations (rph |0.14|-|0.25|) and genetic correlations (rg |0.18|-|0.42|) with all diagnostic phenotypes. Additionally, all remaining cognitive domains received validation as endophenotypes for the broad phenotype, and all, but RVP, for schizophrenia.

CONCLUSIONS

IQ and SWM tap into transdiagnostic elements of the genetic vulnerabilities to psychosis and BD-I. Our findings add to emergent evidence which spurs cautious optimism that a psychiatric nosology based on aetiology rather than phenotypical classifications may be feasible in the future, enabling biotyping and novel approaches to treatment.

First-Episode Psychosis incidence pre-, during, and post-COVID-19 pandemic: a six-year natural quasi-experimental study in South London

Background

The COVID-19 pandemic may have been accompanied by an increased exposure to psychosis risk factors. We used a pre-during-post study design to examine variations in the incidence of First-Episode Psychosis (FEP) before, during, and after the COVID-19 pandemic in South London. We hypothesised that FEP rates rose during the pandemic and subsequently returned to pre-pandemic levels.

Methods

Using the Clinical Record Interactive Search (CRIS) system, we screened individuals referred for FEP to Early Intervention Services for Psychosis (EISs) of the South London and Maudsley NHS Foundation Trust (SLaM) from 1 March 2018 to 29 February 2024. Population data for the SLaM catchment area were obtained from the Office for National Statistics (ONS). We calculated crude incidence rates and used Poisson regression models to estimate age-sex-ethnicity-adjusted variation in incidence by year (March-to-February) expressed as Incidence Rate Ratios (IRR).

Findings

A total of 3752 individuals experienced FEP during 5,487,858 person-years at risk, with a mean crude incidence of 68.4 per 100,000 person-years (95% CI: 66.2-70.6). The Poisson model showed a deviation from this mean at the peak of the COVID-19 pandemic in 2020/21, with FEP rates rising to 77.5 per 100,000 person-years (95% CI: 71.8-83.2) and similar rates in 2021/22. FEP incidence gradually returned to the pre-pandemic levels in the following years. During the COVID-19 pandemic, individuals of Black ethnicity experienced the greatest FEP increase, with an IRR of 1.45 (95% CI: 1.29-1.61) in 2020/21 and similar ratios in 2021/22. An increase was also observed in Asian individuals, with an IRR of 1.54 (95% CI: 1.20-1.88) in 2021/22, whereas no significant changes in incidence were observed for other ethnic groups across the pre-, during-, and post-pandemic periods.

Interpretation

FEP incidence in South London increased during the peak of the COVID-19 pandemic, particularly among Black and Asian individuals.

Funding

None.

A narrative review of nosology and the concept of schizophrenia: criticism and proposal

Schizophrenia diagnostics have evolved to adapt to clinical needs and scientific advances, and the current denominations emerged at the beginning of the twentieth century. Most problems arise while integrating clinical experiences, based on historical psychopathological descriptions, with emerging translational neuroscience research. This study aimed to evaluate the state-of-the-art critics of the current schizophrenia concept and their recommendations for new concepts. We performed a narrative review of the literature and searched for studies published in English in PubMed in the last 2 years which discussed the diagnosis of schizophrenia. Two authors independently selected the studies after analyzing the abstracts. Subsequently, studies were selected for this review by consensus. Twenty-six studies were selected, and all authors, except two, had restrictions on the current categorical model for the diagnosis of schizophrenia owing to the heterogeneity of symptomatology and high frequency of comorbidity. Eight studies proposed changes to the concept of schizophrenia. The central proposition was to adopt psychotic syndrome as a core feature instead of the current concept of schizophrenia. We synthesize these proposals using psychosis as a spectrum that includes schizophrenia as a more severe case at the end of the spectrum.

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 future of diagnosis in clinical neurosciences: Comparing multiple sclerosis and schizophrenia

The ongoing developments of psychiatric classification systems have largely improved reliability of diagnosis, including that of schizophrenia. However, with an unknown pathophysiology and lacking biomarkers, its validity still remains low, requiring further advancements. Research has helped establish multiple sclerosis (MS) as the central nervous system (CNS) disorder with an established pathophysiology, defined biomarkers and therefore good validity and significantly improved treatment options. Before proposing next steps in research that aim to improve the diagnostic process of schizophrenia, it is imperative to recognize its clinical heterogeneity. Indeed, individuals with schizophrenia show high interindividual variability in terms of symptomatic manifestation, response to treatment, course of illness and functional outcomes. There is also a multiplicity of risk factors that contribute to the development of schizophrenia. Moreover, accumulating evidence indicates that several dimensions of psychopathology and risk factors cross current diagnostic categorizations. Schizophrenia shares a number of similarities with MS, which is a demyelinating disease of the CNS. These similarities appear in the context of age of onset, geographical distribution, involvement of immune-inflammatory processes, neurocognitive impairment and various trajectories of illness course. This article provides a critical appraisal of diagnostic process in schizophrenia, taking into consideration advancements that have been made in the diagnosis and management of MS. Based on the comparison between the two disorders, key directions for studies that aim to improve diagnostic process in schizophrenia are formulated. All of them converge on the necessity to deconstruct the psychosis spectrum and adopt dimensional approaches with deep phenotyping to refine current diagnostic boundaries.

Copy Number Variations and Schizophrenia

Schizophrenia is a neurodevelopmental disorder with genetic and environmental factors involved in its aetiology. Genetic liability contributing to the development of schizophrenia is a subject of extensive research activity, as reliable data regarding its aetiology would enable the improvement of its therapy and the development of new methods of treatment. A multitude of studies in this field focus on genetic variants, such as copy number variations (CNVs) or single-nucleotide variants (SNVs). Certain genetic disorders caused by CNVs including 22q11.2 microdeletion syndrome, Burnside-Butler syndrome (15q11.2 BP1-BP2 microdeletion) or 1q21.1 microduplication/microdeletion syndrome are associated with a higher risk of developing schizophrenia. In this article, we provide a unifying framework linking these CNVs and their associated genetic disorders with schizophrenia and its various neural and behavioural abnormalities.

Schizophrenia: A Narrative Review of Etiopathogenetic, Diagnostic and Treatment Aspects

Although schizophrenia is currently conceptualized as being characterized as a syndrome that includes a collection of signs and symptoms, there is strong evidence of heterogeneous and complex underpinned etiological, etiopathogenetic, and psychopathological mechanisms, which are still under investigation. Therefore, the present viewpoint review is aimed at providing some insights into the recently investigated schizophrenia research fields in order to discuss the potential future research directions in schizophrenia research. The traditional schizophrenia construct and diagnosis were progressively revised and revisited, based on the recently emerging neurobiological, genetic, and epidemiological research. Moreover, innovative diagnostic and therapeutic approaches are pointed to build a new construct, allowing the development of better clinical and treatment outcomes and characterization for schizophrenic individuals, considering a more patient-centered, personalized, and tailored-based dimensional approach. Further translational studies are needed in order to integrate neurobiological, genetic, and environmental studies into clinical practice and to help clinicians and researchers to understand how to redesign a new schizophrenia construct.