More Frequent Cannabis Use Predicted Worsening Suicidal Thoughts in Bipolar Disorder
In a longitudinal cohort of people with bipolar disorder, increases in cannabis use frequency predicted higher suicidal ideation at subsequent timepoints.
Quick Facts
What This Study Found
When a person had more frequent and intense cannabis use compared to their average, they had higher suicidal ideation at the next timepoint. Alcohol and substance use impairment also predicted future suicidal ideation. Cocaine frequency/intensity and substance use impairment were concurrently associated with suicidal ideation.
Key Numbers
788 participants with BSD. Median enrollment: 72 months. BD I: n=565, BD II: n=162, BD NOS: n=61. Cannabis use intensity/frequency predicted next-timepoint SI. Alcohol/substance impairment predicted next-timepoint SI. Cocaine I/F concurrently associated with SI.
How They Did This
Longitudinal cohort of 788 participants with bipolar I (n=565), bipolar II (n=162), and BD NOS (n=61) with median enrollment of 72 months. Alcohol and substance use measured via modified AUDIT every 6 months. Suicidal ideation measured via PHQ-9 item 9 every 2 months. Dynamic structural equation models tested prospective associations.
Why This Research Matters
Suicidal ideation is a major concern in bipolar disorder. This study provides prospective evidence that within-person increases in cannabis use precede worsening suicidal thoughts, which has implications for monitoring and clinical guidance.
The Bigger Picture
The within-person design is important because it shows that when the same individual uses more cannabis than usual, their suicidal thinking increases. This is stronger evidence than cross-sectional comparisons between people, though still cannot prove causation.
What This Study Doesn't Tell Us
Observational design cannot establish causation. Cannabis use measured every 6 months while SI measured every 2 months, creating temporal resolution mismatch. Self-reported substance use. Potential for reverse causation (increased SI driving cannabis use).
Questions This Raises
- ?Does cannabis use cause increased SI, or does worsening mood drive both cannabis use and SI?
- ?Would monitoring cannabis use changes improve suicide risk assessment in bipolar disorder?
Trust & Context
- Key Stat:
- Evidence Grade:
- Large longitudinal cohort with within-person analysis and sophisticated modeling, though measurement timing mismatch and observational design limit to moderate.
- Study Age:
- Data from a long-term bipolar disorder cohort study.
- Original Title:
- Alcohol and substance use differentially impact suicidal ideation in a longitudinal cohort of bipolar disorder.
- Published In:
- Psychiatry research, 344, 116357 (2025)
- Authors:
- Smith, Julia L, McInnis, Melvin G, Sperry, Sarah H
- Database ID:
- RTHC-07682
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
Does cannabis make suicidal thoughts worse in bipolar disorder?
This study found that when individuals with bipolar disorder used more cannabis than their own average, their suicidal ideation increased at the next measurement point. However, the study cannot prove causation.
Is cannabis uniquely risky for bipolar disorder?
Cannabis was one of several substances linked to suicidal ideation in this study. Alcohol and substance use impairment also predicted future suicidal thoughts. The findings suggest that monitoring all substance use is important in bipolar disorder.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-07682APA
Smith, Julia L; McInnis, Melvin G; Sperry, Sarah H. (2025). Alcohol and substance use differentially impact suicidal ideation in a longitudinal cohort of bipolar disorder.. Psychiatry research, 344, 116357. https://doi.org/10.1016/j.psychres.2025.116357
MLA
Smith, Julia L, et al. "Alcohol and substance use differentially impact suicidal ideation in a longitudinal cohort of bipolar disorder.." Psychiatry research, 2025. https://doi.org/10.1016/j.psychres.2025.116357
RethinkTHC
RethinkTHC Research Database. "Alcohol and substance use differentially impact suicidal ide..." RTHC-07682. Retrieved from https://rethinkthc.com/research/smith-2025-alcohol-and-substance-use
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.