The adolescent and young adult microbiome and its association with substance use: a scoping review

Abstract

Aims The microbiome is a critical factor in health throughout human development. The aims of this scoping review are to (i) elucidate the differences between the youth (post-natal day 21–65 for rodents, 2–7 years for non-human primates, and 10–25 years for humans) microbiome with other life stages and (ii) identify youth-specific microbial changes associated with substance use. Methods Peer-reviewed studies published up to May 2023 were identified in PubMed and SCOPUS and included gut and oral microbiome studies from rodents, non-human primates, and humans (N = 1733). Twenty-six articles were determined eligible based on inclusion criteria (aim 1: n = 19, aim 2: n = 7). Results The adolescent and young adult oral and gut microbiomes are distinct compared to other life stages, within both non-human and human models. While there is limited research in this area, the microbiome appears to be vulnerable to substance use exposure earlier in life, including substances commonly initiated and escalated during adolescence and young adulthood (i.e. alcohol, cannabis, and tobacco). Conclusions Studies across the lifespan indicate that adolescence and young adulthood are distinct periods of development, where the microbiome is sensitive to exposures, including substance use. There is a need for more studies focused on the adolescent and young adult microbiome and substance use, as well as focused on the oral microbiome during this developmental period. Understanding the gut and oral microbiome during adolescence and young adulthood may provide insight into the pathophysiology of substance use disorders.

Innovative Biomarkers for Obesity and Type 1 Diabetes Based on Bifidobacterium and Metabolomic Profiling

“…However, the same methodology could be expanded to adults. Studies suggest that the gut microbiome can be significantly different between children and adults [36,37]. Therefore, further studies would need to be carried out to understand if the same markers can be observed in adults as in children, or to identify the ones more relevant to specific age groups.…”

Adolescent alcohol use is associated with differences in the diversity and composition of the oral microbiome

“…The brain undergoes significant structural and functional changes (e.g., changes in brain structural volume, cortical thickness, and myelination) and does not finish maturing until early adulthood (Casey et al., 2008). Similarly, both the gut and oral microbiomes mature during adolescence, experiencing alterations in the number of bacteria and their distribution (diversity) and the specific types of bacteria and their abundances (composition) (Browning et al., 2024; McVey Neufeld et al., 2016). Importantly, key neurodevelopmental trajectories overlap with a timeframe of peak plasticity in the gut and oral microbiomes (Cowan et al., 2020; Stahringer et al., 2012).…”

“…Studies have shown that germ free mice, mice raised in sterile conditions with no microbiome, have deficits in many areas of brain development and function, including effects on myelination, neurotransmission, synaptic plasticity, microglia function, neurogenesis, dendritic growth, and blood–brain barrier permeability (Cryan et al., 2019). In addition, the adolescent gut and oral microbiomes are particularly sensitive to environmental exposures, including alcohol and other substances (Browning et al., 2024). This suggests adolescence may be a crucial period of development where perturbations to the microbiome can lead to long‐term neural changes that could increase vulnerability for the development of AUD.…”

“…Although the associations between the oral and gut microbiomes with alcohol have been investigated in adults, there is a notable gap in adolescent‐specific research focused on this area. A scoping review conducted by our lab revealed only three human studies investigating the relationship between alcohol use and the microbiome in adolescents (Browning et al., 2024). Of these, only one study examined the oral microbiome; however, this particular study did not recruit participants specifically to evaluate differences related to alcohol consumption, lacked details on the quantity of alcohol consumed, and did not explore differences in microbiome diversity (Willis et al., 2018).…”