215.3 - Salivary Microbiota is Associated with Cannabis Use in Adolescents

Brittney Browning (Medical University of South Carolina), Anna Kirkland (Medical University of South Carolina), Helen Liu (Medical University of South Carolina), ReJoyce Green (Medical University of South Carolina), Taylor Ticer (Medical University of South Carolina), Janiece Glover (Medical University of South Carolina), Melinda Engevik (Medical University of South Carolina), Lindsay Squeglia (Medical University of South Carolina)

Purpose: Cannabis is now the second most commonly used substance during adolescence, with 35.7% of 18-year-olds reporting use in the past year and 6.4% reporting daily use. Accumulating evidence suggests that cannabis use affects the microbiome, however, this is still underexplored. Given that adolescence is a vital period of neural and microbial development, it is essential to investigate if cannabis use is associated with differences in microbiota as perturbations to microbial systems during this period of development may influence brain development. 

Methods: Saliva biospecimens were collected from adolescent (15-19 years old) cannabis users (N=8) and control participants (N=9) in an ongoing clinical trial (K23 AA025399) at the Medical University of South Carolina. Bacterial quantification was performed by real-time quantitative PCR (qPCR) using primers for representative oral phyla (Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria) and related species (Staphylococcus, Clostridium coccoides, Clostridium leptum, Lactobacillus, Escherichia coli, Bacteroides, and Prevotella). Standard t-test was used to compare the relative abundances between the cannabis using group and control group. Correlations between levels of oral phyla and related species with cannabis use days reported on the Timeline Follow back (TLFB) and Cannabis Use Disorder Identification Test (CUDIT) scores were completed. 

Results: All saliva samples contained significant levels of bacterial gDNA (mean concentration: 96.9 ng/μl; ~10 ng/μl is sufficient). We observed significantly lower levels of Proteobacteria (p=0.031) and Bacteroides (p= 0.006) in the cannabis-using group compared to the non-cannabis-using control group. Additionally, the number of cannabis use days reported on the TLFB and CUDIT scores were inversely correlated with Bacteroides levels (p= lt;0.001, p=0.011 respectively). 

Conclusion: These preliminary data suggest that cannabis use during adolescence may be associated with changes in the oral microbiota, specifically in Proteobacteria and Bacteroides. The lower abundance of Bacteroides in the cannabis using group is further strengthened by the inverse correlations between cannabis use days and CUDIT scores. Interestingly, Bacteroides actively expresses GABA-producing pathways, a type of inhibitory neurotransmitter pathway that studies have shown is inhibited by THC. In addition, ratios of Bacteroides from stool microbiota analyses have also been reported to be decreased in cannabis users. Therefore, saliva microbiota collection may serve as a favorable alternative to classic stool collection. Inclusion of more participants in future studies will allow for more power to detect microbial differences within adolescents who use cannabis. 

Support or Funding Information

This project was made possible by an NIAAA-funded predoctoral fellowship (T32AA007474-34).