McNair Symposium

2025 McNair Research Symposium

Daniel Jones


A Systematic Review of Methylome-Wide Association Studies Examining Cannabis Use

Research suggests DNA methylation, an epigenetic modification that impacts gene expression, may be altered by cannabis. This systematic review sought to synthesize the literature on methylome-wide association studies (MWAS) of active cannabis use in humans. We screened 675 studies returned by Google Scholar search in June 2025 and identified 10 studies for inclusion. Analysis of the included studies revealed that the current literature is burdened by low sample sizes and restrictive cohorts, with five studies comparing fewer than 100 participants and 8 studies focusing primarily on cohorts with majority European ancestry. However, three studies overcame sampling limitations via meta-analysis of multiple cohorts. Another challenge unique to cannabis MWAS is tobacco use, as co-use is common. There was significant variation across studies when accounting for tobacco use. One consistently identified gene across studies was AHRR, a gene heavily associated with cigarette use. AHRR was identified in studies even when smoking was accounted for via stratification. Additionally, 4 studies identified significant enrichment in the dopaminergic synapse pathway. This enrichment was found in studies examining both current and former cannabis use. These findings highlight a need for larger sample sizes or meta-analyses in diverse populations to generate results with methylome-wide power that are generalizable to non-European populations. Additionally, future studies must utilize consistent definitions of cannabis use alongside consistent controls for smoking to better identify cannabis specific genes and pathways.

Faculty Mentor: Dr. Shaunna Clark

Dept. of Psychiatry & Behavioral Sciences

Texas A&M University College of Medicine

 Daniel Jones' poster

Daniel Jones