Depression And Anxiety Might Be Spread Through Kissing

Colds, mono, herpes—fine, we get it. They’re the standard hazards of kissing. But now you may have even more reason to choose who you lock lips with carefully, as scientists say depression and anxiety might be joining the list of transmissible conditions.

In a recent study published in Exploratory Research and Hypothesis in Medicine, Iranian scientists tracked 268 newlywed couples. When one partner reported depression, anxiety, and insomnia, the other—previously healthy—partner began showing similar symptoms after just six months. Their oral bacteria changed, too. Swabs taken from both partners showed that their microbiomes had started to match in surprisingly specific ways.

The connection lies in cortisol, the stress hormone. High cortisol levels can disrupt the bacterial balance in the mouth. Researchers believe that close contact, especially kissing, can transmit those disrupted microbiomes from one person to another.

Among the bacterial groups that appeared more frequently in affected couples were Clostridia, Veillonella, Bacillus, and Lachnospiraceae—all microbes linked to inflammation and mental health problems.

Women were especially vulnerable. Their mental health scores, measured using standard clinical scales, shifted in significant ways. They weren’t mirroring their partners exactly, but the direction was clear: more anxiety, more depression, worse sleep. And their bacterial DNA showed the same trend, moving closer to the microbial profile of their spouse.

This doesn’t mean kissing causes depression. But it does add weight to the idea that mental health symptoms can bleed into those closest to you in ways we don’t fully understand. Emotional strain might come with a microbial trail. And when your partner is carrying around altered bacteria tied to stress and poor sleep, your body could end up playing host, too.

Researchers say more work is needed to understand how these microbes behave and whether they play a role in other conditions like PTSD, bipolar disorder, or chronic fatigue. But the implications are unsettling. Love might come with shared playlists, shared bank accounts, and, apparently, shared oral ecosystems that carry more than nasty morning breath.

The study didn’t control for everything, though. Diet, underlying conditions, and other lifestyle factors were left out. But it opens the door to new questions. What else might we be passing between our mouths and minds? And how many of our private struggles are actually shared, down to the microscopic level?

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