Kissing spreads depression and anxiety, says new study. But why? – Firstpost

Can kissing spread depression and anxiety?

It may sounds unbelievable, but this is what a recent study has found.

Researchers did so by studying the oral microbiome of over 250 newly-wedded couples.

But what do we know? What did researchers find?

Let’s take a closer look

What do we know?

The research was published in Exploratory Research and Hypothesis in Medicine.

It was led by independent researcher Reza Rastmanesh.

As per Jerusalem Post, the entire team included researchers from Italy, India, Iran, and Great Britain.

They study involved examining the oral microbiome – a diverse array of microorganisms that reside in the human mouth – of 268 newly-married couples in Iran.

“Given that bacterial transmission can occur between spouses, this study aimed to investigate whether the transmission of oral microbiota between newlywed couples mediates symptoms of depression and anxiety,” the researchers said,  as per New Atlas.

As per Daily Mail, the study was conducted from February 2024 to October 2024.

Patients were asked not to change any of the habits during the study.

At the beginning of the study, one partner was in good mental health while the other had issues such as anxiety and depression as well as insomnia.

Researchers studied the oral microbiome and measured cortisol in the saliva of all the participants on the first day of the research.

They also gave the couples mental health tests and used advanced DNA sequencing techniques to examine the mouth bacteria.

They then did so after six months and compared the two.

What did they find?

As per Daily Mail, the results found that the previously healthy spouses ’exhibited significantly higher scores for depression, anxiety, and insomnia compared to their own baseline measurements’.

In short, it found that the spouses who suffered from insomnia and mental health conditions “infected” the formerly healthy spouses.

According to Hindustan Times, the mouth bacteria in the formerly healthy spouse now looked more like their unhealthy partner at the beginning of the study.

The study found bacteria such as Clostridia, Veillonella, Bacillus, and Lachnospiraceae became more widespread in both partners.

These bacteria are linked to brain disorders, depression, anxiety, and sleep disturbances.

Scientists say these bacteria impact the brain by degrading the blood-brain barrier.

The study said women were more likely to be impacted than men.

The study also found that levels of cortisol had increased in the formerly healthy spouses.

So, what is to blame?

Kissing, the researchers said.

More specifically, the bacteria that was exchanged between the mouths of the spouses.

“Oral microbiota transfer between individuals in close contact, such as couples in the present study, may mediate depression and anxiety,” said the researchers, as per New Atlas. “We found that changes in oral microbiota composition are associated with changes in the severity of insomnia, salivary cortisol levels, and depression and anxiety scores. Our findings align with previous studies on salivary cortisol levels as well as depression and anxiety scores.”

However, the authors acknowledged several limitations with the study.

This included the fact that only Persian-peaking couples based in Iran were studied.

The study also did not take into account other external factors such as major life events and dietary changes.

They said more research is needed.

“Since this study is associational, further research is needed to establish whether this association is causal,” the researchers said. “If it is determined that this association is indeed causal, it could have significant implications for contemporary research.”

With inputs from agencies