Owning a dog can significantly enhance the mental health and social behaviour of teenagers, according to new scientific research that suggests sharing microbes with a canine companion could be a key factor.
The Study: Linking Dogs, Teens and Microbes
Scientists from Japan's Azabu University, led by Professor Takefumi Kikusui, analysed data from 343 healthy adolescents taking part in the Tokyo Teenager Cohort Study. Of this group, 96 were dog owners.
The research, published in the journal iScience, found that by the age of 14, teenagers who had owned a dog at 13 scored markedly lower for a range of issues. These included social problems, social withdrawal, thought problems, delinquent behaviour, and aggressive behaviour compared to their peers without dogs.
The Microbiome Connection
Intriguingly, the study delved deeper to explore a potential biological mechanism. Analysis of the teenagers' saliva revealed that while microbiomes were broadly similar, 12 types of bacteria – including Streptococcus and Prevotella – were significantly less abundant in those who did not own a dog.
To test the influence of these microbes, the team transplanted saliva samples from the teenagers into germ-free mice. The results were telling: mice receiving microbes from dog-owning adolescents displayed more "preconcern" or empathetic behaviour, such as sniffing unfamiliar mice and approaching trapped cage-mates.
"Several studies have reported the mental health benefits of dog ownership, and we have demonstrated that the microbiome may be one mechanism involved," said Professor Kikusui. The team noted that certain gut bacteria in the mice were linked to their social behaviour, with some strains also associated with the teenagers' own conduct.
Cautions and Considerations
The researchers were careful to note the study's limitations. Professor Stefan Reber of Ulm University, who was not involved in the work, pointed out it only shows a correlation between dog ownership and a different salivary microbiome in teens.
Kikusui agreed, stating it remains unclear if the microbial differences come directly from the dogs or from the stress-reducing effects of pet ownership, which in turn alters microbiota. He also emphasised that the findings do not mean everyone should rush to get a dog.
"Even without owning a dog, maintaining a diverse microbiome can potentially improve mental health scores," he noted. Furthermore, for some, dog ownership can be stressful, particularly if the animal has behavioural issues.
The study opens a fascinating new avenue in understanding the complex, health-boosting bond between humans and their pets, suggesting the benefits may be written in part in our bacteria.
