Executive function in schizophrenia: influence of substance use disorder history

The central executive network and executive function in healthy and persons with schizophrenia groups: a meta-analysis of structural and functional MRI

This meta-analysis evaluated the extent to which executive function can be understood with structural and functional magnetic resonance imaging. Studies included structural in schizophrenia (k = 8; n = 241) and healthy controls (k = 12; n = 1660), and functional in schizophrenia (k = 4; n = 104) and healthy controls (k = 12; n = 712). Results revealed a positive association in the brain behavior relationship when pooled across schizophrenia and control samples for structural (pr = 0.27) and functional (pr = 0.29) modalities. Subgroup analyses revealed no significant difference for functional neuroimaging (pr = .43, 95%CI = -.08-.77, p = .088) but with structural neuroimaging (pr = .37, 95%CI = -.08-.69, p = .015) the association to executive functions is lower in the control group. Subgroup analyses also revealed no significant differences in the strength of the brain-behavior relationship in the schizophrenia group (pr = .59, 95%CI = .58-.61, p = .881) or the control group (pr = 0.19, 95%CI = 0.18-0.19, p = 0.920), suggesting concordance.

Microstructural abnormalities in callosal fibers and their relationship with cognitive function in schizophrenia: A tract-specific analysis study

INTRODUCTION

The corpus callosum serves the essential role of relaying cognitive information between the homologous regions in the left and the right hemispheres of the brain. Cognitive impairment is a core dysfunction of schizophrenia, but much of its pathophysiology is unknown. The aim of this study was to elucidate the association between microstructural abnormalities of the corpus callosum and cognitive dysfunction in schizophrenia.

METHODS

We examined stepwise multiple regression analysis to investigate the relationship of the fractional anisotropy (FA) of callosal fibers in each segment with z-scores of each brief assessment of cognition in schizophrenia subtest and cognitive composite score in all subjects (19 patients with schizophrenia [SZ group] and 19 healthy controls [HC group]). Callosal fibers were separated into seven segments based on their cortical projection using tract-specific analysis of diffusion tensor imaging.

RESULTS

The FA of callosal fibers in the temporal segment was significantly associated with z-scores of token motor test, Tower of London test, and the composite score. In the SZ group, the FA of callosal fibers in the temporal segment was significantly associated with the z-score of the Tower of London test. In addition, the FA of callosal fibers in temporal segment showed significant negative association with the positive and negative syndrome scale negative score in the SZ group. Compared to the HC group, the FA in temporal segment was significantly decreased in the SZ group.

CONCLUSION

Our results suggest that microstructural abnormalities in the callosal white matter fibers connecting bilateral temporal lobe cortices contribute to poor executive function and severe negative symptom in patients with schizophrenia.

Early Substance Use Cessation Improves Cognition-10 Years Outcome in First-Episode Psychosis Patients

Background: Cognitive impairment may be a risk factor for, as well as a consequence of, psychosis. Non-remitting symptoms, premorbid functioning, level of education, and socioeconomic background are known correlates. A possible confounder of these associations is substance use, which is common among patients with psychosis and linked to worse clinical outcomes. Studies however show mixed results for the effect of substance use on cognitive outcomes. In this study, the long-term associations of substance use with cognition in a representative sample of first-episode psychosis patients were examined. Methods: The sample consisted of 195 patients. They were assessed for symptom levels, function, and neurocognition at 1, 2, 5, and 10 years after first treatment. Test scores were grouped into factor analysis-based indices: motor speed, verbal learning, visuomotor processing, verbal fluency, and executive functioning. A standardized composite score of all tests was also used. Patients were divided into four groups based on substance-use patterns during the first 2 years of treatment: persistent users, episodic users, stop-users, and nonusers. Data were analyzed using linear mixed effects modeling. Results: Gender, premorbid academic functioning, and previous education were the strongest predictors of cognitive trajectories. However, on motor speed and verbal learning indices, patients who stopped using substances within the first 2 years of follow-up improved over time, whereas the other groups did not. For verbal fluency, the longitudinal course was parallel for all four groups, while patients who stopped using substances demonstrated superior performances compared with nonusers. Persistent users demonstrated impaired visuomotor processing speed compared with nonusers. Within the stop- and episodic use groups, patients with narrow schizophrenia diagnoses performed worse compared with patients with other diagnoses on verbal learning and on the overall composite neurocognitive index. Discussion: This study is one of very few long-term studies on cognitive impairments in first-episode psychosis focusing explicitly on substance use. Early cessation of substance use was associated with less cognitive impairment and some improvement over time on some cognitive measures, indicating a milder illness course and superior cognitive reserves to draw from in recovering from psychosis.

Behavioral predictors of alcohol drinking in a neurodevelopmental rat model of schizophrenia and co-occurring alcohol use disorder

Alcohol use disorder commonly occurs in patients with schizophrenia and contributes greatly to its morbidity. Unfortunately, the neural and behavioral underpinnings of alcohol drinking in these patients are not well understood. In order to begin to understand the cognitive and reward-related changes that may contribute to alcohol drinking, this study was designed to address: 1) latent inhibition; 2) conditioning; and 3) extinction of autoshaping in a neurodevelopmental rat model with relevance to co-occurring schizophrenia and alcohol use disorders, the neonatal ventral hippocampal lesioned (NVHL) rat. NVHL lesions (or sham surgeries) were performed on post-natal day 7 (PND7) and animals were given brief exposure to alcohol during adolescent (PND 28-42). Latent inhibition of autoshaping, conditioning and extinction were assessed between PND 72-90. On PND90 animals were given alcohol again and allowed to establish stable drinking. Latent inhibition of autoshaping was found to be prolonged in the NVHL rats; the NVHL rats pre-exposed to the lever stimulus were slower to acquire autoshaping than sham pre-exposed rats. NVHL rats that were not pre-exposed to the lever stimulus did not differ during conditioning, but were slower to extinguish conditioned responding compared to sham controls. Finally, the NVHL rats from both groups drank significantly more alcohol than sham rats, and the extent of latent inhibition predicted future alcohol intake in the pre-exposed animals. These findings suggest that the latent inhibition of autoshaping procedure can be used to model cognitive- and reward-related dysfunctions in schizophrenia, and these dysfunctions may contribute to the development of co-occurring alcohol use.

A Comparison of Methamphetamine-Induced Psychosis and Schizophrenia: A Review of Positive, Negative, and Cognitive Symptomatology

Methamphetamine is a potent psychostimulant that can induce psychosis among recreational and chronic users, with some users developing a persistent psychotic syndrome that shows similarities to schizophrenia. This review provides a comprehensive critique of research that has directly compared schizophrenia with acute and chronic METH psychosis, with particular focus on psychiatric and neurocognitive symptomatology. We conclude that while there is considerable overlap in the behavioral and cognitive symptoms between METH psychosis and schizophrenia, there appears to be some evidence that suggests there are divergent aspects to each condition, particularly with acute METH psychosis. Schizophrenia appears to be associated with pronounced thought disorder, negative symptoms more generally and cognitive deficits mediated by the parietal cortex, such as difficulties with selective visual attention, while visual and tactile hallucinations appear to be more prevalent in acute METH-induced psychosis. As such, acute METH psychosis may represent a distinct psychotic disorder to schizophrenia and could be clinically distinguished from a primary psychotic disorder based on the aforementioned behavioral and cognitive sequelae. Preliminary evidence, on the other hand, suggests that chronic METH psychosis may be clinically similar to that of primary psychotic disorders, particularly with respect to positive and cognitive symptomatology, although negative symptoms appear to be more pronounced in schizophrenia. Limitations of the literature and avenues for future research are also discussed.

