Kissing Your Spouse Could Transmit Anxiety and Depression, Study Suggests

A study of newlywed couples revealed that depression and anxiety may be transmitted between spouses through the oral microbiome, which is shared during close interactions like kissing.

How Oral Bacteria May Influence Mental and Physical Health

Researchers are increasingly discovering that, much like the gut microbiome, the oral microbiome—a complex mix of bacteria in our mouths—can influence both physical and mental health. Imbalances in this microbial community have been associated with conditions such as autism spectrum disorder, dementia, Parkinson’s disease, schizophrenia, anxiety, and depression.

A compelling new study explored whether kissing can transfer the oral microbiome between individuals—and if such microbial exchange could influence mental health.

“Since bacteria can be transmitted between spouses, this study set out to examine whether sharing oral microbiota among newlywed couples contributes to symptoms of anxiety and depression,” the researchers explained.

International Study Tracks Microbial and Mental Health Shifts in Newlywed Couples Over Six Months

The study was conducted by an international team from Iran, India, Italy, and the UK. Researchers initially screened 1,740 couples for insomnia. From that group, 268 couples who had been married for less than six months and were cohabiting were selected. In each pair, one partner was healthy, while the other had insomnia accompanied by anxiety and depression. Oral microbiome samples and salivary cortisol (a stress hormone) levels were collected on the first and 180th days of the study. Participants were instructed to maintain their normal diet, oral hygiene, and exercise routines throughout the research period.

After six months, the previously healthy spouses of affected partners exhibited higher scores for anxiety and depression, along with worse sleep quality—effects that were more pronounced in women. Though insomniac partners had initially higher cortisol levels, their healthy spouses also showed elevated levels by the end of the study, suggesting they were experiencing physiological signs of stress. Remarkably, the oral microbiome of the healthy spouses shifted over time to more closely resemble that of their affected partners.

Oral Bacteria Exchange in Couples Linked to Shifts in Mental Health and Stress Markers

“Close-contact oral microbiota transfer, like that seen between couples in this study, may contribute to the development of depression and anxiety,” the researchers concluded. “We observed that changes in oral bacterial composition were linked to variations in insomnia severity, cortisol levels, and mental health symptoms, supporting earlier findings in this area.”

The researchers noted that the transfer of oral microbiota between couples is plausible, especially considering other documented forms of physiological synchrony, such as aligned heart rhythms and shared sleep patterns. They believe their findings could inform more holistic, personalized, and preventive approaches to mental health care.

However, the study had several limitations. It relied on self-reported data to assess insomnia, anxiety, and depression; measured only morning salivary cortisol levels; and did not account for shared lifestyle factors like diet. Budget constraints also limited bacterial sampling to the tonsils and pharynx, rather than analyzing the full oral microbiome.

Despite these constraints, the study opens the door to compelling questions for future research.

“As this study only shows a correlation, more investigation is needed to determine whether the relationship is causal,” the researchers said. “If a causal link is confirmed, it could significantly impact future research and mental health strategies.”

Read the original article on: New Atlas

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