Newlyweds’ anxiety, depression and insomnia levels become more similar due to sharing of oral bacteria, a new study has found.
The study measured the mental health of almost 1,750 couples before and after the first six months of marriage. Couples including one partner suffering with anxiety, depression and insomnia were compared to those including two unaffected partners.
Spouses married to an affected partner scored significantly higher on the Pittsburgh Sleep Quality Index, Beck Depression Inventory-II, and Beck Anxiety Inventory compared to their baseline. This means that their mental illness levels increased and became more similar to those of their spouses.
The composition of the newlyweds’ oral microbiomes also changed significantly after six months of marriage, becoming increasingly similar. In particular, the unaffected partner was found to take on the microbiota of their affected spouse.
High levels of Clostridia, Veillonella, Bacillus, and Lachnospiraceae bacteria were common in individuals suffering with depression, anxiety and insomnia. Increased levels of these bacteria were then noted in their spouses after six months. These changes correlated with increased levels of salivatory cortisol, a hormone associated with stress.
How do newlyweds transmit oral bacteria?
The makeup of the newlyweds’ oral microbiomes was measured by taking a swab of their tonsils and pharynx. The samples were collected first thing in the morning, prior to eating, drinking or any oral hygiene practices. This was repeated after 180 days and the composition compared.
The study determined that worsening mental illness scores and salivatory cortisol levels were more pronounced among female spouses than male. However in all groups, the mental illness scores remained much lower in spouses than their affected partner despite a significant increase.
The authors of the study suggest that oral bacteria transmission occurs through close contact in newlyweds. While they note that no studies have conclusively proved that this mechanism occurs, there is substantial evidence of similar types of bacterial exchange. For example, transmission of genital microbiota between partners.
It is also acknowledged that while the findings show an association between the microbiome and mental health, causation has not been proved. The authors said: ‘If it is determined that this association is indeed causal, it could have significant implications for contemporary research.’
The study was published in the Exploratory Research and Hypothesis in Medicine journal in May.
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