Cannabis-induced psychosis had the highest relapse rate and shortest time between episodes
Among people with substance-induced psychosis in Sweden, those whose psychosis was cannabis-induced had the highest relapse rate at 25.7% and the shortest time between episodes.
Quick Facts
What This Study Found
Cannabis-induced psychosis carried a 2.42x higher risk of relapse compared to alcohol-induced psychosis. Overall, 20% of people with any substance-induced psychosis relapsed within 2 years, with a median time to relapse of 126 days.
Key Numbers
7,320 people studied. 20% (n=1,463) relapsed. Cannabis-induced: 25.7% relapse, HR 2.42. Multi-substance: 23.8% relapse, HR 1.81. Methamphetamine: 19.7% relapse, HR 1.49. 83.3% relapsed with the same substance type. Median relapse: 126 days.
How They Did This
Population-based register study linking Swedish nationwide data for 7,320 people with first-time substance-induced psychosis between 2006 and 2016, with 2-year follow-up using multivariable Cox models.
Why This Research Matters
Substance-induced psychosis is often treated as a one-time event, but this study shows that one in five people relapse within two years, with cannabis-related cases at particularly high risk. This has implications for follow-up care planning.
The Bigger Picture
As cannabis potency and availability increase globally, understanding the longitudinal trajectory of cannabis-induced psychosis becomes crucial for mental health services planning and resource allocation.
What This Study Doesn't Tell Us
Register-based study cannot capture psychotic episodes not leading to hospitalization. Cannabis potency, frequency of use, and other contextual factors were not available in the registers.
Questions This Raises
- ?What interventions after a first cannabis-induced psychosis episode could reduce the 25.7% relapse rate?
- ?Does cannabis potency influence relapse risk?
Trust & Context
- Key Stat:
- Cannabis-induced psychosis: 25.7% relapse rate, 2.42x risk vs alcohol
- Evidence Grade:
- Large population-based register study covering an entire country over a decade, with multivariable adjustment for confounders. Register data provides comprehensive capture of hospitalizations.
- Study Age:
- Published in 2025, data 2006-2016.
- Original Title:
- Relapse in substance-induced psychosis and associated risk factors. A Nationwide register-linkage study from Sweden.
- Published In:
- Addiction (Abingdon, England), 120(7), 1422-1430 (2025)
- Authors:
- Ellilä, Venla, Taipale, Heidi(4), Tiihonen, Jari(3), Mittendorfer-Rutz, Ellenor, Niemelä, Solja
- Database ID:
- RTHC-06398
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
How likely is a second psychotic episode after cannabis-induced psychosis?
In this Swedish study, 25.7% of people with cannabis-induced psychosis had a relapse within two years, the highest rate among all substance types studied.
Which substance causes the most psychosis relapses?
Cannabis-induced psychosis had the highest relapse rate (25.7%) and the strongest statistical association with relapse (2.42x higher than alcohol), followed by multi-substance use (23.8%) and methamphetamine (19.7%).
Read More on RethinkTHC
- THC-amygdala-anxiety-brain
- anandamide-weed-withdrawal
- cannabinoid-receptors-recovery-time
- cannabis-developing-brain-teenagers
- cant-enjoy-anything-without-weed
- dopamine-recovery-after-quitting-weed
- endocannabinoid-system-explained-simply
- endocannabinoid-system-withdrawal
- nervous-system-weed-withdrawal-fight-flight
- teen-weed-use-under-18-effects-brain
- thc-brain-withdrawal
- thc-prefrontal-cortex-brain-effects
- weed-cortisol-stress-hormones
- weed-memory-loss-recovery
- weed-motivation-amotivational-syndrome
- weed-nervous-system-effects
- weed-reward-system-brain
Cite This Study
https://rethinkthc.com/research/RTHC-06398APA
Ellilä, Venla; Taipale, Heidi; Tiihonen, Jari; Mittendorfer-Rutz, Ellenor; Niemelä, Solja. (2025). Relapse in substance-induced psychosis and associated risk factors. A Nationwide register-linkage study from Sweden.. Addiction (Abingdon, England), 120(7), 1422-1430. https://doi.org/10.1111/add.70014
MLA
Ellilä, Venla, et al. "Relapse in substance-induced psychosis and associated risk factors. A Nationwide register-linkage study from Sweden.." Addiction (Abingdon, 2025. https://doi.org/10.1111/add.70014
RethinkTHC
RethinkTHC Research Database. "Relapse in substance-induced psychosis and associated risk f..." RTHC-06398. Retrieved from https://rethinkthc.com/research/ellila-2025-relapse-in-substanceinduced-psychosis
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.