A genetic analysis found that alcohol and nicotine dependence showed widespread genetic correlations with other psychiatric disorders, while cannabis use disorder was only significantly correlated with ADHD.
Psychiatric geneticists, addiction researchers, and clinicians interested in the biological basis of substance use disorders.
Cannabis use disorder genetically correlated only with ADHD
What the researchers found
Alcohol and nicotine dependence showed significant genetic correlations with multiple psychiatric disorders including ADHD, schizophrenia, and major depression. Cannabis use disorder was significantly associated only with ADHD. In factor analysis, all three substance use disorders loaded primarily on Factor 3, a heterogeneous factor that also included ADHD, major depression, autism spectrum disorders, and Tourette syndrome.
Why it matters
Understanding the genetic architecture of cannabis use disorder relative to other psychiatric conditions helps clarify whether CUD shares biological pathways with conditions like schizophrenia and depression, which has implications for treatment and risk assessment.
The numbers in context
11 psychiatric disorders analyzed. Cannabis use disorder significantly correlated only with ADHD. Alcohol and nicotine dependence correlated with multiple disorders. All SUDs loaded on Factor 3 in latent structure analysis.
How the study worked
GWAS summary statistics from 11 psychiatric disorders including alcohol dependence, nicotine dependence, and cannabis use disorder. Genetic correlations estimated via LD-Score Regression. Factor analysis of the genetic relationship matrix to identify latent structure.
What this study cannot tell us
GWAS summary statistics represent common variants only. CUD GWAS samples may be underpowered relative to other disorders. Genetic correlations do not establish causation. Factor models were somewhat unstable, as the authors acknowledge.
How to read the evidence
Robust genetic methodology using GWAS summary statistics, but potentially underpowered for CUD and limited to common genetic variants.
When this study was published
2021 genetic study. Highlights the need for larger cannabis use disorder GWAS to fully characterize its genetic architecture.
The bigger picture
The limited genetic overlap of CUD with other psychiatric disorders, compared to alcohol and nicotine, suggests cannabis use disorder may have a more distinct genetic architecture or that current GWAS sample sizes for CUD are too small to detect weaker correlations.
Questions still open
- Would larger CUD GWAS samples reveal additional genetic correlations? Does the CUD-ADHD genetic link reflect shared impulsivity pathways? Could genetic risk profiles help identify individuals at risk for developing CUD?
Common questions
Why was CUD only linked to ADHD genetically?
Does this mean cannabis is genetically separate from other addictions?
Read the original research
Genomic relationships across psychiatric disorders including substance use disorders.
Drug and alcohol dependence, 220, 108535
Citation
Abdellaoui, Abdel; Smit, Dirk J A; van den Brink, Wim; Denys, Damiaan; Verweij, Karin J H. (2021). Genomic relationships across psychiatric disorders including substance use disorders.. Drug and alcohol dependence, 220, 108535. https://doi.org/10.1016/j.drugalcdep.2021.108535
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