Mental health issues such as anxiety, depression, and insomnia can be transmitted through intimate contact between partners. A recent study found that couples where one partner had mental health problems were more likely to "infect" their healthy spouse with similar bacteria in their mouth microbiome.
The study discovered that formerly healthy spouses exhibited higher scores for depression, anxiety, and insomnia after six months, with increased levels of cortisol. The researchers used DNA sequencing techniques to examine the mouth bacteria of both partners before and after this period. This suggests that the bacteria exchanged through kissing may be mediating these mental health issues.
The World Health Organization estimates that over 300 million people worldwide suffer from depression, with pandemic-era stressors increasing rates by up to 25 percent.