Unraveling Executive Functioning in Dual Diagnosis

In mental health, the term dual-diagnosis is used for the co-occurrence of Substance Use Disorder (SUD) with another mental disorder. These co-occurring disorders can have a shared cause, and can cause/intensify each other’s expression. Forming a threat to health and society, dual-diagnosis is associated with relapses in addiction-related behavior and a destructive lifestyle. This is due to a persistent failure to control impulses and the maintaining of inadequate self-regulatory behavior in daily life. Thus, several aspects of executive functioning like inhibitory, shifting and updating processes seem impaired in dual-diagnosis. Executive (dys-)function is currently even seen as a shared underlying key component of most mental disorders. However, the number of studies on diverse aspects of executive functioning in dual-diagnosis is limited. In the present review, a systematic overview of various aspects of executive functioning in dual-diagnosis is presented, striving for a prototypical profile of patients with dual-diagnosis. Looking at empirical results, inhibitory and shifting processes appear to be impaired for SUD combined with schizophrenia, bipolar disorder or cluster B personality disorders. Studies involving updating process tasks for dual-diagnosis were limited. More research that zooms in to the full diversity of these executive functions is needed in order to strengthen these findings. Detailed insight in the profile of strengths and weaknesses that underlies one’s behavior and is related to diagnostic classifications, can lead to tailor-made assessment and indications for treatment, pointing out which aspects need attention and/or training in one’s self-regulative abilities.

Are negative symptoms really related to cognition in schizophrenia?

Previous studies have generally found a relationship between negative and cognitive symptoms in schizophrenia. The present study investigated the relationship between the 5 PANSS factors of a recent consensus model developed by NIMH researchers, and cognitive performance as assessed with the MATRICS Consensus Cognitive Battery (MCCB) in 80 patients with schizophrenia using correlation and regression analyses. The PANSS Cognitive factor showed a small to moderate significant association with MCCB Speed of processing, Working memory, Verbal learning, the Neurocognitive composite score, and the Overall composite score. Notably, however, no relationship was found between the PANSS Negative factor and any of the MCCB scores. The Positive, Excited and Depressed factors also did not show associations with the MCCB. These results highlight the need for refined assessment instruments and support the relative independence of cognition from other domains of psychopathology, including negative symptoms, in patients with schizophrenia.

An FMRI study of the influence of a history of substance abuse on working memory-related brain activation in schizophrenia

There has been little investigation of the effects of past substance abuse (SA) on working memory (WM) impairments in schizophrenia. This study examined the behavioral and neurobiological impact of past SA (6 months or longer abstinence period) on WM in schizophrenia. Thirty-seven schizophrenia patients (17 with past SA and 20 without) and 32 controls (12 with past SA and 20 without) completed two versions of a two-back WM task during fMRI scanning on separate days. Analyses focused on regions whose patterns of activation replicated across both n-back tasks. Schizophrenia patients were significantly less accurate than controls on both n-back tasks. No main effects or interactions with past SA on WM performance were observed. However, several fronto-parietal-thalamic regions showed an interaction between diagnostic group and past SA. These regions were significantly more active in controls with past SA compared to controls without past SA. Schizophrenia patients with or without past SA either showed no significant differences, or patients with past SA showed somewhat less activation compared to patients without past SA during WM. These results suggest robust effects of past SA on WM brain functioning in controls, but less impact of past SA in schizophrenia. This is consistent with previous literature indicating less impaired neurocognition in schizophrenia with SA.

Comorbid substance use disorder in schizophrenia: a selective overview of neurobiological and cognitive underpinnings

