Cannabis-using psychosis patients initially received less severe diagnoses but caught up at second hospitalization
Cannabis users hospitalized for psychosis were initially diagnosed with less severe mental illness at lower rates (20% vs 53%), but by second hospitalization, both groups had similar rates of severe diagnoses around 80%.
Quick Facts
What This Study Found
Researchers reviewed records of 318 patients at their first psychiatric hospitalization for psychotic symptoms, comparing 106 cannabis users (33%) to non-drug users. At first admission, the groups differed dramatically in diagnostic severity: only 20.3% of cannabis users received a severe mental illness diagnosis compared to 53.3% of non-users.
However, this gap disappeared by the second hospitalization. Both groups showed conversion rates of 79-80% from non-severe to severe mental illness diagnoses between first and second admissions. Cannabis users had shorter initial hospitalizations, but their five-year rehospitalization rates were not significantly different from non-users.
The high conversion rate in cannabis users raises two possibilities: either severe mental illness was being under-diagnosed at first admission because clinicians attributed symptoms to cannabis use, or cannabis exposure was actively contributing to the development of more severe illness over time.
Key Numbers
318 patients total, 106 cannabis users (33.3%). Non-users: 53.3% severe mental illness at first admission. Cannabis users: 20.3% severe mental illness at first admission. Both groups: 79-80% conversion to severe mental illness by second admission. Cannabis users had shorter first hospitalization. 5-year rehospitalization rates were similar.
How They Did This
This was a retrospective chart review cohort study at Geha Mental Health Center, Israel, covering admissions between August 2002 and December 2013. A total of 318 patients were included: 106 cannabis users and 212 non-drug users. Demographics, diagnoses, hospitalization duration, and rehospitalization rates were compared. Diagnostic stability between first and second admissions was assessed.
Why This Research Matters
The finding that cannabis users are initially diagnosed less severely but later receive the same diagnoses has major clinical implications. If clinicians are attributing psychotic symptoms to cannabis use and assigning less severe diagnoses as a result, patients may receive inadequate treatment. Alternatively, if cannabis is driving illness progression, this supports early intervention.
The Bigger Picture
This study highlights a critical challenge in psychiatry: disentangling cannabis effects from underlying psychiatric illness at first presentation. The near-identical conversion rates suggest that the initial diagnostic difference may be an artifact of clinical reasoning rather than a true difference in illness severity, raising concerns about systematic under-diagnosis in cannabis-using patients.
What This Study Doesn't Tell Us
Retrospective chart review depends on the quality of medical records. The study was conducted at a single center in Israel. Cannabis use was based on clinical documentation and may be inconsistently recorded. The study could not determine whether cannabis caused illness progression or whether initial diagnoses were simply inaccurate. Only two time points (first and second admission) were analyzed.
Questions This Raises
- ?Are clinicians systematically under-diagnosing severe mental illness in cannabis-using patients?
- ?Does cannabis use accelerate the progression from non-severe to severe psychotic diagnoses?
- ?Should first-episode psychosis treatment be more aggressive in cannabis users given the high conversion rate?
Trust & Context
- Key Stat:
- 79-80% of both groups progressed to severe mental illness diagnoses by second admission
- Evidence Grade:
- This is a retrospective cohort study with a reasonable sample size but limitations inherent to chart review methodology.
- Study Age:
- Published in 2018 with data from 2002-2013.
- Original Title:
- Differences in demographic and clinical characteristics between cannabis users and non-drug users: A retrospective study of patients at first hospitalization due to psychotic symptoms.
- Published In:
- Psychiatry research, 268, 454-459 (2018)
- Authors:
- Balan Moshe, Livia, Weizman, Abraham(7), Ben Dor, David H, Konas, Shai, Fischel, Zvi, Aizenberg, Dov, Gothelf, Doron, Valevski, Avi
- Database ID:
- RTHC-01583
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
Do cannabis users get less severe psychiatric diagnoses?
At first hospitalization, yes. Only 20% of cannabis users received a severe mental illness diagnosis versus 53% of non-users. However, by second admission, both groups had converged to approximately 80% severe diagnoses, suggesting initial under-diagnosis rather than truly milder illness.
Does cannabis cause psychosis to get worse over time?
This study cannot definitively answer that question. The high conversion rate (79-80%) from non-severe to severe diagnoses could reflect either under-diagnosis at first admission or actual illness progression. Both mechanisms may be at work.
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Cite This Study
https://rethinkthc.com/research/RTHC-01583APA
Balan Moshe, Livia; Weizman, Abraham; Ben Dor, David H; Konas, Shai; Fischel, Zvi; Aizenberg, Dov; Gothelf, Doron; Valevski, Avi. (2018). Differences in demographic and clinical characteristics between cannabis users and non-drug users: A retrospective study of patients at first hospitalization due to psychotic symptoms.. Psychiatry research, 268, 454-459. https://doi.org/10.1016/j.psychres.2018.07.037
MLA
Balan Moshe, Livia, et al. "Differences in demographic and clinical characteristics between cannabis users and non-drug users: A retrospective study of patients at first hospitalization due to psychotic symptoms.." Psychiatry research, 2018. https://doi.org/10.1016/j.psychres.2018.07.037
RethinkTHC
RethinkTHC Research Database. "Differences in demographic and clinical characteristics betw..." RTHC-01583. Retrieved from https://rethinkthc.com/research/balan-2018-differences-in-demographic-and
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.