Psychological Medicine

Original Articles

Cannabis use and psychosis: re-visiting the role of childhood trauma

J. E. Houstona1 c1, J. Murphya2, M. Shevlina2 and G. Adamsona2

a1 Division of Psychology, Nottingham Trent University, Nottingham, UK

a2 School of Psychology, University of Ulster, Magee, Londonderry, UK

Abstract

Background Cannabis consumption continues to be identified as a causal agent in the onset and development of psychosis. However, recent findings have shown that the effect of cannabis on psychosis may be moderated by childhood traumatic experiences.

Method Using hierarchical multivariate logistic analyses the current study examined both the independent effect of cannabis consumption on psychosis diagnosis and the combined effect of cannabis consumption and childhood sexual abuse on psychosis diagnosis using data from the Adult Psychiatric Morbidity Survey 2007 (n=7403).

Results Findings suggested that cannabis consumption was predictive of psychosis diagnosis in a bivariate model; however, when estimated within a multivariate model that included childhood sexual abuse, the effect of cannabis use was attenuated and was not statistically significant. The multivariate analysis revealed that those who had experienced non-consensual sex in childhood were over six times [odds ratio (OR) 6.10] more likely to have had a diagnosis of psychosis compared with those who had not experienced this trauma. There was also a significant interaction. Individuals with a history of non-consensual sexual experience and cannabis consumption were over seven times more likely (OR 7.84) to have been diagnosed with psychosis compared with those without these experiences; however, this finding must be interpreted with caution as it emerged within an overall analytical step which was non-significant.

Conclusions Future studies examining the effect of cannabis consumption on psychosis should adjust analyses for childhood trauma. Childhood trauma may advance existing gene–environment conceptualisations of the cannabis–psychosis link.

(Received July 21 2010)

(Revised February 16 2011)

(Accepted March 14 2011)

(Online publication April 18 2011)

Correspondence

c1 Address for correspondence: J. E. Houston, Ph.D., Division of Psychology, Nottingham Trent University, Burton Street, Nottingham NG1 4BU, UK. (Email: james.houston@ntu.ac.uk)

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