Irish scientists from University College Cork found that transplanting a community of bacteria (microbiota) from the guts of people with social anxiety disorder into laboratory mice made the rodents more anxious. The study was published in the scientific journal magazine Neuroscience.
Social anxiety disorder, also known as social phobia, is a mental health condition characterized by an intense fear of social situations in which people feel extremely self-conscious, out of place, and embarrassed, leading to avoidance of social interactions.
The recent discovery of the microbiota-gut-brain axis, a complex, bidirectional communication network between the gut microbiota and the brain, has highlighted the potential impact of gut microorganisms on a variety of psychological and mental health problems.
The study included six participants diagnosed with social anxiety disorder and six healthy adults with no history of mental illness. The recipients of the transplants were 72 male mice who were eight weeks old at the start of the experiment.
After acclimation, the researchers treated the mice with a powerful antibiotic cocktail including ampicillin, vancomycin, imipenem, and neomycin in their drinking water. This combination destroyed the mice’s natural gut microbiota, preparing them for transplantation of human microbiota. Each mouse received the gut microbiota from a randomly selected human participant.
Ten days after the procedure, the researchers performed a series of behavioral tests as well as extensive biochemical analysis and collected fecal samples from the mice before and after transplantation.
Behavioral tests showed that mice receiving gut microbiota from participants with social anxiety disorder experienced reduced social interaction. However, their antisocial behavior did not change. This led the researchers to conclude that sensitivity to social fear was increased in these mice.
Further analysis showed that these mice had reduced levels of the hormone corticosterone. Corticosterone is a steroid hormone produced by the adrenal cortex and primarily involved in the regulation of stress reactions, energy metabolism, immune responses, and electrolyte balance in the body.
According to scientists, further research has allowed us to better understand the functioning of the microbiota-gut-brain axis and develop new treatments for social phobia.
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