Study Links Low Oral Microbiome Diversity to Depression Symptoms - Video

New Delhi: Published in BMC Oral Health, a new study led by researchers at NYU Rory Meyers College of Nursing reveals that individuals with less diverse oral microbiomes are more likely to experience symptoms of depression. This research sheds light on the underexplored connection between oral bacteria and mental health.

The mouth, home to between 500 billion and 1 trillion bacteria, houses the second-largest community of microorganisms in the human body after the gut. This new research emphasizes that the oral microbiome may play a role in mood disorders.

To explore this connection, researchers examined data from over 15,000 U.S. adults aged 18 and older, drawn from the National Health and Nutrition Examination Survey (NHANES) conducted by the Centers for Disease Control and Prevention between 2009 and 2012. Participants completed surveys measuring depression symptoms, and provided saliva samples that underwent gene sequencing to identify bacterial content and assess microbiome diversity.

The study found that individuals with lower microbial diversity in their saliva were more likely to report symptoms of depression. Additional analysis revealed that factors such as smoking, alcohol use, and dental care habits—known to affect oral bacterial composition—also influenced the relationship between microbiome diversity and depression.

“It’s possible that the oral microbiome influences depressive symptoms through inflammation or changes to the immune system. Conversely, depression can drive changes including dietary intake, poor oral hygiene, increased smoking and drinking, or the use of medications—all of which have the potential to alter the oral microbiome,” said Bei Wu, vice dean for research at NYU Rory Meyers and senior author of the study.

While the direction of the relationship remains unclear, these findings open new avenues for research into mental health diagnostics and treatment.

Reference: Qiu, X., Xu, T., Huang, Y. et al. Relationship between depression and oral microbiome diversity: analysis of NHANES data (2009–2012). BMC Oral Health 25, 914 (2025). https://doi.org/10.1186/s12903-025-06274-x