Association between cannabis use frequency and age of onset of psychotic disorders in young adults: A retrospective clinical study
Tobias Karl Breitner, Lena Maria Hoffmann
International Journal of Research in Psychiatry July 1, 2026 DOI: 10.22271/27891623.2026.v6.i2.a.115 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Retrospective clinical study (case record review) Peer reviewed |
|---|---|
| Sample size | 285 |
| Population | Patients aged 16–30 with a primary ICD-10 psychotic disorder diagnosis (F20–F29) attending tertiary psychiatric facilities in Germany |
| Topics | Cannabis |
| Key findings | Heavy or daily cannabis users had an average age of psychosis onset of 19.3 years compared with 26.4 years for non-users, a 7.1-year difference, and longer cannabis use duration correlated with younger onset age. The authors argue that heavy and prolonged cannabis use is strongly associated with earlier onset of psychotic disorders and that this carries implications for preventive psychiatry and forensic policy in Germany. |
Abstract
Background: Cannabis remains the most widely used illicit psychoactive substance in Europe, and Germany's landmark 2024 partial legalisation of recreational cannabis has made the clinical evidence base for cannabis-psychosis associations particularly relevant for German public health and forensic psychiatry policy. A growing body of evidence suggests that heavy cannabis use is associated with an earlier age of first psychotic episode and higher rates of schizophrenia-spectrum diagnoses in genetically predisposed individuals.
Objective: This retrospective clinical study examined the association between cannabis use frequency and the age of onset of psychotic disorders in young adults aged 16–30 attending tertiary psychiatric facilities in Germany.
Methods: Psychiatric case records of 285 patients aged 16–30 with a primary ICD-10 psychotic disorder diagnosis (F20–F29) were retrospectively reviewed. Cannabis use frequency was categorised into four groups. ANOVA and Pearson's correlation quantified associations with age of psychosis onset.
Results: Heavy/daily cannabis users showed the earliest mean age of psychosis onset (19.3 ± 1.4 years) compared to non-users (26.4 ± 2.1 years), a difference of 7.1 years (p < 0.001; Cohen's f = 0.72). Cannabis use duration was negatively correlated with onset age (r = ?0.62, p < 0.001).
Conclusion: Cannabis use, particularly heavy and prolonged use, is strongly associated with significantly earlier onset of psychotic disorders in young German adults. These findings carry urgent implications for preventive psychiatry and forensic policy in the context of Germany's evolving cannabis regulation landscape.
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 |