Cannabis exposure tracked with all four major mental health problems across US states and time periods
An analysis of 410,138 NSDUH respondents found cannabis exposure was significantly associated with all four measures of mental illness across US regions and time, with serious mental illness doubling as cannabis use increased.
Quick Facts
What This Study Found
Across 410,138 NSDUH respondents (76.7% response rate), cannabis exposure was significantly associated with any mental illness, major depression, serious mental illness (SMI), and suicidal ideation in geospatial models adjusted for demographics and other substance use. SMI rates doubled (3.62% to 7.06%) as cannabis use increased across regions. Cannabis decriminalization was associated with a 3.28% attributable fraction of SMI, and legalization with 12.91% attributable fraction.
Key Numbers
410,138 respondents; 76.7% response rate; SMI doubled from 3.62% to 7.06% with cannabis increase; decriminalization AFE 3.28%; legalization AFE 12.91%; significant for all 4 MH outcomes.
How They Did This
Ecological cohort study using NSDUH geographically-linked substate data (2010-2012 and 2014-2016) with two-stage geotemporospatial robust generalized linear regression and formal causal inference analysis.
Why This Research Matters
This is one of the first studies to apply formal causal inference methods to the cannabis-mental health relationship at a population level, finding dose-response and temporal-sequential relationships consistent with causation.
The Bigger Picture
If the causal inference is correct, cannabis legalization may be contributing measurably to population-level mental health burden. The 12.91% attributable fraction for serious mental illness under legalization would have substantial public health implications.
What This Study Doesn't Tell Us
Ecological design (associations at area level may not hold for individuals); cross-sectional components within the cohort; NSDUH is self-report; cannot control for all confounders at the individual level; causal inference methods applied to observational data have inherent limitations.
Questions This Raises
- ?Do individual-level longitudinal studies confirm these population-level associations?
- ?Would cannabis policies that limit THC potency reduce mental health impacts?
Trust & Context
- Key Stat:
- SMI doubled (3.62% to 7.06%) as cannabis use increased; legalization AFE 12.91%
- Evidence Grade:
- Moderate: very large sample with formal causal inference methods, but ecological design limits individual-level conclusions.
- Study Age:
- Published 2020.
- Original Title:
- Co-occurrence across time and space of drug- and cannabinoid- exposure and adverse mental health outcomes in the National Survey of Drug Use and Health: combined geotemporospatial and causal inference analysis.
- Published In:
- BMC public health, 20(1), 1655 (2020)
- Authors:
- Reece, Albert Stuart(5), Hulse, Gary Kenneth(5)
- Database ID:
- RTHC-02798
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis legalization increase mental illness?
This study found cannabis legalization was associated with a 12.91% attributable fraction of serious mental illness at the population level. Serious mental illness rates doubled as cannabis use increased across US regions. However, ecological data cannot definitively prove individual-level causation.
Which mental health conditions are linked to cannabis?
All four measured: any mental illness, major depression, serious mental illness, and suicidal ideation were significantly associated with cannabis exposure after adjusting for demographics and other substance use.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-02798APA
Reece, Albert Stuart; Hulse, Gary Kenneth. (2020). Co-occurrence across time and space of drug- and cannabinoid- exposure and adverse mental health outcomes in the National Survey of Drug Use and Health: combined geotemporospatial and causal inference analysis.. BMC public health, 20(1), 1655. https://doi.org/10.1186/s12889-020-09748-5
MLA
Reece, Albert Stuart, et al. "Co-occurrence across time and space of drug- and cannabinoid- exposure and adverse mental health outcomes in the National Survey of Drug Use and Health: combined geotemporospatial and causal inference analysis.." BMC public health, 2020. https://doi.org/10.1186/s12889-020-09748-5
RethinkTHC
RethinkTHC Research Database. "Co-occurrence across time and space of drug- and cannabinoid..." RTHC-02798. Retrieved from https://rethinkthc.com/research/reece-2020-cooccurrence-across-time-and
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.