Cannabis-related psychosis hospitalizations in Portugal increased 29-fold from 2000 to 2015
In Portuguese public hospitals, hospitalizations with a primary diagnosis of psychotic disorder and secondary diagnosis of cannabis abuse or dependence rose from 20 per year in 2000 to 588 per year in 2015, a 29-fold increase.
Quick Facts
What This Study Found
Cannabis-related psychotic disorder hospitalizations rose 29.4 times over 15 years. Among all psychosis hospitalizations, those with a cannabis diagnosis increased from 0.87% in 2000 to 10.60% in 2015. Patients were predominantly male (89.8%) with a mean age of about 31 years.
Key Numbers
Hospitalizations rose from 20 (2000) to 588 (2015). Total: 3,233 hospitalizations. Average cost: about 3,500 euros per episode. 89.8% male. Mean age: 30.66 years. Cannabis coding rose from 0.87% to 10.60% of all psychosis hospitalizations.
How They Did This
Retrospective observational study analyzing all hospitalizations in Portuguese public hospitals from 2000 to 2015. Cases were identified by primary diagnosis of psychotic disorder/schizophrenia with secondary diagnosis of cannabis dependence or abuse (ICD-9 codes).
Why This Research Matters
The dramatic increase occurred during a period of changing cannabis consumption patterns in Portugal, including higher potency products and more frequent use, suggesting a dose-response relationship at the population level.
The Bigger Picture
While improved diagnostic coding may partly explain the trend, the authors note that changes in cannabis consumption patterns, including more potent products and higher-dose users, likely contributed to the increase.
What This Study Doesn't Tell Us
Administrative data relies on coding accuracy, and increased awareness of cannabis-psychosis links may have led to more frequent secondary diagnosis coding over time. The study cannot establish causation between cannabis use and psychosis.
Questions This Raises
- ?How much of the increase reflects actual rises in cannabis-related psychosis versus improved diagnostic coding?
- ?Has the trend continued after 2015?
- ?How does Portugal's decriminalization policy factor into these patterns?
Trust & Context
- Key Stat:
- 29-fold increase in cannabis-related psychosis hospitalizations
- Evidence Grade:
- Moderate: nationwide hospital data over 15 years, though limited by diagnostic coding changes over time.
- Study Age:
- Published in 2020 in International Journal of Methods in Psychiatric Research.
- Original Title:
- Psychotic disorders hospitalizations associated with cannabis abuse or dependence: A nationwide big data analysis.
- Published In:
- International journal of methods in psychiatric research, 29(1), e1813 (2020)
- Authors:
- Gonçalves-Pinho, Manuel, Bragança, Miguel(2), Freitas, Alberto
- Database ID:
- RTHC-02577
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
Did more people actually get psychosis from cannabis?
The study cannot definitively answer this. The 29-fold increase may partly reflect better recognition and coding of cannabis-related psychosis by clinicians, rather than a pure increase in cases. However, changing cannabis consumption patterns likely also played a role.
Who was most affected?
Nearly 90% were male, with a mean age around 31 years. The gender and age profile is consistent with the known demographics of both heavy cannabis use and first-episode psychosis.
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Cite This Study
https://rethinkthc.com/research/RTHC-02577APA
Gonçalves-Pinho, Manuel; Bragança, Miguel; Freitas, Alberto. (2020). Psychotic disorders hospitalizations associated with cannabis abuse or dependence: A nationwide big data analysis.. International journal of methods in psychiatric research, 29(1), e1813. https://doi.org/10.1002/mpr.1813
MLA
Gonçalves-Pinho, Manuel, et al. "Psychotic disorders hospitalizations associated with cannabis abuse or dependence: A nationwide big data analysis.." International journal of methods in psychiatric research, 2020. https://doi.org/10.1002/mpr.1813
RethinkTHC
RethinkTHC Research Database. "Psychotic disorders hospitalizations associated with cannabi..." RTHC-02577. Retrieved from https://rethinkthc.com/research/goncalves-pinho-2020-psychotic-disorders-hospitalizations-associated
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.