Marijuana and depression together have additive negative effects on verbal memory and brain structure
Young adults with both marijuana use and major depressive disorder showed worse verbal recall and thinner cortex in the middle temporal gyrus compared to those with either condition alone.
Quick Facts
What This Study Found
MDD and marijuana use had additive effects on memory recall and cortical thickness in the middle temporal gyrus. MDD alone (but not marijuana alone) was associated with poorer initial learning, fewer words recalled, more intrusion errors, and lower retention. The combination produced the worst outcomes.
Key Numbers
141 participants ages 18-25. Additive effects on verbal recall and middle temporal gyrus thickness. MDD alone associated with poorer learning, fewer words recalled, more intrusion errors.
How They Did This
Cross-sectional study of 141 young adults (ages 18-25) in four groups: marijuana only (n=46), MDD only (n=23), MDD + marijuana (n=24), and healthy controls (n=48). Participants completed the California Verbal Learning Test and a subset (n=82) underwent structural MRI.
Why This Research Matters
Depression and marijuana use frequently co-occur in young adults. Finding that their effects are additive rather than redundant suggests that marijuana use among people with depression carries an extra cognitive cost.
The Bigger Picture
Young adults with depression may use marijuana for symptom relief, but this study suggests doing so may compound their cognitive difficulties rather than helping.
What This Study Doesn't Tell Us
Cross-sectional design cannot determine causation. The MDD and MDD+MJ groups were smaller than the other groups. The MRI subsample was 82 of 141 participants.
Questions This Raises
- ?Would marijuana cessation in depressed individuals reverse the additive cognitive effects?
- ?Does the severity or frequency of marijuana use modulate the interaction?
- ?Are the cortical thickness changes permanent?
Trust & Context
- Key Stat:
- MDD + marijuana produced the worst verbal memory and cortical thickness
- Evidence Grade:
- Moderate: well-designed cross-sectional study with neuroimaging, but small group sizes and non-longitudinal design.
- Study Age:
- Published in 2019.
- Original Title:
- Marijuana use and major depressive disorder are additively associated with reduced verbal learning and altered cortical thickness.
- Published In:
- Cognitive, affective & behavioral neuroscience, 19(4), 1047-1058 (2019)
- Authors:
- Radoman, Milena, Hoeppner, Susanne S, Schuster, Randi M(9), Evins, A Eden, Gilman, Jodi M
- Database ID:
- RTHC-02247
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
What does "additive" mean here?
It means the negative effects of marijuana and depression on the brain and memory stack on top of each other. Having both conditions was worse than having either one alone.
Did marijuana alone affect verbal memory?
Marijuana alone was not significantly associated with poorer learning or recall in this study. It was only in combination with depression that the additive effects emerged.
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Cite This Study
https://rethinkthc.com/research/RTHC-02247APA
Radoman, Milena; Hoeppner, Susanne S; Schuster, Randi M; Evins, A Eden; Gilman, Jodi M. (2019). Marijuana use and major depressive disorder are additively associated with reduced verbal learning and altered cortical thickness.. Cognitive, affective & behavioral neuroscience, 19(4), 1047-1058. https://doi.org/10.3758/s13415-019-00704-4
MLA
Radoman, Milena, et al. "Marijuana use and major depressive disorder are additively associated with reduced verbal learning and altered cortical thickness.." Cognitive, 2019. https://doi.org/10.3758/s13415-019-00704-4
RethinkTHC
RethinkTHC Research Database. "Marijuana use and major depressive disorder are additively a..." RTHC-02247. Retrieved from https://rethinkthc.com/research/radoman-2019-marijuana-use-and-major
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.