Cannabis use was modestly linked to suicidal thoughts and unplanned suicide attempts in a large twin study
Among 9,583 Australian twins, all levels of cannabis involvement were associated with suicidal ideation, with the association persisting after accounting for other psychiatric disorders and substances.
Quick Facts
What This Study Found
Researchers analyzed data from 9,583 individuals (58.5% female, aged 27-40) from the Australian Twin Registry, examining relationships between cannabis use levels and suicidal thoughts and behaviors. Cannabis involvement was categorized into four levels: no use, use only, 1-2 disorder symptoms, and 3+ symptoms.
All levels of cannabis involvement were associated with suicidal ideation (odds ratios 1.28-2.00), and these associations persisted after controlling for other psychiatric disorders and substance use. Cannabis involvement was also associated with unplanned (but not planned) suicide attempts.
Twin analyses revealed that shared genetic factors (correlation 0.45) and environmental factors (correlation 0.21) contributed to the overlap between cannabis involvement and suicidal ideation, suggesting the association is partly explained by common underlying vulnerabilities rather than a direct causal link.
Key Numbers
9,583 individuals (58.5% female). All cannabis involvement levels associated with suicidal ideation (ORs 1.28-2.00). Genetic correlation: 0.45. Environmental correlation: 0.21. Cannabis associated with unplanned but not planned attempts.
How They Did This
Cross-sectional analysis of 9,583 twins from the Australian Twin Registry, aged 27-40. The Semi-Structured Assessment of the Genetics of Alcoholism (SSAGA) assessed cannabis involvement at four levels. Multinomial logistic regression and twin genetic analyses examined associations with suicidal ideation and attempts.
Why This Research Matters
Understanding the association between cannabis use and suicidality is important for clinical screening. The finding that shared genetic and environmental factors partially explain the link helps clinicians understand that cannabis use may be a marker of underlying vulnerability rather than a direct cause.
The Bigger Picture
The cannabis-suicidality association exists but is modest and partly explained by shared underlying factors. This nuanced finding helps move beyond simple "cannabis causes suicidality" claims toward a more sophisticated understanding of how substance use and mental health vulnerabilities overlap.
What This Study Doesn't Tell Us
Cross-sectional design cannot determine temporal direction. Australian twin sample may not generalize to other populations. Self-reported data. The association is modest and substantially attenuated when controlling for confounders. Cannot distinguish effects of cannabis from correlated risk factors.
Questions This Raises
- ?Does the association between cannabis and suicidality differ by age of onset?
- ?Could the shared genetic factors be identified and used for screening?
- ?Is the link to unplanned attempts particularly concerning from a prevention standpoint?
Trust & Context
- Key Stat:
- ORs 1.28-2.00 for suicidal ideation across all cannabis use levels
- Evidence Grade:
- Large twin study with genetic analysis controlling for shared vulnerability. Cross-sectional design limits causal inference.
- Study Age:
- Published in 2015 using Australian Twin Registry data.
- Original Title:
- The relationship between cannabis involvement and suicidal thoughts and behaviors.
- Published In:
- Drug and alcohol dependence, 150, 98-104 (2015)
- Authors:
- Delforterie, M J, Lynskey, M T(4), Huizink, A C(3), Creemers, H E, Grant, J D, Few, L R, Glowinski, A L, Statham, D J, Trull, T J, Bucholz, K K, Madden, P A F, Martin, N G, Heath, A C, Agrawal, A
- Database ID:
- RTHC-00943
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis cause suicidal thoughts?
This study found a modest association between cannabis use and suicidal ideation, but twin analyses showed that shared genetic and environmental factors partly explain the link. The relationship is likely not purely causal but reflects overlapping vulnerabilities.
Should cannabis users be screened for suicidality?
The association, while modest, persisted after controlling for other psychiatric conditions. Clinicians may want to screen cannabis users for suicidal ideation, particularly those with escalating use or additional risk factors.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-00943APA
Delforterie, M J; Lynskey, M T; Huizink, A C; Creemers, H E; Grant, J D; Few, L R; Glowinski, A L; Statham, D J; Trull, T J; Bucholz, K K; Madden, P A F; Martin, N G; Heath, A C; Agrawal, A. (2015). The relationship between cannabis involvement and suicidal thoughts and behaviors.. Drug and alcohol dependence, 150, 98-104. https://doi.org/10.1016/j.drugalcdep.2015.02.019
MLA
Delforterie, M J, et al. "The relationship between cannabis involvement and suicidal thoughts and behaviors.." Drug and alcohol dependence, 2015. https://doi.org/10.1016/j.drugalcdep.2015.02.019
RethinkTHC
RethinkTHC Research Database. "The relationship between cannabis involvement and suicidal t..." RTHC-00943. Retrieved from https://rethinkthc.com/research/delforterie-2015-the-relationship-between-cannabis
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.