The human gut tells us a lot about our health – but what about our personality?
Dr. Katerina Johnson of Oxford University’s Department of Experimental Psychology has been researching the relationship between the bacteria living in the gut (microbiome) and behavioral traits. Her research revealed that both gut microbiome composition and diversity were related to differences in personality (Johnson, K., 2020). Interestingly, the study also found that sociable people have higher levels of certain types of bacteria in their gut.
In this article, we take a deep-dive into the “gut-brain” connection to health and mood, and what this Oxford study means for both microbiome and personality research. We also look at how this study could lead to better treatments for mental health disorders such as depression and where the potential $942 million human microbiome market is headed.
The Gut-Brain Connection
Within walls of the digestive system, there is a “second brain” in our gut that is helping researchers understand the links between digestion, mood, and health. According to Johns Hopkins Medicine, “scientists call this little brain the enteric nervous system (ENS). The ENS is two thin layers of over 100 million nerve cells lining your gastrointestinal tract from the esophagus to the rectum (Johns Hopkins). Researchers and physicians once thought that anxiety and depression contributed to gut health and issues such as irritable bowel syndrome (IBS). But several studies have now shown evidence to the contrary, revealing that irritation in the gastrointestinal system may send signals to the central nervous system (CNS) that trigger mood changes.
Jay Pasricha, M.D., director of the Johns Hopkins Center for Neurogastroenterology, states, “These new findings may explain why a higher-than-normal percentage of people with IBS and functional bowel problems develop depression and anxiety (Johns Hopkins).” These critical findings led to further breakthrough studies, including those on the microbiome and autism.
Microbiome Studies and Next-Level Research
With the rise in autism and the frustration of ineffective treatment, Arizona State University researchers decided to take microbiome research to the next level by performing a fecal transplant technique known as microbiota transfer therapy on children with Autism Spectrum Disorder (ASD).
Roughly 30-50% of all people with autism have chronic gastrointestinal problems that can last for many years. These issues cause irritability, decreased attention and learning, and negatively impact behavior (Science Daily, 2019). After the transplant, parents reported a steady reduction of ASD symptoms during treatment and over the next two years. They also found a 45% reduction in core ASD symptoms (language, social interaction, and behavior) at two years post-treatment. The study proved that by transferring healthy microbiota to individuals lacking certain gut bacteria, it is possible to donate a more diverse set of bacteria into the patient and improve gut health (Science Daily, 2019).
The Oxford Study
Dr. Johnson’s research at Oxford University found that numerous types of bacteria that had been linked with autism in previous research were also related to differences in sociability in people. She reveals, “This link suggests that the gut microbiome may contribute not only to the extreme behavioral traits seen in autism but also to variation in social behavior in the general population (University of Oxford, 2020).” Johnson’s study involved 671 adults to submit a fecal sample and complete a questionnaire assessing their diet, behavior, health, lifestyle, and social demographics. Analyses was conducted to determine the relationships between gut microbiome composition and the study variables, with a particular interest in personality traits.
Before Johnson’s findings, only animal or clinical population studies have demonstrated that the gut microbiome can influence the stress response, anxiety, and depressive-like behaviors, as well as personality and communication (Johnson, K., 2020). In her study, both gut microbiome composition and diversity were found to be related to differences in personality. Additional results revealed:
- Abundances of specific genera are related to behavioral traits, suggesting that studying the gut microbiome may be a critical factor in understanding variation in human personality.
- Social people were found to have more diverse microbial communities, indicating that social behavior may promote diversity in the microbiome.
- In contrast, lower diversity was associated with increased levels of anxiety, and these traits were also related to differences in overall composition of the microbial community.
- People who ate more foods with naturally occurring probiotics or prebiotics had significantly lower levels of anxiety, stress, and neuroticism and were less likely to suffer from mental health disorders (Johnson, K., 2020).
A New Frontier in Mental Health Treatment
Johnson did add that since this is a cross-sectional study, future work will benefit from researching the potential effect these bacteria may have on behavior, which may help inform the development of new therapies for depression. Researchers are now looking into microbial functioning to gain a deeper understanding of the gut in people with mental health disorders. Dr. Premysl Bercik, a gastroenterologist at Hamilton Health Sciences in Canada has been doing extensive work in the microbiota gut-brain area and is presenting at the 2020 International Human Microbiome Consortium Congress (IHMC) on the “Investigation of the Gut Microbiome in Patients with Mental Health Disorders.” His most recent published work focused on how probiotics can improve symptoms of depression.
Personality can influence our relationships, stress levels, and even the careers we choose. The Oxford study is a revealing look at how the gut affects our body’s physiology, digestion, development, and now – even our behavior. Knowing the potential links between the gut and behavior provides useful insights toward developing and testing personality and microbiota-based interventions for promoting better health.
References:
Johns Hopkins Medicine (n.a, n.d.). The gut-brain connection. Retrieved from https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-brain-gut-connection.
Johnson, K. (2020). Gut microbiome composition and diversity are related to human personality traits. Human Microbiome Journal. Vol. 15. 100069.
Science Daily (2019). Autism symptoms reduced nearly 50 percent two years after fecal transplant. Retrieved from https://www.sciencedaily.com/releases/2019/04/190409093725.htm.
University of Oxford (2020, January 23). Gut bacteria linked to personality. Retrieved from http://www.ox.ac.uk/news/2020-01-23-gut-bacteria-linked-personality.