Family Dogs May Improve Adolescent Mental Health by Shaping the Microbiome, New Study Suggests
Growing up with a family dog may do more than provide companionship and emotional comfort. According to new research published in the scientific journal iScience, living with dogs during adolescence is linked to better mental health, fewer social problems, and measurable changes in the human microbiome. The study suggests that these benefits may be partly explained by how dogs influence the community of microbes living in and on our bodies, particularly those connected to the gut–brain axis.
The research was conducted by a team led by Takefumi Kikusui at Azabu University in Japan, building on years of work exploring how animals influence human development. Previous studies had already shown that children who grow up with dogs often report higher levels of social support, companionship, and emotional well-being later in life. Separately, scientists have found that dog owners tend to have more diverse microbial communities compared to people without pets. This new study brings those two lines of research together in a more direct and experimental way.
How Dog Ownership Was Linked to Teen Mental Health
The researchers focused on adolescents around the age of 13, a critical developmental period marked by emotional, social, and psychological changes. Using standardized behavioral and mental health assessments, they compared teens who lived with dogs to those who did not.
The results were consistent and notable. Adolescents who had a dog at home showed lower levels of social problems, including fewer difficulties with peer relationships and reduced behavioral challenges. Measures related to emotional well-being were also higher among dog-owning teens. Importantly, the researchers found that dog ownership at age 13 could predict mental health outcomes one year later, suggesting that the relationship was not simply a short-term effect.
Rather than framing dogs as a cure-all, the study carefully points out that dog ownership appears to be one contributing factor among many that influence adolescent mental health. Still, the association was strong enough to prompt deeper investigation into possible biological mechanisms behind the effect.
What the Microbiome Has to Do With Mental Well-Being
To explore the biological side of the relationship, the researchers examined the oral microbiome of the participating adolescents. Microbiomes are collections of bacteria, fungi, and other microorganisms that live in different parts of the body, including the mouth, skin, and gut.
Interestingly, the overall diversity and richness of microbes were similar between teens with dogs and those without. However, the composition of the microbiome differed. Certain bacterial groups were more or less abundant depending on whether a teen lived with a dog. This distinction is important because changes in microbial balance, even without changes in diversity, can have meaningful effects on health.
The research team hypothesized that some of these microbial differences might be linked to psychological traits and behaviors. This idea is rooted in growing evidence around the gut–brain axis, a communication network connecting the nervous system, immune system, and microbiota. Through this axis, microbes can influence brain chemistry, stress responses, and social behavior.
Testing the Theory Using Animal Models
To test whether the microbiome itself could influence behavior, the researchers conducted an additional experiment using laboratory mice. Microbiota collected from dog-owning adolescents were transplanted into mice and compared with mice that received microbiota from non-dog-owning teens.
The behavioral differences were striking. Mice that received microbiota from dog-owning adolescents spent more time sniffing and interacting with their cage mates, a common indicator of social interest in animal research. They also showed a greater tendency to approach and interact with a trapped cage mate, a standard test used to measure prosocial or empathy-like behavior in rodents.
These findings suggest that specific bacteria associated with dog ownership may promote social behaviors, at least in animal models. While mouse behavior cannot be directly equated with human psychology, such experiments are a key tool for understanding potential biological pathways.
Why Dogs Might Change the Human Microbiome
Living with a dog naturally increases exposure to a wider range of microbes. Dogs spend time outdoors, interact with soil, plants, and other animals, and then bring those microbes into the household. Close contact, such as petting, playing, and shared living spaces, allows for microbial exchange between dogs and humans.
Over time, this exposure may help shape a more balanced or resilient microbiome, particularly during childhood and adolescence when microbial communities are still developing. The researchers suggest that this process of symbiosis between humans, dogs, and microorganisms could be one reason dogs have such a consistent positive presence in human lives.
The Role of the Gut–Brain Axis
The gut–brain axis has become a major focus of mental health research in recent years. Microbes can influence the production of neurotransmitters, regulate inflammation, and affect stress hormones. All of these factors play roles in mood, anxiety, and social behavior.
In adolescents, whose brains are still undergoing significant development, these microbial signals may be especially influential. The study adds evidence that environmental factors, such as pet ownership, can shape mental health through biological pathways rather than social interaction alone.
Long-Term and Evolutionary Perspectives
The researchers note that humans and dogs have lived together for tens of thousands of years. This long history of coexistence may have allowed subtle biological relationships to form over generations. While modern lifestyles differ greatly from those of early humans, the fundamental human–dog bond remains strong.
The study also raises questions about whether early-life exposure to dogs could have long-term mental health benefits, extending into adulthood. Although more longitudinal research is needed, the findings suggest that the effects of dog ownership may go beyond childhood companionship.
Important Limitations to Keep in Mind
Despite its strengths, the study does not claim that dogs directly cause better mental health outcomes. Human data remain correlational, meaning other factors such as family environment, physical activity, and socioeconomic conditions could also contribute.
Additionally, not every child or family is in a position to own a dog, and dog ownership comes with responsibilities that may not be suitable for everyone. The researchers emphasize that dogs should not be viewed as a medical intervention, but rather as a potentially beneficial environmental influence.
What This Study Adds to the Bigger Picture
This research stands out because it connects behavioral data, microbiome analysis, and experimental animal testing in a single framework. It strengthens the idea that mental health is shaped by a complex interaction of social experiences, biology, and environment.
For parents, educators, and researchers, the findings highlight how everyday aspects of life, such as living with a pet, may quietly influence psychological development in meaningful ways.
Research paper reference:
https://www.cell.com/iscience/fulltext/S2589-0042(25)02209-6
