White matter, cognition and psychotic-like experiences in UK Biobank

Cognitive functioning in people with psychotic experiences: a systematic review and meta-analysis study

Earlier research suggested that psychotic experiences (PEs), the extended-psychosis phenotype, are associated with cognitive impairment. Recent studies, however, revealed more mixed findings, and patterns and magnitude of cognitive deficits in PEs remain uncertain. We aimed to systematically review and quantitatively synthesize estimates of cognitive functioning covering a wide array of domains in individuals with versus without PEs. We systematically searched four databases from inception to 6 July 2023. We generated pooled effect size (Hedges'g) using random-effects models. Subgroup analyses and meta-regression examining the moderating effect of sex, age at PE assessment, study design, cognitive task, and PE assessment instrument on cognitive functioning were performed when applicable. The study was registered with PROSPERO (CRD42023442528). Twenty-seven and six studies were included for meta-analysis of cognitive functioning comparing individuals with versus without PEs (n = 82,561; 10,251 individuals with PEs) and individuals with high-level versus low-level PEs (n = 8062; 813 individuals with high-level PEs), respectively. Individuals with PEs exhibited worse cognitive performance in general cognition (Hedges'g = -0.10 [95%CI = -0.18 to -0.02]), verbal fluency (Hedges'g = -0.05 [95%CI = -0.10 to -0.00]), visual memory (Hedges'g = -0.21 [95%CI = -0.38 to -0.03]), and working memory (Hedges'g = -0.16 [95%CI = -0.28 to -0.04]). Meta-regression revealed that general cognition associated with PEs was related to younger age (z = 3.37, p = 0.001), male sex (z = -2.59, p = 0.010), and cognitive assessment before PE assessment (z = -2.15, p = 0.031), whereas working memory in individuals with PEs was associated with concurrent cognitive and PE assessment (z = 6.19, p < 0.001). We failed to find moderating effect of the choice of PE assessment instrument or cognitive task on cognitive functioning in PEs. Additional analysis showed no significant difference in the performance of any cognitive domains between individuals with high-level versus low-level PEs. Limitations included studies primarily derived from Western countries, no social-cognitive domains, and varied PE measurement. In sum, PEs are associated with milder and more circumscribed cognitive impairment relative to psychotic disorders. Future research is required to clarify differential cognitive trajectories between individuals with transient PEs and persistent/recurrent-PEs.

Psychosis superspectrum II: neurobiology, treatment, and implications

Alternatives to traditional categorical diagnoses have been proposed to improve the validity and utility of psychiatric nosology. This paper continues the companion review of an alternative model, the psychosis superspectrum of the Hierarchical Taxonomy of Psychopathology (HiTOP). The superspectrum model aims to describe psychosis-related psychopathology according to data on distributions and associations among signs and symptoms. The superspectrum includes psychoticism and detachment spectra as well as narrow subdimensions within them. Auxiliary domains of cognitive deficit and functional impairment complete the psychopathology profile. The current paper reviews evidence on this model from neurobiology, treatment response, clinical utility, and measure development. Neurobiology research suggests that psychopathology included in the superspectrum shows similar patterns of neural alterations. Treatment response often mirrors the hierarchy of the superspectrum with some treatments being efficacious for psychoticism, others for detachment, and others for a specific subdimension. Compared to traditional diagnostic systems, the quantitative nosology shows an approximately 2-fold increase in reliability, explanatory power, and prognostic accuracy. Clinicians consistently report that the quantitative nosology has more utility than traditional diagnoses, but studies of patients with frank psychosis are currently lacking. Validated measures are available to implement the superspectrum model in practice. The dimensional conceptualization of psychosis-related psychopathology has implications for research, clinical practice, and public health programs. For example, it encourages use of the cohort study design (rather than case-control), transdiagnostic treatment strategies, and selective prevention based on subclinical symptoms. These approaches are already used in the field, and the superspectrum provides further impetus and guidance for their implementation. Existing knowledge on this model is substantial, but significant gaps remain. We identify outstanding questions and propose testable hypotheses to guide further research. Overall, we predict that the more informative, reliable, and valid characterization of psychopathology offered by the superspectrum model will facilitate progress in research and clinical care.

