Scientists: depression and anxiety can be transmitted through kisses

A group of scientists from Iran, India, Italy, and the United Kingdom found that depression and anxiety can be transmitted through oral bacteria - in particular, through kisses.

The study showed: after just six months of living together with a person suffering from these mental disorders, a healthy spouse may develop similar symptoms.

As reported by BAKU.WS, the work was published in the journal Exploratory Research and Hypothesis in Medicine. It describes the analysis of data from 1,740 couples who have been married for an average of about six months. Among them, 268 people were completely healthy, while their partners suffered from depression, anxiety, and insomnia. Participants completed standardized tests and provided saliva samples to assess stress hormone levels and analyze the oral microbiome using DNA sequencing.

It was found that over time, healthy partners showed significantly worsened indicators of anxiety, depression, and sleep quality. At the same time, the composition of their microbiome increasingly resembled the microflora of their spouses with mental disorders. Bacteria from the families Clostridia, Veillonella, Bacillus, and Lachnospiraceae were particularly active in multiplying in the oral cavity, which can weaken the blood-brain barrier and, according to scientists, affect brain function.

Every kiss, meal, or simply breathing near each other is a way to exchange millions of bacteria. According to researchers, this transfer of microflora can partially explain why one partner in a couple may develop depression and anxiety.

Interestingly, women were more susceptible to this process: they showed more pronounced changes in the microbiome and deterioration of mental state. Additionally, during the experiment, healthy spouses from these couples showed an increase in cortisol levels - the stress hormone - which also indicates the activation of stress reactions in the body.

Scientists believe that their discovery will help better understand the biological mechanisms of the spread of mental disorders in close relationships and will be useful in making recommendations for psychologists and therapists.