The relationship between cannabis use and cognition in people diagnosed with first-episode psychosis

Adolescent cannabinoid exposure rescues phencyclidine-induced social deficits through modulation of CA2 transmission

Psychotic disorders entail intricate conditions marked by disruptions in cognition, perception, emotions, and social behavior. Notably, psychotic patients who use cannabis tend to show less severe deficits in social behaviors, such as the misinterpretation of social cues and the inability to interact with others. However, the biological underpinnings of this epidemiological interaction remain unclear. Here, we used the NMDA receptor blocker phencyclidine (PCP) to induce psychotic-like states and to study the impact of adolescent cannabinoid exposure on social behavior deficits and synaptic transmission changes in hippocampal area CA2, a region known to be active during social interactions. In particular, adolescent mice underwent 7 days of subchronic treatment with the synthetic cannabinoid, WIN 55, 212-2 (WIN) followed by one injection of PCP. Using behavioral, biochemical, and electrophysiological approaches, we showed that PCP persistently reduced sociability, decreased GAD67 expression in the hippocampus, and induced GABAergic deficits in proximal inputs from CA3 and distal inputs from the entorhinal cortex (EC) to CA2. Notably, WIN exposure during adolescence specifically restores adult sociability deficits, the expression changes in GAD67, and the GABAergic impairments in the EC-CA2 circuit, but not in the CA3-CA2 circuit. Using a chemogenetic approach to target EC-CA2 projections, we demonstrated the involvement of this specific circuit on sociability deficits. Indeed, enhancing EC-CA2 transmission was sufficient to induce sociability deficits in vehicle-treated mice, but not in animals treated with WIN during adolescence, suggesting a mechanism by which adolescent cannabinoid exposure rescues sociability deficits caused by enhanced EC-CA2 activity in adult mice.

Does cannabis affect cognitive functioning in patients with schizophrenia?

Introduction

Cannabis use impairs cognitive performance in healthy subjects; several studies have shown improved cognitive outcomes in schizophrenic patients using cannabis. The aim of this study was to evaluate the effects of cannabis use on cognitive function in Moroccan patients with schizophrenia who were cannabis users.

Method

Two groups were recruited in a Moroccan University Psychiatric Centre. Fifty patients diagnosed with schizophrenia according to the DSM-V who were cannabis users (SZ CANN +) and forty-nine patients diagnosed with schizophrenia according to DSM-V who do not use cannabis (SZ CANN-). Cognitive functioning was assessed using the CogState neuropsychological battery.

Results

The results of the study suggest that SZ CANN- patients performed better in the test of psychomotor function, attention and verbal memory. While SZ CANN+ patients performed better in the test of working memory, visual memory and emotional recognition. We found no relationship between SZ CANN+ patients and SZ CANN- patients concerning executive function.

Conclusions

Our results suggest that cannabis use may have different effects on neurocognitive functioning. It is associated with disorders of psychomotor function, attention and verbal memory. So, it is associated with an improvement in working memory, visual memory and emotion recognition.

Cannabis and Psychosis

Psychosis and cannabis use may overlap in multiple ways in young people. Research suggests that cannabis use increases risk for having psychotic symptoms, both attenuated (subthreshold) and acute. Cannabis use may also exacerbate psychosis symptoms among young people with underlying psychosis risk and psychotic disorders. Although there are suggestions for treating co-occurring psychosis and cannabis use in young people (e.g., incorporating cannabis use assessment and treatment strategies into specialized early psychosis care), there are many gaps in clinical trial research to support evidence-based treatment of these overlapping concerns.

Association between cannabis use and symptom dimensions in schizophrenia spectrum disorders: an individual participant data meta-analysis on 3053 individuals

Background

The association between cannabis use and positive symptoms in schizophrenia spectrum disorders is well documented, especially via meta-analyses. Yet, findings are inconsistent regarding negative symptoms, while other dimensions such as disorganization, depression, and excitement, have not been investigated. In addition, meta-analyses use aggregated data discarding important confounding variables which is a source of bias.

Methods

PubMed, ScienceDirect and PsycINFO were used to search for publications from inception to September 27, 2022. We contacted the authors of relevant studies to extract raw datasets and perform an Individual Participant Data meta-analysis (IPDMA). Inclusion criteria were: psychopathology of individuals with schizophrenia spectrum disorders assessed by the Positive and Negative Syndrome Scale (PANSS); cannabis-users had to either have a diagnosis of cannabis use disorder or use cannabis at least twice a week. The main outcomes were the PANSS subscores extracted via the 3-factor (positive, negative and general) and 5-factor (positive, negative, disorganization, depression, excitement) structures. Preregistration is accessible via Prospero: ID CRD42022329172.

Findings

Among the 1149 identified studies, 65 were eligible and 21 datasets were shared, totaling 3677 IPD and 3053 complete cases. The adjusted multivariate analysis revealed that relative to non-use, cannabis use was associated with higher severity of positive dimension (3-factor: Adjusted Mean Difference, aMD = 0.34, 95% Confidence Interval, CI = [0.03; 0.66]; 5-factor: aMD = 0.38, 95% CI = [0.08; 0.63]), lower severity of negative dimension (3-factor: aMD = -0.49, 95% CI [-0.90; -0.09]; 5-factor: aMD = -0.50, 95% CI = [-0.91; -0.08]), higher severity of excitement dimension (aMD = 0.16, 95% CI = [0.03; 0.28]). No association was found between cannabis use and disorganization (aMD = -0.13, 95% CI = [-0.42; 0.17]) or depression (aMD = -0.14, 95% CI = [-0.34; 0.06]).

