Association between cannabis use and symptom dimensions in schizophrenia spectrum disorders: an individual participant data meta-analysis on 3053 individuals (2023)

FRANÇAIS :
Des chercheurs de plusieurs pays européens, américains et africains ont réalisé une méta-analyse sur l'association entre la consommation de cannabis et la schizophrénie. Ils ont conclu que les résultats ne permettaient pas de déterminer si le cannabis était nuisible ou bénéfique pour les symptômes de la maladie. Ils ont contacté les auteurs des études pertinentes afin d'extraire des ensembles de données brutes et de réaliser une méta-analyse des données individuelles des participants.
Parmi les 1149 études identifiées, 65 étaient éligibles et 21 ensembles de données ont été partagés, totalisant 3053 cas complets. La consommation de cannabis était associée à une plus grande sévérité des symptômes positifs, à une plus faible sévérité des symptômes négatifs et à une plus grande sévérité de l'excitation. Aucune association n'a été trouvée entre la consommation de cannabis et la désorganisation ou la dépression. Ils ont conclu qu'"aucune relation de cause à effet ne peut être déduite des résultats actuels. Les résultats pourraient être en faveur d'un effet à la fois préjudiciable et bénéfique du cannabis sur les symptômes positifs et négatifs, respectivement". [Bulletin IACM 24/09/2023]
ENGLISH:
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.