The Gut and the Big Five Personality Traits

The Gut and the Big Five

The five-factor model is a framework to describe universal personality dimensions based on five dimensions (OCEAN): openness, conscientiousness, extraversion, agreeableness, and neuroticism.¹ It is estimated that personality is approximately 50 percent heritable-genetic with the balance of the contribution coming from social and environmental factors.²

The neuroticism dimension in particular has been linked to psychological vulnerability and a greater risk of morbidity and mortality.^3,4 A recent cross-sectional study of nearly 5000 individuals during the COVID epidemic found that neuroticism is positively correlated with anxiety and depression, but that metacognitive strategies are a better predictor of emotional well-being.⁵ In this post, we will evaluate yet another tool to influence trait neuroticism and help manage mental health challenges via the gut-brain axis.

Personality and the Gut Microbiome

Axel Bueckert/Dreamstime

In a recent observational study published in Brain, Behavior, and Immunity, investigators evaluated 672 adults (23 to 69 years of age) and found that the diversity and composition of the microbiome showed significant differences when stratified by the Big 5 personality traits.⁶ With regard to individuals who scored higher in the neuroticism trait specifically, the researchers found elevated levels of the bacterial class gammaproteobacteria which include a variety of genuses, including potential pathogens, such as Enterobacter, Escherichia, Haemophilus, Klebsiella, Pseudomonas, Shigella, and Vibrio. Elevations in these classes were also seen in individuals who scored low on the conscientiousness trait, which is associated with lower levels of motivation and self-discipline. The authors also identified HPA axis activation and elevated inflammatory markers in these higher neuroticism-lower conscientiousness individuals. Furthermore, it was noted that the increased gut barrier permeability which allows for bacterial translocation outside of the intestinal lumen, as well as the presence of circulating gram-negative bacterial lipopolysaccharide (LPS) toxins may play a role in the physiology of neuroticism.

A more recent study in the Human Microbiome Journal described the impact of gut microbes on personality traits via neural, immune, endocrine, and neurotransmitter pathways.⁷ The study included 655 adults with a mean age of 42 years (83 percent North American). The author found that increased anxiety and stress and decreased sleep quality were significantly associated with altered microbiome composition and reduced diversity, with particular bacterial genera associated with defined behavioral traits. For example, specific Bacteroides strains are associated with the production of the inhibitory neurotransmitter (GABA) important for warding off stressand depression.^8,9,10

Other findings of interest included the conclusion that a higher prevalence of Akkermansia and Lactococcus was associated with greater sociability and decreased Corynebacterium was associated with higher levels of neuroticism. Because this study evaluated diversity at the genus level, they did not find strong correlations between common probiotic species or strains and emphasized that the behavioral effects of these species have been found to be strain-specific.¹¹ Interestingly, however, although the author found a positive correlation between mental wellness and diets high in probiotic and prebiotic continuing foods, they did not find a similar correlation with individuals supplementing with pro- and prebiotic products.

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Seeding the Gut, Feeding the Mind

Why did the study find no positive correlations with the group taking supplemental probiotics compared with natural, food-based probiotics? The author suggests this may be the result of the fact that people with lower diversity and higher levels of gut disturbances are also those more likely to supplement, implying that the pre-existing conditions may have played a role in the findings. As mentioned by the author and elsewhere, strain-specific mechanisms play a significant role in efficacy.¹² Although the best approach to maintaining healthy gut diversity lies in a diverse, probiotic, and prebiotic-rich diet including whole foods, colorful vegetables and fruits, and fermented foods and beverages, careful selection of high-performance probiotic formulations can be helpful. Such brands are backed by clinical trials demonstrating increased microbial diversityand healthful post-biotic substance production such as the short-chain fatty acid butyrate.¹³

A number of commercially available brands are classified as psychobiotics. These have demonstrated clinical efficacy in improving mood, memory, and cognition–and potentially influencing Big 5 personality traits for the positive.¹⁴ But the buyer should beware. When evaluating a probiotic for gut-brain axis support, choose one with human clinical evidence on the final formulation, not just a single strain in a novel blend, to increase the likelihood you will experience the positive outcomes you seek.