A new study of recently married couples put a fresh take on their vows of “in sickness and in health,”
If there was ever any worry about the bacteria that could be transmitted during a couple’s kiss, a study of newlyweds in Iran found that their mental health issues could be impacted in the exchange as well.
Published in Exploratory Research and Hypothesis in Medicine, the 2025 study found that depression and anxiety can be transmitted from an affected partner to the other who previously showed no signs of mental issues. And the process could occur in just months.
“After six months, healthy spouses married to an insomniac with the depression-anxiety (DA) phenotype scored significantly higher on the Pittsburgh Sleep Quality Index, Beck Depression Inventory-II, and Beck Anxiety Inventory compared to their baseline scores,” the study found.
“This indicates that their sleep quality, depression, and anxiety scores became more similar to those of their affected spouses. Additionally, the composition of their oral microbiota changed significantly, becoming increasingly similar to that of their spouses,” it continued.
The stress hormone cortisol is triggered by anxiety or depression, and this affects the bacterial balance in the mouth.
“Specifically, in couples where one partner had [depression/anxiety], the oral microbiota of the healthy spouse mirrored that of the affected partner,” the researchers wrote.
The study was conducted with 268 newlywed Iranian couples, with one partner reportedly healthy and the other having sleep, depression and anxiety issues. Saliva samples and bacterial swabs revealed the presence of bacteria such as Clostridia, Veillonella, Bacillus and Lachnospiraceae.
“Salivary cortisol does not directly cause depression or anxiety but serves as an indicator of these disorders. The suggested mechanism of action is that the oral microbiota may directly compromise the blood-brain barrier or exert indirect effects through the oral microbiota-brain axis,” the researchers noted. “On the other hand, a diminished cortisol awakening response is linked to an increased likelihood of experiencing a negative and persistent progression of depression and/or anxiety disorders.”
They also found that ” the worsening of insomnia severity, an increase in salivary cortisol levels, and heightened depression and anxiety scores were more pronounced among female spouses after six months.”
The researchers acknowledged that there may have been underlying health issues and specific diet factors that they may not have verified in the evaluations.
“We suggest that these important variables should be fully considered in future studies,” they wrote.
“The transmission of oral microbiota plays a partial role in mediating depression and anxiety among couples. Since this study is associational, further research is needed to establish whether this association is causal,” they concluded. “If it is determined that this association is indeed causal, it could have significant implications for contemporary research. We propose that, within the framework of diagnostic, predictive, preventive, and personalized medicine, the practical and theoretical implications of this study may enhance our understanding of various aspects of microbiota-host interactions.”
The reactions on social media to the reported study were mixed.
„Yes, it is not my fault I’m depressed and anxious, it is yours!!”
— verata.sol 🇺🇸🇵🇱 (@veratadev) June 2, 2025
…. What?
— JD Sharp (@imjdsharp) June 2, 2025
You’re saying depression and anxiety is now a sexually transmitted disease
I guess that’s another reason I should just stay home, avoid people
And drink alone
In the dark
— Pat the Irishman (@Dad2Earthlings) June 2, 2025
The population-reduction agenda is so clear.
— Tom Löwe (@awaken_tom) June 2, 2025
I always trust studies from a credible country like Iran.
— Drunk Uncle (@DrunkUncle916) June 2, 2025
