In a 6-year follow-up of 161 early psychosis patients, cannabis use at first admission predicted significantly more hospital readmissions and longer total hospital stays, especially in male and Black patients.
Read this if you or someone you know has experienced psychosis and uses cannabis, and wants to understand the long-term implications.
Cannabis predicted more readmissions and 197 total hospital days over 6 years
What the researchers found
Researchers followed 161 patients admitted to an early psychosis intervention unit for 6 years, tracking hospital readmissions and total time spent hospitalized. Cannabis use was extremely common, with 62.4% reporting lifetime use at admission.
Cannabis use significantly predicted both the number of subsequent hospital readmissions and the total length of stay over the following 6 years. This relationship remained significant even after adjusting for use of other substances, indicating that cannabis had an independent effect on psychosis outcomes.
The impact was not evenly distributed across demographics. Male patients who used cannabis had particularly longer hospital stays compared to females. Black patients who used cannabis also had longer stays compared to other ethnic groups. These demographic disparities within the cannabis-using psychosis population highlight additional vulnerability factors.
The average patient had 2.2 readmissions over 6 years, spending a total of 197 days in the hospital, representing an enormous burden on both patients and healthcare systems.
Why it matters
Hospital readmission is one of the most concrete and costly outcomes in psychosis care. This study demonstrates that cannabis use at the first psychosis admission has lasting consequences for the disease trajectory, predicting worse outcomes for years to come. The economic implications are substantial.
The numbers in context
161 early psychosis patients. 62.4% had lifetime cannabis use. Average initial admission: 54.3 days. Over 6 years: 2.2 readmissions on average, 197.4 total hospital days. Cannabis predicted more readmissions and longer stays independent of other substance use. Male and Black patients most affected.
How the study worked
Retrospective cohort study of 161 consecutive early psychosis inpatients. Cannabis use at admission and hospital readmission data (number of readmissions and total length of stay) over a 6-year follow-up were extracted from clinical records. Analyses adjusted for use of other substances.
What this study cannot tell us
The retrospective design limits causal conclusions. Cannabis use was assessed at admission and may not reflect ongoing patterns. Readmission data does not capture outpatient functioning or community care. The study did not account for cannabis type, potency, or frequency. Racial disparities may reflect systemic healthcare factors rather than biological differences.
How to read the evidence
This is a retrospective cohort with 6-year follow-up, providing moderate evidence for the long-term impact of cannabis on psychosis outcomes.
When this study was published
Published in 2018. Cannabis intervention in early psychosis programs continues to be studied.
The bigger picture
This study adds longitudinal evidence to the cannabis-psychosis literature, showing that the association extends well beyond the acute episode. The 6-year follow-up captures the chronic course of illness and demonstrates that cannabis use at the beginning of psychotic illness portends a more difficult trajectory.
Questions still open
- Would cannabis cessation programs integrated into early psychosis intervention reduce readmission rates? Do the racial disparities reflect differences in cannabis use patterns, access to community support, or systemic healthcare inequities? Is cannabis a cause of worse outcomes or a marker of other risk factors?
Common questions
Does cannabis use lead to more psychiatric hospitalizations?
Does it matter who uses cannabis with psychosis?
Read the original research
Longitudinal assessment of the effect of cannabis use on hospital readmission rates in early psychosis: A 6-year follow-up in an inpatient cohort.
Psychiatry research, 268, 381-387
Citation
Colizzi, Marco; Burnett, Natoy; Costa, Rosalia; De Agostini, Mattia; Griffin, James; Bhattacharyya, Sagnik. (2018). Longitudinal assessment of the effect of cannabis use on hospital readmission rates in early psychosis: A 6-year follow-up in an inpatient cohort.. Psychiatry research, 268, 381-387. https://doi.org/10.1016/j.psychres.2018.08.005
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