Post-Legalization Surge and Regional Disparities in Cannabis-Induced Psychiatric Disorders: Multicenter Evidence from Thailand (2021–2024)
S. Joowong, P. Tansupasiri
European Psychiatry June 1, 2026 DOI: 10.1192/j.eurpsy.2026.10873 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Retrospective multicenter observational study Peer reviewed |
|---|---|
| Sample size | 2,131 |
| Population | Patients with cannabis-related psychiatric presentations at five psychiatric hospitals in Thailand between 2021 and 2024 |
| Duration | 2021 to 2024 (4-year period) |
| Topics | Cannabis |
| Key findings | Cannabis-related psychiatric cases in Thailand increased significantly after decriminalization, with an average annual rise of 146.6 cases. Males were more likely to be diagnosed with cannabis-induced psychotic disorders (F1x.5), while females showed higher proportions of schizophrenic spectrum disorders (F2x.xx). Cannabis-use history among F1x.5 patients rose from 62.4% to 78.3% and among F2x.xx patients from 18.7% to 27.5% over the study period. |
Abstract
Introduction: Following Thailand’s cannabis decriminalization in 2022, a marked rise in psychiatric presentations related to cannabis use has been observed nationwide. While international evidence has linked high-THC cannabis exposure to psychosis and substance-induced disorders, empirical data from Asian settings remain limited. This late-breaking study provides updated national trends and regional variations in cannabis-related psychiatric cases following the policy change.
Objectives: To analyze the trend of cannabis-related psychiatric cases in Thailand during the period between pre-policy (2021) and after legalization (2023 and 2024). To examine the association between psychiatric diagnostic codes (F1x.5 and F2x.xx) and cannabis-use history.
Methods: A retrospective multicenter study analyzed data from five psychiatric hospitals representing five major regions of Thailand (North, Northeast, Central, South, and East) between 2021 (pre-policy) and 2024 (post-policy). Demographic and clinical data were extracted from hospital records. Statistical analyses included descriptive statistics, Chi-square tests, and linear regression to assess time trends and gender–diagnosis associations between cannabis- induce psychotic disorders (F1x.5) and schizophrenic spectrum disorders (F2x.xx).
Results: Between 2021–2024, 2,131 cannabis-related psychiatric patients were identified (82.4% male, 17.6% female). Cases increased significantly post-legalization, with an average annual rise of 146.6 cases (β = +146.6, R2 = 0.875). Males were more likely to be diagnosed with F1x.5, while females showed higher proportions of F2x.xx (χ2 = 122.5, p < 0.001). The proportion of patients with cannabis-use history among F1x.5 diagnoses rose from 62.4% (2021) to 78.3% (2024), indicating a significant upward trend (χ2trend = 8.52, p = 0.004),while among F2x.xx patients, it increased from 18.7% to 27.5% during the same period. Regional analysis revealed higher cannabis-related prevalence in northeastern hospitals (up to 48.3%), whereas southern and northern hospitals showed stronger psychotic disorder patterns. Image 1: Image 1: Long description.Line graph showing an upward trend in cannabis-use history for two diagnosis groups from 2021 to 2024. See long description. Image 2: Image 2: Long description.A grouped bar chart comparing cannabis-use history and psychiatric diagnoses across five regions. See long description.
Conclusions: This study provides one of the first multicenter evidences from Thailand demonstrating a post-legalization rise in cannabis-induced psychiatric morbidity. The results call for innovative, regionally tailored, and gender-sensitive strategies within national mental health surveillance systems. Disclosure of Interest None Declared
Comparable studies
Other observational and cohort studies on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population | 2009 | Case-control study | n = 454 |
| Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population | 2013 | Observational study | |
| Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people | 2000 | Observational | |
| Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline | 2011 | Observational cohort | n = 1,923 |
| Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... | 2005 | Observational cohort | n = 535 |