Gut bacteria linked to social behavior, study finds

Gut microbiome composition and diversity are related to differences in personality, including sociability and neuroticism, according to new research published in the Human Microbiome Journal.

There has been growing research linking the gut microbiome to the brain and behavior. Most research has been conducted in animals, while studies in humans have focused on the role of the gut microbiome in neuropsychiatric conditions.

In the current study, researchers led by Katerina Johnson, PhD, from the University of Oxford in England looked at the general population to see how variation in the types of bacteria living in the gut may be related to personality.

Previous studies have linked the gut microbiome to autism, a condition characterized by impaired social behavior. The study found that numerous types of bacteria that had been associated with autism in previous research were also related to differences in sociability in the general population. This suggests that the gut microbiome may contribute not only to the extreme behavioral traits seen in autism but also to variation in social behavior, said Johnson.

The study found that people with larger social networks tended to have a more diverse gut microbiome, which is often associated with better gut health and general health. The researchers also found that adults who had been formula-fed as children had a less diverse microbiome in adulthood.

Diversity was also positively related to international travel, perhaps due to exposure to novel microbes and different diets. More adventurous eaters had a more diverse gut microbiome while those on a dairy-free diet had lower diversity. Furthermore, diversity was greater in people with a diet high in natural sources of probiotics, such as fermented cheese, sauerkraut, and kimchi, and prebiotics, such as banana, legumes, whole grains, asparagus, onion, and leek, but notably not when taken in supplement form.

Johnson said since this is a cross-sectional study, future research may benefit from directly investigating the potential effect these bacteria may have on behavior, which may help inform the development of new therapies for autism and depression.

"Our modern-day living may provide a perfect storm for dysbiosis of the gut,” said Johnson in a statement. “We lead stressful lives with fewer social interactions, and less time spent with nature, our diets are typically deficient in fiber, we inhabit over-sanitized environments and are dependent on antibiotic treatments. All these factors can influence the gut microbiome and so may be affecting our behavior and psychological well-being in currently unknown ways."