Large Australian study: cannabis use during adolescence independently predicted self-harm
In a cohort of 1,943 adolescents followed to age 29, cannabis use during adolescence was independently associated with a 2.4-fold increased risk of self-harm, alongside depression, anxiety, and alcohol use.
Quick Facts
What This Study Found
A population-based cohort of 1,943 Australian adolescents was followed from age 15.9 to 29 with seven waves of assessment. Self-harm was reported by 8% during adolescence, with higher rates in girls (10%) than boys (6%).
During adolescence, incident self-harm was independently associated with depression and anxiety symptoms (HR 3.7), cannabis use (HR 2.4), high-risk alcohol use (HR 2.1), antisocial behavior (HR 1.9), and cigarette smoking (HR 1.8). Cannabis use remained a significant predictor after adjusting for all other risk factors.
Most self-harming behavior resolved spontaneously during the transition to adulthood. Adolescent depression and anxiety was the strongest predictor of continuing self-harm into young adulthood (HR 5.9).
Key Numbers
1,943 adolescents, 7 waves, mean ages 15.9-29.0. Self-harm prevalence: 8% in adolescence. Cannabis HR: 2.4 (95% CI 1.4-4.4). Depression/anxiety: HR 3.7. Alcohol: HR 2.1. Most self-harm resolved spontaneously.
How They Did This
Population-based stratified random sample of 1,943 adolescents from 44 schools in Victoria, Australia. Seven waves of questionnaires and telephone interviews from mean age 15.9 to 29.0 years (1992-2008). Cox regression for risk factor identification.
Why This Research Matters
Cannabis was identified as an independent risk factor for self-harm, separate from depression, anxiety, and other substance use. This has implications for suicide prevention: addressing cannabis use in at-risk adolescents may be an underappreciated component of self-harm prevention.
The Bigger Picture
Published in The Lancet, this study was influential in establishing cannabis use as a modifiable risk factor for self-harm. The finding that most self-harm resolves spontaneously but depression predicts persistence informed clinical prioritization.
What This Study Doesn't Tell Us
Self-reported cannabis use and self-harm. Association does not prove causation. Confounding by personality traits, trauma, or other unmeasured factors is possible. Australian sample may not generalize globally.
Questions This Raises
- ?Would cannabis cessation reduce self-harm risk in at-risk adolescents?
- ?Does cannabis cause self-harm or does an underlying factor drive both?
- ?Should cannabis screening be part of suicide risk assessment?
Trust & Context
- Key Stat:
- 2.4x increased self-harm risk associated with adolescent cannabis use
- Evidence Grade:
- Large population-based cohort published in The Lancet with long follow-up and multiple adjustment. Strong evidence for association, though causation cannot be definitively established.
- Study Age:
- Published in 2012. Cannabis as a risk factor for self-harm has been incorporated into clinical risk assessment frameworks since.
- Original Title:
- The natural history of self-harm from adolescence to young adulthood: a population-based cohort study.
- Published In:
- Lancet (London, England), 379(9812), 236-43 (2012)
- Authors:
- Moran, Paul(3), Coffey, Carolyn(2), Romaniuk, Helena, Olsson, Craig, Borschmann, Rohan, Carlin, John B, Patton, George C
- Database ID:
- RTHC-00592
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Does cannabis cause self-harm?
This study found cannabis use during adolescence was independently associated with a 2.4-fold increased risk of self-harm, even after accounting for depression, anxiety, alcohol, and antisocial behavior. However, association does not prove causation.
Does self-harm in teenagers usually continue into adulthood?
Most self-harm that begins in adolescence resolves on its own during the transition to adulthood. However, teens with depression and anxiety symptoms were nearly 6 times more likely to continue self-harming into young adulthood.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-00592APA
Moran, Paul; Coffey, Carolyn; Romaniuk, Helena; Olsson, Craig; Borschmann, Rohan; Carlin, John B; Patton, George C. (2012). The natural history of self-harm from adolescence to young adulthood: a population-based cohort study.. Lancet (London, England), 379(9812), 236-43. https://doi.org/10.1016/S0140-6736(11)61141-0
MLA
Moran, Paul, et al. "The natural history of self-harm from adolescence to young adulthood: a population-based cohort study.." Lancet (London, 2012. https://doi.org/10.1016/S0140-6736(11)61141-0
RethinkTHC
RethinkTHC Research Database. "The natural history of self-harm from adolescence to young a..." RTHC-00592. Retrieved from https://rethinkthc.com/research/moran-2012-the-natural-history-of
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.