New UCC research discovers link between social anxiety disorder and gut microbes

NEW RESEARCH LED by a University College Cork professor has discovered possible links between microbes in our guts and social anxiety disorder (SAD).

Social anxiety disorder is a long-term and overwhelming fear of social situations.

It usually starts in teenage years and while for some people it gets better as they get older, many others require treatment.

The new study, published in Proceedings of the National Academy of Sciences (PNAS), builds on recent findings that SAD patients have distinct microbiomes when compared with healthy individuals.

Gut microbiota is the system of microorganisms in a person’s gastrointestinal system.

The latest research transplanted microbiota from six patients with SAD into mice and this resulted in the mice exhibiting increased sensitivity to fear conditioning during social interactions, as well as changes to immune and brain functions.

The research APC and UCC’s vice president for research and innovation Professor John F. Cryan.

APC Microbiome Ireland is based in UCC and Teagasc and is a world-leading research centre focused on understanding the gastrointestinal bacterial community and harnessing the power of microbiota for the health and wellbeing of people and the planet.

Commenting on the research, he said: “SAD is an increasing issue for the human population, so it is vital to explore new treatments to address the condition.

“Discovering a link between the microbiota and the SAD condition is a significant breakthrough that the microbiota represent potentially a therapeutic target.”

SAD is one of the most disabling anxiety disorders and the new research shows that gut microbiota may be a target for new treatment strategies to be developed.

Although the mice that received the SAD microbiota had normal behaviours across a range of tests designed to assess depression and general anxiety-like behaviours, they had a heightened sensitivity to social fear.

The work could demonstrate a “interkingdom” basis for social fear responses (hormonal communication between microorganisms and their hosts has been dubbed “interkingdom signalling).

The team took faecal samples from six healthy people and six people with SAD, and after DNA analysis confirmed the gut microbes were significantly different, they were transferred into 72 mice.

The mice were then presented with a series of tests to examine their anxiety and social fear.

To examine social fear, mice were given small electric shocks when they approached a new mouse.

The research team then observed how the animals behaved around new mice when the electric shocks were no longer applied.

While mice with gut microbes from healthy people quickly regained their social interaction time with new mice in the days that followed, those with microbes from people with SAD continued to be fearful of approaching other mice.

Mice that received the SAD microbiota also had alterations in brain oxytocin levels and central and peripheral immunity.

Oxytocin intensifies the experience of both positive and negative social interactions and governs social behaviour.

The paper’s author’s say the findings show that “the microbiota–gut–brain axis is an ideal target for identifying novel therapeutics to improve symptoms in SAD”.