23/07/2025
A recent large-scale study has uncovered a surprising connection between the microbes in your mouth and your mental health. Scientists examined the oral microbiome of over 15,000 adults and found that people with lower bacterial diversity in their mouths were more likely to show symptoms of depression. The link was particularly noticeable in men and non-Hispanic White individuals.
While it’s already known that the gut microbiome plays a role in emotional health, this research highlights the mouth as the body’s second-largest microbial community — a previously underestimated player in mental well-being. These oral bacteria play key roles in regulating inflammation and supporting the immune system, both of which are known to influence mood.
The study focused on "alpha diversity," which refers to the number of different bacterial species in the mouth. Individuals with higher bacterial diversity reported fewer symptoms such as persistent sadness and low energy. However, more diversity didn’t always mean better mood — there seems to be an ideal range. Interestingly, people with depression had significantly different oral bacteria profiles compared to those without.
While this doesn’t confirm whether oral health causes depression or vice versa, it points to an important connection. Maintaining good oral hygiene and exploring probiotic interventions could one day support mental health as well.