Interpretation

No causal relationship can be inferred from the current results. The findings could be in favor of both a detrimental and beneficial effect of cannabis on positive and negative symptoms, respectively. Longitudinal designs are needed to understand the role of cannabis is this association. The reported effect sizes are small and CIs are wide, the interpretation of findings should be taken with caution.

Funding

This research did not receive any specific grant or funding. Primary financial support for authors was provided by Le Vinatier Psychiatric Hospital.

Cannabis and Psychosis

Psychosis and cannabis use may overlap in multiple ways in young people. Research suggests that cannabis use increases risk for having psychotic symptoms, both attenuated (subthreshold) and acute. Cannabis use may also exacerbate psychosis symptoms among young people with underlying psychosis risk and psychotic disorders. Although there are suggestions for treating co-occurring psychosis and cannabis use in young people (e.g., incorporating cannabis use assessment and treatment strategies into specialized early psychosis care), there are many gaps in clinical trial research to support evidence-based treatment of these overlapping concerns.

The Potential Paradoxical Neurocognitive Effects of Cannabis Use in Patients with Psychotic Disorders: A Critical Meta-Review of Meta-Analytical Evidence

Background: The association between cannabis and cognitive functions has been thoroughly studied in psychotic disorders, but conflictual/paradoxical results have emerged. This critical meta-review examined the magnitude of effects of cannabis on neurocognitive functions in patients with psychotic disorders provided by meta-analyses and evaluated the quality of evidence. Methods: A systematic search of meta-analyses was performed in PubMed, PsycINFO, Web of Science, and Google Scholar. Results: The search retrieved six meta-analyses. Quality of evidence varied from very low to moderate quality. No neurocognitive difference was observed between cannabis users and nonusers in first episode of psychosis samples. Limited evidence showed no significant difference in language, psychomotor functioning, and verbal/visual learning/memory, apart from improvements in verbal and visual memory (recognition). Findings showed better neurocognitive performances in cannabis-using patients for planning/reasoning and working memory. There were tendencies toward significance for processing speed and attention. Most effect sizes showed small to moderate degrees of outperformances in cannabis users. Individuals with lifetime use appeared to show better neurocognitive functions. Conclusion: Evidence indicated nonuniform effects of cannabis use across cognitive domains, with some areas suggesting better cognitive performances in cannabis users, entitled the paradoxical effect of the dually diagnosed. Clinical significance of these findings should be interpreted cautiously.

Longitudinal effects of cannabis use on attentional processes in patients with first episode of psychosis

BACKGROUND

Attention deficits have been considered to be a central characteristic of schizophrenia-spectrum disorders. However, the specific interactions with, and longitudinal effects of, cannabis use at the different stages of the disorder remain unknown. Due to the high percentage of patients who are cannabis users at the onset of the disease, our objective was to explore this relationship and how it evolves in the first three years of the disease.

METHOD

A total of 461 patients with a first episode of psychosis (FEP) and 187 healthy controls were studied. The differences between cannabis users and non-users at baseline were explored based on both sociodemographic variables and performance in neuropsychological tests of attention. The interaction between cannabis, attentional, and clinical variables was followed up at 3 years.

RESULTS

Of the 648 participants included in this study, 229 (35.34%) were cannabis users. Of them, 187 (40.6%) were patients and 42 (22.5%) were healthy controls. At baseline, control groups [cannabis users (N = 42); non-users (N = 145)] outperformed the patient groups [cannabis users (N = 187); non-users (N = 274)] in all attention tasks. Longitudinal analyses showed significant improvements in the attentional domains at 3-year follow-up, mainly in the group of patients who had never used cannabis (N = 238), followed by ex-users (N = 105), and persistent users (N = 43). At 3-year follow-up, the group of ex-users was the one that achieved scores closer to those of healthy controls.

CONCLUSION

FEP patients, both cannabis users and non-users, showed attention deficits. However, the patients who had never used cannabis fared better than cannabis users.

The relationships between cognitive reserve, cognitive functioning and quality of life in first-episode schizophrenia spectrum disorders

Cognitive reserve (CR) has been conceptualized as an individual's ability to optimize or maximize performance through differential recruitment of brain networks. As such, CR may contribute to the heterogeneity of cognitive deficits observed in schizophrenia. This study aimed to assess the relationships between CR, cognition and quality of life in first-episode (FES) patients. A total of 137 patients with either ICD-10 schizophrenia or "acute and transient psychotic disorders" diagnosis, and 62 healthy controls had completed a comprehensive assessment of six cognitive domains: speed of processing, attention, working memory/flexibility, verbal memory, visual memory, and abstraction/executive functioning. CR was calculated from the participants' education, premorbid IQ, and socioeconomic status. The results suggested that in patients, CR was positively related to cognitive performance in all domains, explaining 42.6% of the variance observed in cognition overall. Effects of CR in the control group were limited to three domains: speed of processing, abstraction/executive function and working memory/flexibility. These results suggest that CR largely contributes to cognitive variations present in FES patients. In addition, CR was negatively related to the social construct of patients' quality of life, and positively to symptom severity and general functioning.