Executive Dysfunctions in Schizophrenia: A Critical Review of Traditional, Ecological, and Virtual Reality Assessments

Impulsivity and inhibitory control in deficit and non-deficit schizophrenia

BACKGROUND

There is conflicting evidence on impulsivity and its potential relationship with inhibitory control in schizophrenia. This study therefore aimed to identify differences in impulsivity and cognitive and motor inhibition between patients with deficit (DS) and non-deficit (NDS) schizophrenia and healthy controls (HC). We also explored the relationships between impulsivity and different dimensions of inhibitory control in all studied groups.

METHODS

The sample comprised 28 DS patients, 45 NDS patients, and 39 age-matched HC. A neuropsychological battery was used.

RESULTS

DS patients scored lower in venturesomeness, while those with NDS scored higher in impulsiveness compared to HC. In addition, both groups of patients scored higher on measures of cognitive and motor inhibition, including those relatively independent of information processing speed (although the results were slightly different after adjusting for IQ and/or years of education). Correlations between impulsivity and cognitive inhibition emerged in DS patients, while links between impulsivity and motor inhibition were observed in HC.

CONCLUSIONS

Our results suggest the presence of deficits in experimentally assessed inhibitory control in schizophrenia patients, with predominant impulsivity in the NDS population. In addition, impulsivity may affect the cognitive control of inhibition in deficit schizophrenia. Nevertheless, due to the preliminary nature of these findings, they require further empirical verification in future research.

Assessing Executive Functioning in Schizophrenia: Concurrent and Discriminative Validity of a Novel Virtual Cooking Task

Deficits in executive functions (EF) are strongly related to real-life functioning and negative symptoms (NS) in schizophrenia. Recently, virtual reality has enabled more ecologically valid approaches to assess EF in simulated "real-life" scenarios among which the virtual cooking task (VCT) has gained attention. However, the clinical implications of the VCT in schizophrenia have not been investigated exhaustively. In this study, clinically stable individuals with schizophrenia (n = 38) and healthy controls (n = 42) completed a novel VCT and a set of computerized standard EF tools (CST) to primarily investigate concurrent and discriminant validity. In addition, the study explored links between EF assessments, functioning, and NS while controlling for antipsychotic intake, clinical stability, and age. This VCT consisted of four tasks with increasing difficulty and time constraints. The most relevant findings indicate that (1) the VCT showed moderate to strong correlations with CST, (2) the VCT discriminated EF performance between both the groups, (3) the VCT predicted interpersonal functioning, and (4) the VCT predicted NS in greater extent than CST. Accordingly, the findings give support to the concurrent and discriminant validity of the VCT to assess EF and indicate its value to deepen the study of collateral functional deficits and NS in schizophrenia.

Mindfulness-based interventions for patients with schizophrenia spectrum disorders: A systematic review of the literature

BACKGROUND

Mindfulness-based interventions (MBIs) have emerged as secular practices, including elements of mindfulness-based stress reduction (MBSR) and mindfulness-based cognitive therapy (MBCT). While MBIs have been widely adopted for physical and mental illness, only a few available programs are explicitly adapted for psychosis. However, previous reviews have reported the vital heterogeneity regarding treatment program structure. Therefore, this review aims to compare the structure of different mindfulness protocols applied to patients with schizophrenia spectrum disorder (SSD).

METHODS

A systematic search was conducted up to March 2023 in PubMed, Embase and PsycInfo. Following our protocol (CRD 42023253356), we followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) checklist.

RESULTS

We included 22 randomized controlled trials (RCTs) involving 1500 patients SSD. All programs varied in structure, session components, duration, and instructor experience. While MBSR-like programs focused on stress reactivity, MBCT-like programs addressed primary symptoms of psychosis and relapse prevention. Despite the heterogeneity of programs, some common mechanisms emerged, including attention training, emotion and stress regulation, decentering, self-compassion, and cognitive restructuring.

CONCLUSIONS

The critical heterogeneity found limits the interpretation of results. However, most recent trials present fewer risks of bias and more homogenous programs. Findings suggested potential benefits, such as reduced negative symptoms, increased well-being, and decreased hospitalization rates. For future studies, authors should align on more congruent MBIs programs for patients with SSD. Further research is needed to identify optimal mindfulness teaching approaches for patients with psychosis and investigate specific mechanisms of action, relevant processes, and optimal doses in varying settings.

Trans-ancestry meta-analysis of genome wide association studies of inhibitory control

Deficits in effective executive function, including inhibitory control are associated with risk for a number of psychiatric disorders and significantly impact everyday functioning. These complex traits have been proposed to serve as endophenotypes, however, their genetic architecture is not yet well understood. To identify the common genetic variation associated with inhibitory control in the general population we performed the first trans-ancestry genome wide association study (GWAS) combining data across 8 sites and four ancestries (N = 14,877) using cognitive traits derived from the stop-signal task, namely - go reaction time (GoRT), go reaction time variability (GoRT SD) and stop signal reaction time (SSRT). Although we did not identify genome wide significant associations for any of the three traits, GoRT SD and SSRT demonstrated significant and similar SNP heritability of 8.2%, indicative of an influence of genetic factors. Power analyses demonstrated that the number of common causal variants contributing to the heritability of these phenotypes is relatively high and larger sample sizes are necessary to robustly identify associations. In Europeans, the polygenic risk for ADHD was significantly associated with GoRT SD and the polygenic risk for schizophrenia was associated with GoRT, while in East Asians polygenic risk for schizophrenia was associated with SSRT. These results support the potential of executive function measures as endophenotypes of neuropsychiatric disorders. Together these findings provide the first evidence indicating the influence of common genetic variation in the genetic architecture of inhibitory control quantified using objective behavioural traits derived from the stop-signal task.