Cannabis Abuse Quadrupled the Risk of Developing Depression Over 15 Years, While Depression Did Not Predict Cannabis Use
In a 15-year follow-up of 1,920 adults, those who abused cannabis at baseline were four times more likely to develop depression, including suicidal thoughts, while baseline depression did not predict future cannabis abuse.
Quick Facts
What This Study Found
Researchers leveraged a 15-year follow-up of the Baltimore Epidemiologic Catchment Area study to test a crucial question: does cannabis cause depression, or do depressed people self-medicate with cannabis?
The answer was one-directional. Among 849 people with no depression at baseline, those with cannabis abuse were four times more likely to develop depressive symptoms over the follow-up period, after adjusting for age, gender, antisocial symptoms, and other covariates. The depressive symptoms included suicidal ideation and anhedonia (inability to feel pleasure).
Critically, the reverse direction was not supported. Among 1,837 people with no cannabis abuse at baseline, depression did not significantly predict future cannabis abuse. This asymmetry argued against the self-medication hypothesis and suggested cannabis abuse is a genuine risk factor for depression rather than a consequence of it.
Key Numbers
1,920 participants. 15-year follow-up. Cannabis abusers: 4x more likely to develop depression. Suicidal ideation and anhedonia specifically elevated. Reverse direction (depression to cannabis): not significant.
How They Did This
Prospective cohort study using the Baltimore ECA dataset. 1,920 participants assessed in 1980 and reassessed 1994-1996 (15-year follow-up). Two cohorts analyzed: those without depression at baseline (N=849) and those without cannabis abuse at baseline (N=1,837). Diagnostic Interview Schedule assessed symptoms.
Why This Research Matters
The bidirectional analysis was methodologically powerful: by testing both directions of the association and finding that only cannabis-to-depression was significant, the study provided some of the strongest evidence that cannabis abuse genuinely increases depression risk rather than merely co-occurring with it.
The Bigger Picture
This study became a frequently cited reference in the cannabis-depression literature. The four-fold risk increase and the specificity of suicidal ideation as an outcome made it particularly relevant to public health discussions about cannabis use.
What This Study Doesn't Tell Us
The 15-year gap between assessments means intervening variables could explain the association. Cannabis "abuse" is a specific diagnostic category that may not represent all use patterns. The baseline assessment was in 1980 with different cannabis potency. Adjusted for several confounders but residual confounding is possible.
Questions This Raises
- ?What mechanism explains the cannabis-depression link?
- ?Would the association hold for cannabis use (not just abuse)?
- ?Does the risk vary with frequency, duration, or potency of use?
- ?Could the suicidal ideation finding inform screening protocols?
Trust & Context
- Key Stat:
- Cannabis abusers were 4x more likely to develop depression over 15 years
- Evidence Grade:
- A 15-year prospective population study with bidirectional analysis and confounder adjustment. Strong design, though the long gap between assessments limits precision.
- Study Age:
- Published in 2001 using data from 1980-1996. Cannabis products and usage patterns have changed substantially, potentially affecting the risk relationship.
- Original Title:
- Cannabis abuse as a risk factor for depressive symptoms.
- Published In:
- The American journal of psychiatry, 158(12), 2033-7 (2001)
- Authors:
- Bovasso, G B
- Database ID:
- RTHC-00102
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 depression?
In this study, cannabis abuse at baseline quadrupled the risk of developing depression over 15 years. Importantly, depression at baseline did not predict future cannabis abuse, suggesting the direction is from cannabis to depression rather than self-medication.
What types of depression were associated?
Suicidal ideation and anhedonia (inability to feel pleasure) were specifically elevated among those who developed depression after baseline cannabis abuse.
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Cite This Study
https://rethinkthc.com/research/RTHC-00102APA
Bovasso, G B. (2001). Cannabis abuse as a risk factor for depressive symptoms.. The American journal of psychiatry, 158(12), 2033-7.
MLA
Bovasso, G B. "Cannabis abuse as a risk factor for depressive symptoms.." The American journal of psychiatry, 2001.
RethinkTHC
RethinkTHC Research Database. "Cannabis abuse as a risk factor for depressive symptoms." RTHC-00102. Retrieved from https://rethinkthc.com/research/bovasso-2001-cannabis-abuse-as-a
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.