Although individuals with schizophrenia show a lifetime prevalence of 50% for suffering from a comorbid substance use disorder, substance abuse usually represents an exclusion criterion for studies on schizophrenia. This implies that surprisingly little is known about a large group of patients who are particularly difficult to treat. The aim of the present work is to provide a brief and non-exhaustive overview of the current knowledgebase about neurobiological and cognitive underpinnings for dual diagnosis schizophrenia patients. Studies published within the last 20 years were considered using computerized search engines. The focus was on nicotine, caffeine, alcohol, cannabis and cocaine being among the most common substances of abuse. All drugs of abuse target dopaminergic, glutamatergic and GABAergic transmission which are also involved in the pathophysiology of schizophrenia. Current literature suggests that neurocognitive function might beless disrupted in substance-abusing compared to non-abusing schizophrenia patients, but in particular the neuroimaging database on this topic is sparse. Detrimental effects on brain structure and function were shown for patients for whom alcohol is the main substance of abuse. It is as yet unclear whether this finding might be an artifact of age differences of patient subgroups with different substance abuse patterns. More research is warranted on the specific neurocognitive underpinnings of schizophrenia patients abusing distinct psychoactive substances. Treatment programs might either benefit from preserved cognitive function as a resource or specifically target cognitive impairment in different subgroups of addicted schizophrenia patients.

Comorbid substance abuse in first-episode schizophrenia: effects on cognition and psychopathology in the EUFEST study

Studies and meta-analyses investigating the influence of substance use disorder (SUD) (substance abuse or dependence) on psychopathology and neurocognitive function in schizophrenia patients have revealed controversial results. Most studies did only have small samples and did not focus exclusively on first-episode schizophrenia patients.

METHOD

In a post-hoc analysis of the European First Episode Schizophrenia Trial (EUFEST) psychopathology and cognitive performances of patients with (FE-SUD, N=119, consisting of N=88 patients with persisting SUD at baseline and N=31 patients with previous SUD) and without SUD (FE-non-SUD, N=204) were compared at baseline and 6 months follow-up. Neurocognitive assessment included the Rey Auditory Verbal Learning Test (RAVLT); Trail Making Tests A and B (TMT), Purdue Pegboard and Digit-Symbol Coding.

RESULTS

In total 31.1% of patients reported SUD, and 22.2% of patients used cannabis. There were no significant differences between patients with and without SUD concerning PANSS scores, extrapyramidal motor symptoms or neurocognitive measures except better performance in psychomotor speed (TMT-A, p=0.033, Cohen's d=0.26) in patients with SUD at 6 months follow-up. Interestingly, SUD patients with ongoing substance use at follow-up showed elevated positive symptoms (PANSS positive score, p=0.008, Cohen's d=0.84) compared to those who abstained. PANSS scores at baseline were increased in patients with an onset of SUD before the age of 16 years. In addition we found a correlation between longer duration of cannabis use and higher cognitive performance as well as reduced symptom improvement and more extrapyramidal motor symptoms in patients with higher frequency of cannabis consumption.

CONCLUSIONS

FE-SUD and FE-non-SUD show similar psychopathology and neuropsychological performances at baseline and during the first 6 months of antipsychotic treatment.

Negative symptoms and executive function in schizophrenia: does their relationship change with illness duration?

BACKGROUND

Negative symptoms and cognitive dysfunction are of crucial functional and prognostic importance in schizophrenia. However, the nature of the relationship between them and the factors that may influence it have not been well established.

AIMS

To investigate whether the relationship between negative symptoms and executive function changes according to the duration of illness in schizophrenia.

METHODS

The Positive and Negative Syndrome Scale was used to assess psychopathology and the Wisconsin Card Sorting Test (WCST) to evaluate executive function in a sample of 200 schizophrenic patients who were classified in 3 groups according to their duration of illness: up to 5 years (short duration group), 6-20 years (intermediate duration group) and over 20 years of illness (long duration group).

RESULTS

Medium-sized correlations were found between negative symptoms and WCST performance as assessed by the number of completed categories in all 3 groups. However, differences were found according to the duration of schizophrenia. For patients in the short duration group, negative symptoms correlated with WCST nonperseverative errors, but for those in the long duration group the correlation was with perseverative errors.

CONCLUSION

We found a differential relationship between negative and cognitive symptoms in different stages of schizophrenia. Illness duration should be considered when studying the relationship between negative symptoms and cognition.

