A study suggests that owning a dog can change the human microbiome in ways that promote empathetic and social behaviors. Researchers found that adolescents with dogs exhibit less social withdrawal and aggression, linked to specific bacteria. Experiments in mice confirmed these microbes enhance prosocial traits.
Takefumi Kikusui at Azabu University in Japan investigated how dogs might influence well-being beyond companionship by altering the gut microbiome. Pets are known to improve life satisfaction and shape microbial communities, which in turn affect mental health and personality traits. Dogs, as popular pets, were the focus of this research published in iScience (DOI: 10.1016/j.isci.2025.113948).
The study surveyed caregivers of 343 adolescents aged 12 to 14 in Tokyo, where about one-third had a pet dog. Dog owners scored lower on social withdrawal and aggression, even after adjusting for factors like sex and household income. Saliva analysis showed higher levels of Streptococcus bacteria in these adolescents, a species associated with reduced depressive symptoms.
Gerard Clarke at University College Cork in Dublin, Ireland, explained the mechanism: “If you’re playing with a dog a lot, you’re going to have a lot of exposures to the microbes the dog has, from licks [and] them jumping up on you.” These microbes reach the gut and produce anti-inflammatory short-chain fatty acids that support mental health.
To test causality, researchers transplanted oral microbes from three dog owners and three non-owners into germ-free mice. Over weeks, behavioral tests revealed differences. In an empathy trial, mice receiving dog-owner microbes chewed and poked at a tube trapping another mouse more frequently, indicating attempts to help—behavior aligned with recent findings on mouse caregiving, such as aiding births or providing first aid.
Socially, these mice sniffed unfamiliar companions more often. Clarke noted, “These social behaviours are relevant across species, including humans. Social networks are a positive thing for mental health – if you have low exposure to social networks, or if your social network is small, then that probably isn’t a good thing.”
Future probiotics could replicate these effects for non-dog owners, though studies in diverse locations are needed due to varying microbial exposures.