A systematic review of 22 studies found daily high-potency cannabis use was associated with 3-fold higher dissociation odds in first-episode psychosis patients, though symptoms were largely reversible with cessation.
Psychiatrists treating first-episode psychosis, cannabis-using individuals with psychotic symptoms, mental health researchers.
3.21x dissociation odds with daily high-potency use
What the researchers found
Among 3,847 participants across 22 studies, daily high-potency cannabis use was associated with 3.21-fold increased odds of clinically significant dissociation (95% CI 2.14-4.82) and more severe anomalous self-experiences. Cannabis users showed DES-II score elevations of 11-13 points exceeding clinical thresholds. Cannabis-related dissociation showed distinct features including self-world boundary confusion. Approximately 75% showed dissociation reduction following cannabis cessation.
Why it matters
This review reveals that cannabis does not just trigger psychotic symptoms but fundamentally disturbs the sense of self in first-episode psychosis patients. The dissociative effects, including feeling disconnected from reality and confusion about self-boundaries, may explain why cannabis-using psychosis patients have worse outcomes. The reversibility finding offers hope.
The numbers in context
22 studies, 3,847 participants. Daily high-potency use: OR 3.21 for dissociation. DES-II elevations: 11-13 points. ~75% showed improvement after cessation. Worse functional outcomes: GAF 52 vs 67 in non-users (p<0.001).
How the study worked
Systematic review following PRISMA guidelines, searching four databases (PubMed, Scopus, PsycINFO, Web of Science) from January 1990 to September 2025. 22 studies meeting inclusion criteria with total N=3,847. GRADE certainty assessed as moderate for dissociative symptoms.
What this study cannot tell us
Most studies were observational. Cannot fully establish causation. GRADE certainty was low for self-disturbance outcomes due to limited direct evidence. Heterogeneous assessment tools across studies. Cannot determine pre-existing dissociative tendencies.
How to read the evidence
Moderate: systematic review with GRADE assessment, moderate certainty for dissociative outcomes, limited self-disturbance data.
When this study was published
2025 study
The bigger picture
Understanding that cannabis disrupts fundamental self-experience, not just causing hallucinations or delusions, changes how clinicians should approach cannabis-using psychosis patients. The finding that most patients improve with cessation provides a concrete, evidence-based reason to prioritize cannabis cessation in treatment.
Questions still open
- Does cannabis-induced dissociation represent a distinct psychosis subtype requiring different treatment? Would the 25% who do not improve with cessation benefit from targeted dissociation-focused therapy? Are there genetic factors predicting cannabis-related dissociation?
Common questions
Does cannabis cause a different kind of psychosis?
Do the effects reverse if you stop using cannabis?
Read the original research
Self-disturbance in first-episode psychosis: Theoretical framework and potential cannabis interactions - a systematic review.
Frontiers in psychiatry, 16, 1733254
Citation
Ricci, Valerio; De Berardis, Domenico; Martinotti, Giovanni; Maina, Giuseppe. (2025). Self-disturbance in first-episode psychosis: Theoretical framework and potential cannabis interactions - a systematic review.. Frontiers in psychiatry, 16, 1733254. https://doi.org/10.3389/fpsyt.2025.1733254
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