Psychopathologic differences between cannabis-induced psychoses and recent-onset primary psychoses with abuse of cannabis

The study aims to identify psychopathologic variables in cannabis-induced psychosis and recent-onset primary psychoses using the Symptom Checklist-90-R and the Psychiatric Research Interview for Substance and Mental Disorders. A sample of 181 subjects with psychotic symptoms and cannabis use referred to the psychiatry inpatient units of 3 university general hospitals were assessed. The final sample included 50 subjects with a diagnosis of cannabis-induced psychotic disorder (CIPD) and 104 subjects with primary psychotic disorders. Using receiver operating characteristic curves, the most efficient psychopathologic variables for classifying CIPD were interpersonal sensitivity, "depression," phobic anxiety, and Scale to Assess Unawareness of Mental Disorders subscales. The area under the receiver operating characteristic curve of the model including depression and "misattribution" scores was 96.78% (95% confidence interval, 94.43-99.13). Depressive symptoms could be used to distinguish CIPD from other primary psychotic disorders. Clinical variables related to "neurotic" symptoms could be involved in the susceptibility to cannabis-induced psychosis.

Stressing schizotypy: the modulating role of stress-relieving behaviours and intellectual capacity on functional hemispheric asymmetry

Relative cognitive impairments are common along the schizophrenia spectrum reflecting potential psychopathological markers. Yet stress, a vulnerability marker in schizophrenia (including its spectrum), is likewise related to cognitive impairments. We investigated whether one such cognitive marker (attenuated functional hemispheric asymmetry) during stressful life periods might be linked to individuals' schizotypal features or rather to individuals' stress-related experiences and behaviours. A total of 58 students performed a left hemisphere dominant (lateralised lexical decisions) and right hemisphere dominant (sex decisions on composite faces) task. In order to account for individual differences in stress sensitivity we separated participants into groups of high or low cognitive reserve according to their average current marks. In addition, participants filled in questionnaires on schizotypy (short O-LIFE), perceived stress, stress response, and a newly adapted questionnaire that enquired about potential stress compensation behaviour (elevated substance use). The most important finding was that enhanced substance use and cognitive disorganisation contributed to a right and left hemisphere shift in language dominance, respectively. We discuss that (i) former reports on right hemisphere shifts in language dominance with positive schizotypy might be explained by an associated higher substance use and (ii) cognitive disorganisation relates to unstable cognitive functioning that depend on individuals' life circumstances, contributing to published reports on inconsistent laterality-schizotypy relationships.

Different vulnerability indicators for psychosis and their neuropsychological characteristics in the Northern Finland 1986 Birth Cohort

This study is one of very few that has investigated the neuropsychological functioning of both familial and clinical high risk subjects for psychosis. Participants (N = 164) were members of the Northern Finland 1986 Birth Cohort in the following four groups: familial risk for psychosis (n = 62), clinical risk for psychosis (n = 20), psychosis (n = 13), and control subjects (n = 69). The neurocognitive performance of these groups was compared across 19 cognitive variables. The two risk groups did not differ significantly from controls, but differed from the psychosis group in fine motor function. Neuropsychological impairments were not evident in a non-help-seeking high-risk sample.

Effects of acamprosate on cognition in a treatment study of patients with schizophrenia spectrum disorders and comorbid alcohol dependence

Problems with memory and attention are common to both schizophrenia and alcohol dependence. The objectives of this study were to examine the effect of acamprosate treatment on cognition and to assess whether the changes in drinking patterns or psychotic symptoms were related to changes in cognitive functioning. Outpatients with schizophrenia spectrum disorders and alcohol dependence (n = 23) were randomized (double-blind) to either acamprosate or placebo treatment for 12 weeks. Assessments (baseline and week 12) included alcohol use, symptoms of psychosis, memory, and attention. The results showed that acamprosate had no effect on cognitive functioning and that there was no relationship between change in alcohol consumption or psychotic symptoms and change in cognitive functioning in this sample of patients. The finding that acamprosate had no negative effects on cognition is clinically relevant and reinforces previous reports that acamprosate can be used safely for alcohol reduction in this group of patients.