Gut Bacteria May Be Linked to Personality, New reaerch Suggest

New research reveals fascinating correlations, such as sociability and neuroticism, between gut bacterial diversity and personality traits. The findings also draw attention to the potential benefits of pre- and probiotic rich consuming foods.

New research suggests that a person’s gut bacteria may be programmed to demonstrate how nervous or sociable they are.

Katerina Johnson, Ph.D. from Oxford University’s Department of Experimental Psychology, United Kingdom, set out to examine whether there was a connection between the composition of the gut bacteria and personality traits such as sociability and neuroticism.

She explains the motivation for her research, saying, “Research has been growing that links the gut microbiome to the brain and behaviour, known as the microbiome-good-brain axis.”

“Most research has been done in animals, while studies in humans have focused on the role of the gut microbiome in neuropsychiatric conditions.”

“In comparison, my main interest was to look at the general population to see how personality-related variability in the types of bacteria living in the gut can be.”

To this end, Johnson gathered fecal samples from 655 individuals, 71 per cent of whom were female and 29 per cent were male, with an average age of 42. The scientists used sequencing analysis of the 16S rRNA gene to analyze abundances of different bacterial genera.

The study involved asking participants to respond to a comprehensive survey questionnaire inquiring about their behavior, health, lifestyle, and sociodemographic factors.

Johnson conducted a set of statistical analyzes that helped determine the relationship between the gut bacteria composition and behavioral traits like sociability and neuroticism.

The scientist published her findings in the Journal of Human Microbiome.

Gut bacteria and five personality traits

More specifically, the researcher used the International Personality Item Pool— which consists of 50 items— to evaluate personality traits based on the “five-factor personality model.”

This model suggests that personality differences are grouped into five main fields, or the “Big Five:”

  • extraversion, or the “propensity to seek and enjoy others’ company”
  • agreeableness, defined as “trust and cooperation in social interactions”
  • conscientiousness, or the “attention to detail and focus”
  • neuroticism, i.e., the “tendency to feel negative emotions”
  • openness, which researchers have described as “creativity, intellectual curiosity, and willingness to seek new experiences”

Johnson applied multiple bacterial taxa regression analyzes and adjusted key variables that scientists know influences the gut bacteria’s composition, and that might have confused the results otherwise.

These variables included sex, age, body mass index (BMI), mode of delivery of births, method of feeding infants, use of oral antibiotics in the last 6 months, gut conditions and use of probiotic supplementation.

For these potential confounders Johnson adjusted only in a subset of 261 participants who had provided the necessary information.

More friends may promote gut health

The study revealed that various types of bacteria that had been related in past studies by researchers to autism spectrum disorder also had associations with variations in sociability in the general population.

“This indicates that the gut microbiome will contribute not only to the severe behavioral traits seen in autism but also to variability in the general population’s social behaviour,” states the author of the study.

In addition, the study found that individuals with broader social networks were more likely to have a more diverse gut bacteria composition. This suggests that being socially active can foster gut microbiome diversity, the author writes.

Many people believe that increased diversity in the human gut microbiome promotes wellness in the gut and improves overall health.

“This is the first study to find a link between sociability and microbiome diversity in humans and follows on from similar findings in primates, which have shown that social interactions can promote gut microbiome diversity. This result suggests the same may also be true in human populations.”

– Katerina Johnson

In comparison, the analysis revealed the correlation of lower microbial diversity with higher levels of stress and anxiety.

The importance of nutrition

In fact, an intercorrelation study “revealed that people who ate more foods with naturally occurring probiotics or prebiotics had significantly lower levels of anxiety, stress and neuroticism and were also less likely to develop a mental illness.”

Furthermore, the researcher did not find the same association for probiotics or prebiotics in supplementary form.

Natural probiotic sources include fermented cheese, sauerkraut, kimchi, and natural prebiotic sources include bananas, legumes, whole grains, asparagus, cabbage, and leek.

Another intriguing finding was that there was a less diverse gut microbiome among those who had been fed formula as infants.

“This is the first time that this has been studied in adults and the results suggest that child feeding can have long-term effects on gut health,” Johnson says.

“Our modern-day living can provide a perfect storm for intestinal dysbiosis[ i.e., an imbalance in the microbiota],” Johnson adds.

“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.”

– Katerina Johnson

“All these factors can influence the gut microbiome, and so our behavior and psychological well-being can be affected in currently unknown ways.”

However, the scientist also recognizes a limitation of her research. She says, “Since this is a cross-sectional study, future research may benefit from directly investigating the potential behavioral effects these bacteria may have, which may help inform the development of new autism and depression therapies.”

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