A new study suggests that the beneficial effects of dogs on human mental health may be partly due to the exchange of microorganisms.
Researchers writing in the journal iScience reported that dog ownership leads to an increase in the microbes on and within owners' bodies that are linked to mental well-being, according to Reuters.
Previous studies have found that people who grow up with dogs and continue to own them later in life score higher on measures of empathy and a need for social support.
Other studies have shown that dog owners have differences in the community of beneficial microorganisms living in their gut, known as the gut microbiome, compared to those who do not own dogs.
In the new study, researchers analyzed oral microbiome samples collected from 13-year-olds who owned dogs and those who did not. They found similar diversity and richness in the types of microorganisms between the two groups. But the microbiome structure contained variations, suggesting that dog ownership altered the abundance of certain oral bacteria.
When researchers treated mice with the microbiome of dog-owning teenagers to see if and how this would affect their social behavior, they found that the mice that received the dog-owning microbiome spent more time socializing with their peers and exhibited more “pro-social behavior.”
“The most interesting finding of this study is that bacteria that promote pro-social behavior, or empathy, were discovered in the microbiome of children who own dogs,” said study director Takefumi Kikusui of Azabu University in Japan in a statement.
The study authors say that while more research is needed, the findings suggest that having a dog in the home can alter the microbiome in ways that support mental health, empathy, and pro-social behavior.