Reduced anterior callosal white matter in risk for psychosis associated with processing speed as a fundamental cognitive impairment

BACKGROUND

Previous research in psychotic disorders discovered associations between reduced integrity of white matter (WM) in the corpus callosum (CC) and impaired cognitive functions, suggesting processing speed as a central construct. However, it is still largely unexplored to what extent disruption in callosal WM is related to cognitive deficits during the risk stage prior to psychosis.

METHODS

To address this gap, we measured the WM integrity in CC by fractional anisotropy (FA) and assessed cognition in 60 clinical-high risk for psychosis (CHR) patients during adolescence/young adulthood and 38 healthy control (HC) subjects. We employed tract based spatial statistics to examine group differences and associations between CC-FA and processing speed, executive function, and spatial working memory.

RESULTS

We revealed deficits in processing speed, executive function, and spatial working memory of CHR patients, and reductions in FA of the genu and the body of the CC (p < 0.05, corrected for multiple comparisons) compared to HC. A mediation analysis using the combined sample (CHR + HC) showed that processing speed mediates the associations between the impaired CC structure and executive function and spatial working memory, respectively. Exploratory analyses between CC-FA and the cognitive domains located associations of processing speed in the genu and the body of CC with distinct spatial distributions of executive function and spatial working memory.

CONCLUSION

We suggest processing speed as a subordinate cognitive factor contributing to the associations between callosal WM, executive function and working memory. These results extend findings in psychotic disorders to the prior risk stage.

Pathway-Based Polygenic Risk Scores for Schizophrenia and Associations With Reported Psychotic-like Experiences and Neuroimaging Phenotypes in the UK Biobank

Background

Schizophrenia is a heritable psychiatric disorder with a polygenic architecture. Genome-wide association studies have reported that an increasing number of risk-associated variants and polygenic risk scores (PRSs) explain 17% of the variance in the disorder. Substantial heterogeneity exists in the effect of these variants, and aggregating them based on biologically relevant functions may provide mechanistic insight into the disorder.

Methods

Using the largest schizophrenia genome-wide association study conducted to date, we associated PRSs based on 5 gene sets previously found to contribute to schizophrenia pathophysiology-postsynaptic density of excitatory synapses, postsynaptic membrane, dendritic spine, axon, and histone H3-K4 methylation-along with respective whole-genome PRSs, with neuroimaging (n > 29,000) and reported psychotic-like experiences (n > 119,000) variables in healthy UK Biobank subjects.

Results

Several variables were significantly associated with the axon gene-set (psychotic-like communications, parahippocampal gyrus volume, fractional anisotropy thalamic radiations, and fractional anisotropy posterior thalamic radiations (β range -0.016 to 0.0916, false discovery rate-corrected p [pFDR] ≤ .05), postsynaptic density gene-set (psychotic-like experiences distress, global surface area, and cingulate lobe surface area [β range -0.014 to 0.0588, pFDR ≤ .05]), and histone gene set (entorhinal surface area: β = -0.016, pFDR = .035). From these, whole-genome PRSs were significantly associated with psychotic-like communications (β = 0.2218, pFDR = 1.34 × 10-7), distress (β = 0.1943, pFDR = 7.28 × 10-16), and fractional anisotropy thalamic radiations (β = -0.0143, pFDR = .036). Permutation analysis revealed that these associations were not due to chance.

Conclusions

Our results indicate that genetic variation in 3 gene sets relevant to schizophrenia may confer risk for the disorder through effects on previously implicated neuroimaging variables. Because associations were stronger overall for whole-genome PRSs, findings here highlight that selection of biologically relevant variants is not yet sufficient to address the heterogeneity of the disorder.