Associations between oral microbiota pathogens and elevated depressive and anxiety symptoms in men

Background Systemic inflammation has been associated with depression. Certain oral bacterial species contribute to extra oral inflammation, however their potential association with mental disorders remains unclear. This study investigated the associations between oral microbiota pathogens and depressive and anxiety symptoms. Methods Data came from 436 men from the Geelong Osteoporosis Study. Using 16S rRNA gene sequencing, we characterized the oral microbiota composition and created a composite variable representing the prevalence of known oral pathogens, Porphyromonas gingivalis , Treponema denticola , Fusobacterium nucleatum , and Prevotella nigrescens . Binary variables were created representing elevated depressive and anxiety symptoms using the Hospital Anxiety and Depression Scale. Associations between oral pathogens and elevated depressive/anxiety symptoms were analyzed using logistic regression adjusted for confounders (age, socio-economic status, diet, smoking, alcohol, exercise, obesity and hypertension). Results We found limited evidence for an association between the pathogen composite and elevated depressive (N = 39) but not anxiety (N = 66) symptoms. Moreover, some of the comprising species, P. nigrescens (OR 1.61 (95% CI 1.21, 2.13)) and F. nucleatum (subsp. animalis ATCC 51191 (1.54 (1.13, 2.11)), subsp. animalis (1.47 (1.05, 2.08)) and subsp. vincentii (1.47 (1.06, 2.04))) were associated with elevated depressive symptoms. Exploratory analyses revealed several other taxa associated with depression and anxiety. Limitations This study focuses on mental health symptoms and not diagnoses in men, and the results may not be generalizable to women. Conclusions We identified several taxa within the oral microbiota that were associated with depressive and anxiety symptoms. Further replication and mechanistic studies are needed. Highlights A composite of oral pathogens is associated with depressive symptoms in adult men Associations between P. nigrescen s and other species and elevated depressive symptoms Associations remain following adjustment for confounders Oral microbial diversity was not associated with depressive or anxiety symptoms Fewer associations between oral microbial composition and anxiety than depression