Can You Catch Depression From Your Partner? New Study Says Maybe

Marriage also tends to equal being totally in sync with your spouse, completing each other's sentences, sharing a laugh about the same jokes, and even mimicking each other's moods at times. But new research out of Iran suggests that there's another dimension of that closeness: sharing oral bacteria that influence mental health.

A just-published study in Exploratory Research and Hypothesis in Medicine hypothesizes that depression and anxiety can be transmitted from one spouse to another, at least partially, through shifts in the oral microbiota, the community of bacteria that inhabit the mouth.

When one spouse is struggling, so can the other.

The scientists tracked 1,740 couples who had just gotten married for six months. Of these, 268 were struggling with what the scientists referred to as a "depression-anxiety phenotype": depression, anxiety, and sleep disturbances. Their healthy spouses were also tracked for changes in mental health and oral microbes.

At the start, the healthy spouses didn't have any signs of mental illness. But after six months cohabiting with their infected spouse, they started complaining of much more depression, anxiety, and sleep disturbances. As a matter of fact, these changes preceded dramatic changes in their oral microbiome, which were similar to those of their ill spouses.

Bacteria change with daily intimacy.

Kissing, food sharing, and just hanging out together in close proximity can all help result in the sharing of millions of bacteria. Most of them are harmless or even beneficial, but the research singles out certain strains, including Clostridia, Veillonella, Bacillus, and Lachnospiraceae, as more prevalent in couples when a partner was showing signs of mental illness.

Earlier studies have associated the bacterial strains with anxiety, depression, and sleep disorders, possibly because of their impact on the brain by the "oral microbiota-brain axis", a mechanism that connects oral bacteria with brain function.

Women might be more impacted.

Female partners exhibited more significant declines in mental well-being and larger shifts in their oral microbiome than their male counterparts. They also retained higher cortisol levels,  the body's main stress hormone, indicating a more biological stress response.

Mental health is a two-way street.

This research contributes to mounting evidence demonstrating that lovers are biologically linked. Already, we know partners can become coupled in heart rates, sleep patterns, and stress reactions. Now, perhaps we have to add mental health as a shared axis of intimate relationships.

Treatment and therapy implications

If bacteria are involved in the transmission of mental health between couples, it creates a whole new area for treatment. Couples therapy may be combined with microbiome-targeting interventions, including specific probiotics or dietary modifications favoring health-promoting bacteria.

Nevertheless, the research has its limitations. It did not consider lifestyle issues such as diet or stress that is shared between partners, and it was only done with Persian-speaking couples in Tehran. It also doesn't establish the bacteria caused the changes, only that they were highly correlated.

The big picture

Whereas the notion of ​"catching" depression can be scary, this research holds out hope. If part of what causes mental illness is imbalances in microbes, then perhaps mental illness can be reversed. Treating both halves of a couple could be the key to improved mental health, for both, not only one.

References:

1. Wu, Ruixin, Xiaolin Liu, Yinuo Tan, Tianqiang Liu, Zhixiong Zhong, and Wei Tang. “Association Between Salivary Microbiota and Emotional States in Couples: Evidence of Bacterial Transmission Through Intimate Kissing.” Exploration of Reproductive Health Medicine 3, no. 2 (2025). https://www.xiahepublishing.com/2472-0712/ERHM-2025-00013.

2. Study Finds. “You Could ‘Catch’ Your Partner’s Depression Through Kissing, Study Suggests.” Study Finds, May 13, 2025. https://studyfinds.org/depression-transmitted-by-kissing-mouth-bacteria/.
   

(Input from various sources)

(Rehash/Muhammad Faisal Arshad/MSM)