Genetic analysis finds ADHD causally increases cannabis use risk nearly 8-fold, not the other way around
A Mendelian randomization study using data from over 85,000 individuals found ADHD genetically causes an 8-fold increased risk of lifetime cannabis use, with 29% genetic correlation between the two conditions.
Quick Facts
What This Study Found
Using GWAS data from 53,293 ADHD and 32,330 cannabis use subjects, genetic correlation between ADHD and lifetime cannabis use was r2=0.29 (p=1.63×10-5). Four new genome-wide significant loci were identified in cross-trait analysis. Mendelian randomization provided evidence that ADHD is causal for cannabis use (OR=7.9 for cannabis use in ADHD vs non-ADHD, 95% CI 3.72-15.51, p=5.88×10-5). The reverse direction was not supported.
Key Numbers
N=85,623; genetic correlation r2=0.29; ADHD→cannabis OR=7.9 (CI 3.72-15.51); 4 new genome-wide significant loci; 2 from single variant analysis, 2 from gene-based analysis.
How They Did This
Genome-wide association study meta-analyses with LD score regression for genetic correlation, cross-trait association analysis for shared loci, and two-sample Mendelian randomization for causal inference using summary statistics.
Why This Research Matters
Published in Molecular Psychiatry, this provides the strongest evidence yet that ADHD drives cannabis use, not the reverse. This has implications for treatment: addressing ADHD symptoms may be the most effective cannabis prevention strategy in this population.
The Bigger Picture
The 8-fold genetic risk from ADHD to cannabis use is substantial. If ADHD is a causal driver of cannabis use, then the high rates of cannabis use in ADHD populations are not a separate problem to manage but a downstream consequence of untreated or undertreated ADHD.
What This Study Doesn't Tell Us
Mendelian randomization assumes genetic instruments are valid (pleiotropic effects possible); lifetime cannabis use is a binary measure (does not capture dose or problematic use); European ancestry GWAS data limits generalizability; ADHD phenotype in GWAS may not represent clinical ADHD.
Questions This Raises
- ?Would effective ADHD treatment in childhood prevent cannabis use in adolescence?
- ?Are specific ADHD subtypes (inattentive vs hyperactive) differentially associated with cannabis use?
Trust & Context
- Key Stat:
- ADHD causes 8-fold cannabis use risk (Mendelian randomization, N=85,623)
- Evidence Grade:
- Strong: Mendelian randomization in Molecular Psychiatry with large GWAS samples and multiple analytical approaches.
- Study Age:
- Published 2020.
- Original Title:
- Attention-deficit/hyperactivity disorder and lifetime cannabis use: genetic overlap and causality.
- Published In:
- Molecular psychiatry, 25(10), 2493-2503 (2020)
- Authors:
- Soler Artigas, María(2), Sánchez-Mora, Cristina(3), Rovira, Paula(2), Richarte, Vanesa, Garcia-Martínez, Iris, Pagerols, Mireia, Demontis, Ditte, Stringer, Sven, Vink, Jacqueline M, Børglum, Anders D, Neale, Benjamin M, Franke, Barbara, Faraone, Stephen V, Casas, Miguel, Ramos-Quiroga, Josep Antoni, Ribasés, Marta
- Database ID:
- RTHC-02855
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does ADHD cause cannabis use?
Genetically, yes. This study found ADHD is causal for cannabis use with an 8-fold increased risk, meaning ADHD genetic variants predict future cannabis use. The reverse (cannabis causing ADHD) was not supported.
What does 29% genetic correlation mean?
It means ADHD and cannabis use share about 29% of their genetic architecture. Some of the same genes that increase ADHD risk also increase cannabis use risk, and 4 specific shared genetic loci were identified.
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Cite This Study
https://rethinkthc.com/research/RTHC-02855APA
Soler Artigas, María; Sánchez-Mora, Cristina; Rovira, Paula; Richarte, Vanesa; Garcia-Martínez, Iris; Pagerols, Mireia; Demontis, Ditte; Stringer, Sven; Vink, Jacqueline M; Børglum, Anders D; Neale, Benjamin M; Franke, Barbara; Faraone, Stephen V; Casas, Miguel; Ramos-Quiroga, Josep Antoni; Ribasés, Marta. (2020). Attention-deficit/hyperactivity disorder and lifetime cannabis use: genetic overlap and causality.. Molecular psychiatry, 25(10), 2493-2503. https://doi.org/10.1038/s41380-018-0339-3
MLA
Soler Artigas, María, et al. "Attention-deficit/hyperactivity disorder and lifetime cannabis use: genetic overlap and causality.." Molecular psychiatry, 2020. https://doi.org/10.1038/s41380-018-0339-3
RethinkTHC
RethinkTHC Research Database. "Attention-deficit/hyperactivity disorder and lifetime cannab..." RTHC-02855. Retrieved from https://rethinkthc.com/research/soler-2020-attentiondeficithyperactivity-disorder-and-lifetime
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.