Oral microbiome composition, but not diversity, is associated with adolescent anxiety and depression symptoms.

PURPOSE: Depression and anxiety are highly prevalent disorders, whose significant burden is compounded by the presence of oral disease. Mental health disorders and oral health may be associated via changes to the oral microbiome, involving increased pro-inflammatory communication and cortisol in saliva. The present study provides the first culture-independent investigation of the oral microbiome considering depression and anxiety symptoms in adolescence, a critical age where these conditions begin to emerge and co-occur. It also investigates whether inflammation and cortisol moderate these relationships. METHODS: Participants (N = 66) aged 14-18 years (69.70% female) self-reported oral health, depression and anxiety symptoms, and collected saliva samples across two days. Saliva was assayed for cortisol and C-reactive protein (CRP), and used for 16S rRNA gene sequencing to estimate the oral microbiome. Multivariate statistical analyses examined associations. RESULTS: Overall diversity of the oral microbiome did not differ between adolescents by anxiety or depression grouping (low versus high symptoms), and was not associated with symptom measures. Depression and anxiety symptoms were instead associated with differential abundance of specific bacterial taxa, including Spirochaetaceae, Actinomyces, Treponema, Fusobacterium and Leptotrichia spp. Several host mood-microbial relationships were moderated by proposed mechanisms, including salivary cortisol and CRP. CONCLUSIONS: Oral microbiome composition, but not diversity, was associated with adolescent anxiety and depression symptoms. Longitudinal studies considering these associations would improve mechanistic understanding. This research indicates that adolescence remains an essential developmental period to identify early targets for intervention.

Bullying the Brain? Longitudinal Links Between Childhood Peer Victimization, Cortisol, and Adolescent Brain Structure.

Background: Childhood peer victimization is a stressful life experience associated with long-lasting adverse psychological consequences. While there is some evidence that victimization is associated with alterations in brain function, little is known about effects on brain structure. This study explored the relationships between childhood peer victimization, cortisol, and adolescent ventrolateral prefrontal cortex (vlPFC) structure in a sample of healthy children. Methods: A total of 50 (M age = 9.29 years at baseline) children participated in this longitudinal study. We examined whether diurnal cortisol levels (assessed at baseline) moderated the link between children's self-reported peer victimization (assessed at baseline) and vlPFC surface area, gray matter volume, and thickness 5 years later. Results: For boys, cortisol levels moderated the association between victimization and brain structure. For boys with a low daily cortisol output (assessed as area under the curve; AUC), high victimization was associated with a smaller right vlPFC surface area, and for boys with a high AUC, high victimization was associated with a larger right vlPFC surface area. In addition, for boys with a steeper diurnal slope, high victimization was associated with a smaller right vlPFC surface area, and for boys with a low flatter diurnal slope, high victimization was associated with a larger right vlPFC surface area. Conclusion: These results indicate the differential influence of cortisol on the relationship between victimization and brain structure. Findings suggest that victimization may have differential effects on brain development in boys who are more versus less biologically sensitive to stress.