Study Links Dog Ownership in Adolescence to Improved Mental Health and Microbiome Changes
New study finds adolescents with dogs have better mental health and distinct microbiomes, with mouse experiments suggesting bacteria play a role in social behavior.
ERBIL (Kurdistan24) — Adolescents who own dogs exhibit fewer behavioral problems and distinct changes in their microbiome compared to their peers without pets, according to new research published Thursday in the journal iScience. The study suggests that the bacteria exchanged between humans and canines may play a biological role in supporting social well-being during critical developmental years.
Led by researchers at Azabu University and Gunma University in Japan, the study utilized data from the Tokyo Teen Cohort to examine the relationship between pet ownership, mental health, and the composition of the oral microbiota. The research team analyzed data from 345 participants who were followed from age 13 to 14.
According to the findings, adolescents who owned dogs demonstrated significantly better mental health outcomes than those who did not. Specifically, dog owners scored lower on the Child Behavior Checklist (CBCL), a standardized measure where lower scores indicate fewer issues. The researchers reported that the most significant difference was found in the category of "social problems," though dog owners also showed lower scores for "social withdrawal," "thought problems," "delinquent behavior," and "aggressive behavior."
Beyond psychological assessments, the study investigated biological mechanisms by analyzing saliva samples from the participants. While the overall diversity of the microbial community remained similar between the two groups, the composition differed. The analysis revealed that specific bacterial genera, including Streptococcus, Neisseria, and Prevotella 7, showed differential abundances. Notably, twelve genera were significantly less abundant in the saliva of non-dog owners.
To determine if these microbial differences could directly influence behavior, the researchers conducted experiments using germ-free mice. They transplanted saliva from the adolescent participants into the mice and observed the animals' subsequent social interactions.
The study reported that mice receiving microbiota from dog-owning adolescents displayed higher levels of social behavior compared to those receiving samples from non-owners. These behaviors included increased "anogenital sniffing" and a greater willingness to approach a "trapped" mouse—a test used to measure social interest.
The researchers identified specific Amplicon Sequence Variants (ASVs) belonging to the genus Streptococcus that correlated with these behavioral outcomes. In the human subjects, specific Streptococcus ASVs were negatively associated with thought problems and delinquent behaviors. In the mouse models, similar bacterial variants were strongly associated with increased social approach behaviors.
"These results suggest that microbiota may be partly involved in improving the well-being of adolescents living with dogs," the authors wrote. They hypothesized that the shared living environment facilitates the transfer of bacteria between dogs and their owners, potentially influencing the "gut-brain axis," a communication network linking the emotional and cognitive centers of the brain with intestinal functions.
The paper, authored by Eiji Miyauchi, Takefumi Kikusui, and colleagues, notes that adolescence is a critical period for neurobehavioral development, characterized by significant changes in the brain's prefrontal cortex and limbic system. While previous studies have established a link between pet ownership and reduced stress, this research provides experimental evidence involving the microbiome.
The authors acknowledged several limitations to the study. The cohort was based in the Tokyo metropolitan area, which may limit generalizability due to socioeconomic factors. Additionally, while the human analysis used saliva samples, the mouse analysis relied on fecal samples, making direct comparison difficult, though Streptococcus was dominant in both.
The research was supported by the JST-Mirai Program and other Japanese academic grants. The findings indicate that the benefits of dog ownership may extend beyond simple companionship, involving complex biological interactions that shape social development.