Meta-analysis confirms cannabis use is linked to worse formal thought disorder across the entire psychosis spectrum
Across 19 studies with 5,191 participants, cannabis users showed significantly greater formal thought disorder severity than non-users, regardless of whether they were healthy, had first-episode psychosis, or had schizophrenia.
Quick Facts
What This Study Found
Cannabis users had higher FTD severity overall (SMD 0.21, 95% CI 0.12-0.29, p=0.00009). This held across subgroups: healthy individuals (SMD 0.19, p=0.02), first-episode psychosis (SMD 0.21, p=0.04), and schizophrenia (SMD 0.25, p=0.005). Between-group differences were not significant.
Key Numbers
Studies: 19. Cannabis users: 1,840. Non-users: 3,351. Overall SMD: 0.21 (p=0.00009). Healthy: 0.19 (p=0.02). FEP: 0.21 (p=0.04). Schizophrenia: 0.25 (p=0.005).
How They Did This
Systematic review and meta-analysis searching six databases through July 2022. Included 19 studies with 1,840 cannabis users and 3,351 non-users. Random-effects model. Subgroup analyses by clinical population.
Why This Research Matters
Formal thought disorder (disorganized thinking and speech) is a core psychosis feature. This meta-analysis shows cannabis worsens it across the entire spectrum, from healthy individuals to those with established schizophrenia.
The Bigger Picture
The consistent effect across healthy, FEP, and schizophrenia populations suggests cannabis impacts thought organization through a fundamental mechanism rather than simply worsening pre-existing psychosis.
What This Study Doesn't Tell Us
Mostly cross-sectional studies. Cannot determine causation. FTD measurement varied across studies. Could not assess confounding by other substance use. Moderate heterogeneity.
Questions This Raises
- ?Which dimensions of FTD (poverty of speech, loose associations, tangentiality) are most affected by cannabis?
- ?Does the effect reverse with cannabis cessation?
Trust & Context
- Key Stat:
- Cannabis worsened thought disorder across healthy, FEP, and schizophrenia groups
- Evidence Grade:
- Comprehensive meta-analysis with consistent results across subgroups, though primarily based on cross-sectional data.
- Study Age:
- Published in 2022 with searches through July 2022.
- Original Title:
- Association between formal thought disorder and cannabis use: a systematic review and meta-analysis.
- Published In:
- Schizophrenia (Heidelberg, Germany), 8(1), 78 (2022)
- Authors:
- Argote, Mathilde(4), Sescousse, Guillaume(3), Brunelin, Jérôme(2), Fakra, Eric, Nourredine, Mikail, Rolland, Benjamin
- Database ID:
- RTHC-03680
Evidence Hierarchy
Combines results from multiple studies to find an overall pattern.
What do these levels mean? →Frequently Asked Questions
Does cannabis affect thinking organization?
Yes. This meta-analysis found cannabis users had significantly worse formal thought disorder (disorganized thinking and speech) regardless of whether they were healthy or had a psychotic disorder.
Is the effect only in people with psychosis?
No. The effect was seen in healthy individuals too (SMD 0.19), suggesting cannabis can disorganize thinking even in people without psychotic disorders.
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Cite This Study
https://rethinkthc.com/research/RTHC-03680APA
Argote, Mathilde; Sescousse, Guillaume; Brunelin, Jérôme; Fakra, Eric; Nourredine, Mikail; Rolland, Benjamin. (2022). Association between formal thought disorder and cannabis use: a systematic review and meta-analysis.. Schizophrenia (Heidelberg, Germany), 8(1), 78. https://doi.org/10.1038/s41537-022-00286-0
MLA
Argote, Mathilde, et al. "Association between formal thought disorder and cannabis use: a systematic review and meta-analysis.." Schizophrenia (Heidelberg, 2022. https://doi.org/10.1038/s41537-022-00286-0
RethinkTHC
RethinkTHC Research Database. "Association between formal thought disorder and cannabis use..." RTHC-03680. Retrieved from https://rethinkthc.com/research/argote-2022-association-between-formal-thought
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.