Skip to main content Accessibility help

Trends in cannabis use prior to first presentation with schizophrenia, in South-East London between 1965 and 1999

  • J. BOYDELL (a1), J. VAN OS (a1), A. CASPI (a1), N. KENNEDY (a1), E. GIOUROUKOU (a1), P. FEARON (a1), M. FARRELL (a1) and R. M. MURRAY (a1)...


Background. There is evidence that cannabis use might be relevant to the aetiology of schizophrenia. We aimed to measure any change in cannabis use over time in those first presenting with schizophrenia in South-East London from 1965 to 1999, and compare this with change in use in those presenting with non-psychotic psychiatric disorders.

Method. The rate of cannabis use in the year prior to first ever presentation was measured over seven time periods. Logistic regression modelling was used to determine (a) whether cannabis use changed over time, after controlling for age, sex and ethnicity, and (b) whether there was an interaction between diagnosis and time.

Results. Cannabis use increased over time in both the schizophrenia group [odds ratio per time period (OR) 2·03, 95% confidence interval (CI) 1·74–2·38, p<0·0001] and the non-psychotic disorders group (OR 1·24, 95% CI 1·05–1·47, p=0·012), after controlling for age, sex and ethnicity. However, the effect of time was significantly greater in the schizophrenia group than in the non-schizophrenia group (χ2=17, p<0·0001).

Conclusion. Cannabis use in the year prior to presentation with schizophrenia increased markedly between 1965 and 1999, and disproportionately so compared to increase in cannabis use in other psychiatric disorders.


Corresponding author

Division of Psychological Medicine, PO Box 63, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, UK. (Email:
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Psychological Medicine
  • ISSN: 0033-2917
  • EISSN: 1469-8978
  • URL: /core/journals/psychological-medicine
Please enter your name
Please enter a valid email address
Who would you like to send this to? *


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed