Cannabis Was Not an Independent Suicide Risk Factor in Psychosis After Accounting for Depression
Among 1,790 Australians with psychotic disorders, daily cannabis use was initially linked to higher suicide attempt rates, but this association disappeared after controlling for depression, loneliness, homelessness, and hallucinations.
Quick Facts
What This Study Found
In unadjusted analyses, daily cannabis users of both sexes had significantly increased odds of suicide attempts. After adjusting for depression, loneliness, homelessness, and hallucinations, the association was no longer significant. Depression was the strongest predictor for both sexes. Post hoc analysis found daily cannabis use may increase risk in older men specifically.
Key Numbers
1,790 participants total. 168 (9.4%) attempted suicide in the past year. Daily cannabis users had elevated risk in unadjusted analysis, but not after adjustment. Depression was the strongest predictor for both sexes.
How They Did This
Analysis of data from 1,065 men and 725 women in the Australian national survey of psychosis. Separate models for each sex examined the impact of daily, casual, or no past-year cannabis use on past-year suicide attempts.
Why This Research Matters
While cannabis is often assumed to increase suicide risk in psychosis, this study shows the apparent association is largely explained by depression and social adversity. This redirects clinical attention to treating depression and addressing social factors rather than focusing solely on cannabis use.
The Bigger Picture
The relationship between cannabis, psychosis, and suicide is more nuanced than often presented. Cannabis users with psychosis may be at higher suicide risk because of associated factors (depression, social isolation) rather than cannabis use itself.
What This Study Doesn't Tell Us
Cross-sectional design cannot determine causation. Self-reported cannabis use and suicide attempts. Cannot fully separate the effects of cannabis from its correlates. Post hoc subgroup finding (older men) needs replication.
Questions This Raises
- ?Does cannabis contribute to the development of depression and social isolation in psychosis patients, creating an indirect pathway to suicide?
- ?Why might older men be specifically vulnerable?
- ?Would treating depression reduce the cannabis-suicide association entirely?
Trust & Context
- Key Stat:
- Depression was the strongest predictor of suicide attempts for both sexes; the cannabis association disappeared after controlling for depression and social factors.
- Evidence Grade:
- Moderate - large national survey with sex-stratified analysis and appropriate confounding adjustment.
- Study Age:
- Published in 2018.
- Original Title:
- Is cannabis a risk factor for suicide attempts in men and women with psychotic illness?
- Published In:
- Psychopharmacology, 235(8), 2275-2285 (2018)
- Database ID:
- RTHC-01873
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis increase suicide risk in people with psychosis?
Not directly, according to this study. While daily cannabis users initially appeared at higher risk, this association was fully explained by depression, loneliness, homelessness, and hallucinations. These co-occurring factors, rather than cannabis itself, appear to drive the elevated risk.
What is the biggest suicide risk factor in psychosis?
Depression was the strongest predictor of suicide attempts for both men and women with psychotic disorders in this study of 1,790 Australians. Social factors like loneliness and homelessness were also significant contributors.
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Cite This Study
https://rethinkthc.com/research/RTHC-01873APA
Waterreus, A; Di Prinzio, P; Badcock, J C; Martin-Iverson, M; Jablensky, A; Morgan, V A. (2018). Is cannabis a risk factor for suicide attempts in men and women with psychotic illness?. Psychopharmacology, 235(8), 2275-2285. https://doi.org/10.1007/s00213-018-4924-6
MLA
Waterreus, A, et al. "Is cannabis a risk factor for suicide attempts in men and women with psychotic illness?." Psychopharmacology, 2018. https://doi.org/10.1007/s00213-018-4924-6
RethinkTHC
RethinkTHC Research Database. "Is cannabis a risk factor for suicide attempts in men and wo..." RTHC-01873. Retrieved from https://rethinkthc.com/research/waterreus-2018-is-cannabis-a-risk
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.