Cannabis-induced psychosis improved rapidly with antipsychotics, but 7% later developed schizophrenia | Research

The takeaway

Among 317 Thai patients hospitalized for cannabis-induced psychosis, symptoms improved significantly within 3 weeks of antipsychotic treatment, but 7% were diagnosed with schizophrenia at 1.3-year follow-up.

People interested in cannabis-induced psychosis, its treatment, and the risk of progression to chronic psychotic illness.

7% progressed to schizophrenia within 1.3 years

What the researchers found

All patients presented with psychosis; 64% had mood symptoms and 61% sleep problems. Risperidone was the most prescribed antipsychotic (83.6%) at a mean dose of 8 mg/day. BPRS scores improved significantly by day 22 (p<0.001). Average hospital stay was 28 days. At 1.3-year follow-up, 7% were diagnosed with schizophrenia.

Why it matters

This is one of the larger studies on cannabis-induced psychosis treatment outcomes. The finding that 7% progressed to schizophrenia at follow-up supports the concept that CIP can be a gateway to persistent psychotic illness in a subset of patients.

The numbers in context

317 patients analyzed (mostly male, mean age 21). 98.7% received antipsychotics. Risperidone prescribed in 83.6% at mean 8 mg/day. 34.5% also received benzodiazepines. BPRS baseline: 55.2. Average LOS: 28 days. 7% diagnosed with schizophrenia at 1.3-year follow-up.

How the study worked

Retrospective chart review at the Princess Mother National Institute on Drug Abuse Treatment, Thailand. 317 patients meeting ICD-10 criteria for cannabis-induced psychosis with positive urine THC, admitted October 2013 to September 2019. BPRS scores tracked weekly.

What this study cannot tell us

Retrospective design with no control group. Thai population and smoked cannabis only may limit generalizability. Short follow-up (1.3 years) may underestimate eventual schizophrenia diagnoses. No information on cannabis cessation after discharge.

How to read the evidence

Large retrospective cohort with standardized symptom measurement. Limited by lack of control group, short follow-up, and single-country design.

When this study was published

Published in 2024 with data from 2013-2019 in Thailand.

The bigger picture

The transition from cannabis-induced psychosis to schizophrenia is a critical clinical concern. The 7% conversion rate at 1.3 years adds to evidence that CIP is not always self-limiting, reinforcing the importance of follow-up monitoring after an initial psychotic episode.

Questions still open

What predicts which CIP patients will develop schizophrenia? Does cannabis cessation after a psychotic episode prevent progression? Would longer follow-up reveal higher conversion rates?

Common questions

Can cannabis cause permanent psychosis?

In this study, most patients with cannabis-induced psychosis recovered with treatment, but 7% were diagnosed with schizophrenia within about a year. This suggests that for a small subset, a psychotic episode triggered by cannabis may mark the beginning of a chronic condition.

How is cannabis psychosis treated?

Antipsychotic medication was the mainstay of treatment, with risperidone used most often (83.6% of patients). Most patients also received benzodiazepines and/or antidepressants for associated symptoms. Symptoms improved significantly within about 3 weeks.

Read the original research

Real world clinical outcomes of treatment of cannabis-induced psychosis and prevalence of cannabis-related primary psychosis: a retrospective study.

BMC psychiatry, 24(1), 626

View on PubMed ↗Publisher’s paper ↗

Citation

Chuenchom, Onrumpha; Suansanae, Thanarat; Lukanapichonchut, Lumsum; Suwanmajo, Somporn; Suthisisang, Chuthamanee. (2024). Real world clinical outcomes of treatment of cannabis-induced psychosis and prevalence of cannabis-related primary psychosis: a retrospective study.. BMC psychiatry, 24(1), 626. https://doi.org/10.1186/s12888-024-06075-6