Body site-specific associations between human skin microbiome composition and psychological wellbeing

BACKGROUND: There is increasing interest in understanding the interplay between psychological wellbeing and the human microbiome, with a particular focus on the impact of the gut microbiome on psychological health. However, the role of the skin microbiome remains underexplored. Our study addresses this gap by investigating the relationship between the human skin microbiome at various body sites (face, scalp, forearm, axilla) and psychological wellbeing. OBJECTIVES: To provide an understanding of the role of the skin microbiome in psychological health. METHODS: Fifty-three participants underwent microbiome sampling via skin swabbing of four body regions (forearm, face, scalp, axilla) and completed psychological measures of global/general wellbeing (Affect Grid, sleep quality, Stress Numerical Rating Scale-11, Perceived Stress Scale) and body site-related wellbeing (Hair & Scalp CARE, SkinCARE, UnderarmCARE). All bacterial DNA extracts were analysed using quantitative polymerase chain reaction and sequencing of the V1-V2 region of 16S. Microbial diversity was computed as Shannon diversity and Faith's phylogenetic diversity. Correlations were determined between psychological measures, microbial diversity and genera for each body site. RESULTS: Specific bacterial genera were associated with aspects of wellbeing. Cutibacterium spp. showed consistent associations with psychological wellbeing across multiple body locations. Increased abundance of Cutibacterium spp. on the face and axilla was associated with reduced stress, and an increased abundance of Cutibacterium spp. in the axilla was associated with increased mood pleasantness. CONCLUSIONS: Our findings highlight, for the first time, the nuanced relationship between the skin microbiome and psychological wellbeing. Increased abundance of Cutibacterium spp. across multiple body sites was consistently associated with positive wellbeing outcomes. This underscores the need for further investigation into specific bacterial taxa that may be involved in a skin-brain axis, as well as the importance of specific microbial communities on the body and their potential influence on this connection.