Researchers from University College Cork explored how a community of gut bacteria from people with social anxiety disorder could influence behavior when transplanted into laboratory mice. The study, published in a Neuroscience journal, examined whether human gut microbiota could modify anxiety-related traits in animals and shed light on connections between the gut and the brain.
Social anxiety disorder, sometimes called social phobia, is a mental health condition marked by intense fear in social situations. People with this condition often feel highly self conscious, out of place, and embarrassed, which can lead to avoidance of social interactions.
The modern discovery of the microbiota-gut-brain axis describes a bidirectional communication system linking gut microorganisms with brain function. This framework has prompted researchers to investigate how gut microbes might influence a range of psychological and mental health outcomes.
The experiment included six adults diagnosed with social anxiety disorder and six healthy adults without a history of mental illness. From these participants, gut microbiota samples were prepared for transplantation into a group of mice. A total of 72 eight-week-old male mice served as recipients in the study.
Before transplantation, the mice underwent an acclimation period. They were then given a powerful antibiotic cocktail in their drinking water, comprising ampicillin, vancomycin, imipenem, and neomycin. This combination effectively suppressed the mice’s native gut microbiota, creating an opportunity for the human microbiota to establish itself in the gut environment. Each mouse received a microbiota sample from a randomly selected human donor.
Ten days after the transplant, researchers conducted behavioral assessments and carried out extensive biochemical analyses, including collecting fecal samples before and after the microbiota transfer. The results showed that mice receiving microbiota from donors with social anxiety disorder displayed reduced social interaction. Their antisocial tendencies did not show a parallel change. The observation suggested heightened sensitivity to social fear in these animals.
Biochemical analyses revealed lower circulating levels of corticosterone in the mice that received microbiota from anxious donors. Corticosterone is a steroid hormone produced by the adrenal cortex and plays a role in stress responses, energy regulation, immune function, and electrolyte balance. These findings imply a link between gut microbial composition and stress hormone regulation in this context.
The researchers noted that this line of inquiry advances understanding of the microbiota-gut-brain axis and could inform the development of novel strategies for addressing social anxiety symptoms. Additional work is needed to determine the reliability and scope of these effects, including replication in larger studies and exploration of potential therapeutic implications for humans.
Earlier studies have also investigated connections between gut bacteria and body weight regulation, highlighting the broader significance of microbial communities for health and behavior across multiple domains.