Genome-wide study found DNA methylation changes from cannabis use disorder in veterans, amplified by co-occurring PTSD | Research

The takeaway

In 2,310 Iraq/Afghanistan veterans, four DNA methylation sites were linked to lifetime cannabis use disorder even after controlling for smoking, and the combination of CUD and PTSD produced significantly greater methylation changes than either condition alone.

VA researchers studying dual diagnosis biology; epigeneticists investigating substance-stress interactions.

CUD + PTSD combination amplified DNA methylation changes

What the researchers found

Four CpGs were associated with lifetime CUD after smoking adjustment: AHRR cg05575921, LINC00299 cg23079012, VWA7 cg22112841, and FAM70A cg08760398. The AHRR site remained significant even in never-smokers. CUD interacted with PTSD status: veterans with both CUD and PTSD showed significantly lower DNA methylation than those with either condition alone. Preliminary evidence suggested AHRR methylation helps explain the association between CUD and psychiatric diagnoses, particularly mood disorders.

Why it matters

This is the first study showing that CUD and PTSD interact epigenetically, producing greater methylation changes together than either alone. This biological synergy may explain why veterans with dual diagnoses have worse outcomes.

The numbers in context

2,310 veterans (1,109 NHB, 1,201 NHW). 4 significant CpG sites. AHRR cg05575921 significant even in never-smokers. CUD + PTSD interaction: lower methylation than CUD alone, PTSD alone, or controls. AHRR methylation mediated CUD-psychiatric diagnosis association.

How the study worked

Epigenome-wide association study in 2,310 Iraq/Afghanistan era veterans (1,109 non-Hispanic Black, 1,201 non-Hispanic White) enriched for PTSD. Analysis of lifetime CUD controlling for current smoking. CUD x PTSD interaction analysis and mediation testing.

What this study cannot tell us

Cross-sectional design cannot determine whether methylation changes are cause or consequence. Iraq/Afghanistan veteran cohort may not generalize to civilians. Blood-based methylation may not reflect brain tissue. Enrichment for PTSD may affect generalizability of CUD findings.

How to read the evidence

Large veteran cohort with trans-ethnic analysis and careful smoking control. Cross-sectional design limits causal inference.

When this study was published

2024 study

The bigger picture

If CUD and PTSD amplify each other's epigenetic effects, targeted epigenetic interventions or early treatment of one condition might prevent the amplified biological changes that drive worse outcomes in dually diagnosed veterans.

Questions still open

Do these methylation changes reverse with CUD treatment? Could epigenetic markers help identify veterans at highest risk for dual diagnosis complications?

Common questions

Why does the AHRR gene keep appearing in cannabis studies?

AHRR (aryl hydrocarbon receptor repressor) is strongly affected by inhaled substances. Its methylation changes with both tobacco and cannabis smoking. This study showed its association with CUD persists even in veterans who never smoked tobacco.

What does the CUD-PTSD interaction mean clinically?

Veterans with both conditions show greater biological changes than expected from either alone. This may explain why treating one condition without addressing the other often yields poor outcomes in dually diagnosed veterans.

Read the original research

Genome-wide DNA methylation analysis of cannabis use disorder in a veteran cohort enriched for posttraumatic stress disorder.

Psychiatry research, 333, 115757

View on PubMed ↗Publisher’s paper ↗

Citation

Garrett, Melanie E; Dennis, Michelle F; Bourassa, Kyle J; Hauser, Michael A; Kimbrel, Nathan A; Beckham, Jean C; Ashley-Koch, Allison E. (2024). Genome-wide DNA methylation analysis of cannabis use disorder in a veteran cohort enriched for posttraumatic stress disorder.. Psychiatry research, 333, 115757. https://doi.org/10.1016/j.psychres.2024.115757