In a Norwegian cohort of 1,988 young people followed over 13 years, within-person increases in cannabis use were associated with increased anxiety, depression, and over 3-fold higher suicidal ideation risk in males, and increased anxiety and suicidal ideation in females.
Adolescent mental health clinicians; public health researchers studying cannabis and suicidality.
3.4x suicidal ideation risk with heavy cannabis use in young males
What the researchers found
Using fixed-effects models (which control for all stable individual characteristics), increasing cannabis use from none to 10+ times/year was associated in males with anxiety (RR 1.72, p=0.009), depressed mood (RR 1.49, p<0.001), and suicidal ideation (RR 3.43, p=0.012). In females, the same increase was associated with anxiety (RR 1.38, p=0.023) and suicidal ideation (RR 2.47, p=0.002). Only for depression was the gender difference statistically significant.
Why it matters
Fixed-effects models are among the strongest observational designs because they control for all stable individual characteristics (genetics, personality, early environment). The finding that cannabis use changes track with mental distress changes within the same person strengthens the case for a direct relationship.
The numbers in context
1,988 respondents. 4 waves over 13 years (1992-2005). 60% cumulative response rate. Males: anxiety RR 1.72, depression RR 1.49, suicidal ideation RR 3.43. Females: anxiety RR 1.38, suicidal ideation RR 2.47. Male depression association was significantly stronger than female.
How the study worked
Longitudinal cohort assessed at 4 time points over 13 years (1992-2005). 1,988 Norwegian respondents aged 11-18 at baseline. Fixed-effects modeling examining within-person associations between changes in cannabis use and changes in mental distress.
What this study cannot tell us
1990s cohort may not represent current cannabis use patterns (potency has increased). 60% response rate. Self-reported measures. Cannot definitively exclude reverse causation even with fixed-effects (mental distress changes could trigger cannabis use changes within waves). Norwegian context.
How to read the evidence
Longitudinal within-person design controlling for stable individual factors. Strong methodology but 1990s cohort and self-report.
When this study was published
2024 study
The bigger picture
The over 3-fold increase in suicidal ideation risk with heavy cannabis use in males is particularly concerning. Combined with the within-person design, this provides some of the strongest evidence to date linking cannabis use changes to suicidality changes during young adulthood.
Questions still open
- Would these effects be larger with today's higher-potency cannabis? What drives the stronger depression association in males?
Common questions
What are fixed-effects models?
Why are males more affected?
Read the original research
Associations Between Cannabis Use and Mental Distress in Young People: A Longitudinal Study.
The Journal of adolescent health : official publication of the Society for Adolescent Medicine, 74(3), 479-486
Citation
Gripe, Isabella; Pape, Hilde; Norström, Thor. (2024). Associations Between Cannabis Use and Mental Distress in Young People: A Longitudinal Study.. The Journal of adolescent health : official publication of the Society for Adolescent Medicine, 74(3), 479-486. https://doi.org/10.1016/j.jadohealth.2023.10.003
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