Is cannabis a risk factor for suicide attempts in men and women with psychotic illness?
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To investigate whether recent cannabis use by men and women with psychotic disorders was associated with increased risk of suicide attempt, and to determine associated factors, stratified by sex.
Data from 1065 men and 725 women interviewed in the Australian national survey of psychosis were analysed to model separately, for each sex, the impact of daily, casual or no past-year cannabis use and other risk factors including age, on a past-year suicide attempt.
In the past year, 168 (9.4%) participants attempted suicide. Unadjusted analyses showed daily cannabis users of both sexes had significantly increased odds of attempting suicide compared to non-users. After adjusting for confounding factors, this relationship was no longer significant. Depression had the strongest association with attempting suicide for both sexes. Sex differences in other risk factors were observed. In post hoc analysis, daily cannabis use was associated with higher odds of attempting suicide in older men compared to non-users; this was not found in younger men or women.
Associations between past-year cannabis use and suicide attempts were confounded by other factors (depression, loneliness, homelessness and hallucinations). The possibility of greater risk of suicidal behaviour with regular cannabis use for older men should be considered.
KeywordsSuicide attempt Risk factors Cannabis Sex Psychotic disorders Age
This publication is based on data collected in the framework of the 2010 Australian National Survey of High Impact Psychosis. The members of the Survey of High Impact Psychosis Study Group at the time of the survey were V Morgan (Project Director); A Jablensky (Chief Scientific Advisor); A Waterreus (Project Coordinator); A Mackinnon (Statistician); R Bush, D Castle, M Cohen, C Galletly, C Harvey, P. McGorry, J McGrath, H Stain (Site Directors); V Carr (Australian Schizophrenia Research Bank); A Neil (Health Economics); B Hocking (SANE Australia); and S Saw (Australian Government Department of Health and Ageing). This report acknowledges, with thanks, the hundreds of mental health professionals who participated in the preparation and conduct of the survey and the many Australians with psychotic disorders who gave their time and whose responses form the basis of this publication.
This study was supported by the Australian Government Department of Health and Ageing. JCB is funded by the Cooperative Research Centre-Mental Health, Carlton, Victoria.
Compliance with ethical standards
The Institutional Human Research Ethics Committees at all sites approved the study. All authors have approved the final article.
Conflict of interest
The authors declare that they have no conflicts of interest.
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