New research suggests that depression and anxiety may be contagious between spouses, not just emotionally, but biologically, through oral bacteria.
A groundbreaking study led by Iranian researcher Reza Rastmanesh suggests depression and anxiety might be biologically transmissible between spouses via oral bacteria.
The study, conducted with 268 newlywed couples in Tehran, found that healthy partners of individuals with depression and insomnia developed elevated anxiety, mood disturbances, and altered oral microbiota over six months.
“Oral microbiota transmission between individuals in close contact partially mediates symptoms of depression and anxiety,” the study noted.
Researchers identified increases in bacterial groups such as Clostridia and Veillonella—microbes previously associated with mental illness. Women showed higher vulnerability, with cortisol levels nearly doubling.
The findings support a growing theory that emotional states may synchronize through microbial and hormonal pathways in close relationships.
While preliminary, the research opens new avenues for holistic mental health care. “Fecal microbiota-induced insomnia and depression-like behaviors in mice can be alleviated by microbiota-modulating probiotics,” researchers added, hinting at future interventions.