Researchers Say Kissing Can Transmit Depression and Anxiety

The hypothesis is that when someone is suffering from psychological distress, their stress hormones like cortisol can alter their oral microbiota. When they kiss their partner, these altered microbial communities may be transferred through saliva, potentially disrupting the partner's own microbiota. This could, in turn, impact their brain-gut axis—the biochemical signaling that takes place between the gastrointestinal tract and the central nervous system—and possibly trigger mental health symptoms. While this chain of causation is still under investigation, it opens a new frontier in understanding how closely physical and mental health are linked in intimate relationships.