In a recent study published in Exploratory Research and Hypothesis in Medicine, Iranian scientists followed 268 newlywed couples.
Participants completed surveys about their mental health and provided saliva samples for cortisol measurement and oral bacteria swabs for DNA analysis.
When one partner reported depression, anxiety and insomnia, the other partner, who previously had no symptoms, started showing similar symptoms after six months.
Researchers found that their oral bacteria also changed due to the stress hormone cortisol.
Researchers believe that close contact, including kissing, can transmit disrupted microbiomes from one person to another.
However, this doesn’t mean that kissing causes depression. It does suggest that mental health symptoms can transfer to people closest to you in ways not completely understood.
Researchers say more work is needed to understand how microbiomes behave and if they play a role in other conditions like PTSD, bipolar disorder and chronic fatigue.
Another caveat of the study is that it did not control all aspects. Diet, lifestyle factors and other underlying conditions were not taken into consideration.
