Association of cannabis use with hospital admission and treatment resistance in people with first episode psychosis in South London

Rashmi Patel, Robin Wilson, Richard Jackson, Michael Ball, Hitesh Shetty, Matthew Broadbent, Robert Stewart, Philip McGuire, Sagnik Bhattacharyya

Research output: Contribution to journalMeeting abstractpeer-review

60 Citations (Scopus)


Background: Cannabis is frequently used among individuals with first episode psychosis (FEP) and its components (including tetrahydrocannabinoland cannabidiol) have been implicated in the underlying pathophysiology as well as potential therapies. However, these findings are often based on selected samples which may not be representative of a ‘real-world’ clinical population. We sought to investigate how cannabis was associated with treatment response in a large clinical dataset of people with FEP.

Method: Data were obtained from anonymized electronic health records of 2026 people with FEP in South London. Cannabis use documented within one month of presentation was identified using natural language processing. Data on subsequent hospital admission, clozapine prescription and the number of unique antipsychotics prescribed up to 5 years following presentation were obtained. Their relationship with cannabis use was analysed using multivariable logistic and Poisson regression with age, gender, ethnicity, marital status and diagnosis as covariates.

Results: 939 (46.3%) used cannabis at first presentation. Cannabis use was most strongly associated among those who were aged between 16 and 25 years, male and single and associated with hospital admission (OR 1.61, 95% CI 1.21–2.15) and increased number of unique antipsychotics (IRR 1.13, 95% CI 1.03–1.22). 15.8% of patients using cannabis had been prescribed clozapine compared to 12.0% not using cannabis.

Conclusion: Cannabis use was associated with increased likelihood of hospital admission and treatment resistance following presentation with psychosis. These findings highlight a need for further research into the impact of cannabis use on treatment response in people with psychosis.
Original languageEnglish
Pages (from-to)59-59
Number of pages1
JournalEarly Intervention in Psychiatry
Issue numberS1
Publication statusPublished - 11 Nov 2014


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