Oral microbiota among treatment-naïve adolescents with depression: A case-control study

Adolescent depression has profound impacts on physical, cognitive, and emotional development. While gut microbiota changes have been linked to depression, the relationship between oral microbiota and depression remains elusive. Our study aims to investigate the oral microbiota in treatment-naïve adolescents experiencing depression and examine their potential associations with cognitive function.

Our case-control study comprised two groups of adolescents aged 12-17: the depression group, including treatment-naïve individuals diagnosed with DSM-5 major depressive disorder (MDD), and a healthy control group of non-depressed individuals (HC). Participants underwent structured neuropsychiatric assessments, and fasting morning saliva samples were collected for the 16S rRNA sequencing to investigate the oral microbiota.

Significant differences were identified in the α- and β-diversities of the oral microbiota between MDD and HC groups. Specific bacterial taxa, including genera Streptococcus, Neisseria, Hemophilus, Fusobacterium, and g_norank_f_norank_o_Absconditabacteriales_SR1, were significantly associated with MDD. The association extends to cognitive functions, where correlations were observed between certain oral bacteria and cognitive scores, including instant and delayed memory, visual breadth, and speech features for the combined MDD and HC individuals (p < 0.05). Random forest analysis identified ten genera of oral microbes with the highest predictive values for MDD. The area under the curve (AUC) is 0.78 in the receiver operating characteristic (ROC) curve analysis.

Our results highlight the oral microbiota's role as a biomarker for adolescent depression and its impact on cognitive functions. These insights underscore the need for further research into the links between oral health, mental health, and cognitive functions.