Generally, personality refers to the characteristics responsible for the relatively consistent patterns of thinking, feeling and behaviour of a person. The Five-Factor Model of personality, described by Costa and McCrae (2000), includes five dimensions of personality: Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness.

Neuroticism refers to the tendency to experience negative emotional states and to emotional instability. High values relate to emotional suffering, anxiety, depression and panic, while low values relate to less anxious states and to less reactive, more emotionally stable individuals.

Extraversion refers to the way we socialize. High values are associated with warm, sociable, friendly people with a higher tendency to experience positive emotions, whereas low values relate to a bigger tendency to isolate and be less comfortable in situations involving socialization. Openness refers to the tendency to experience new things and take interest in a lot of subjects. People with higher scores tend to be more creative, to value feelings and beauty, to be more curious and have a tendency to re-evaluate social norms. Individuals with lower scores, on the other hand, tend to be more traditional and conventional. Agreeableness refers to the quality of interpersonal relationships. High values reflect friendly, optimistic and empathetic individuals, whereas low values reflect increased aggressiveness, hostility and a bigger tendency to be critical of others. Conscientiousness is related to control, organization and perseverance. People with high scores tend to be organized, hard-working, diligent and cautious. People with low scores tend to be impulsive and disorganized.

Differences in personality are associated with distinct brain function. Since bacteria in the gut can communicate with the brain through the gut-brain axis, it can be hypothesized that the microbiome might be linked to differences in personality.

In this context, a study published in march of 2018 in the “Brain, Behavior, and Immunity” journal took the first steps to study this hypothesis. The researchers recruited a group of 672 South-Korean adults between the ages of 23 and 69. Faecal samples were collected and bacterial DNA was extracted, amplified and sequenced to assess the gut microbiome. Personality traits were assessed using the Korean version of the Revised NEO Personality Inventory (NEO PI-R).

The authors found that the gut microbiome of individuals with high scores in Openness was richer and more diverse than the microbiome of individuals with low scores. Higher Agreeableness also corresponded to higher alpha-diversity (mean species diversity in a specific habitat).

But the more significant correlations reported related to Neuroticism and Conscientiousness. High Neuroticism was correlated with an increased abundance of bacteria of the class Gammaproteobacteria and the order Pasteurellales. The phylum Proteobacteria was significantly increased in the low Conscientiousness group.

The authors noted that the tendency to experience negative emotions, as is the case in high Neuroticism and low Conscientiousness, contributes to chronic inflammation over time, and inflammation increases bacterial translocation from the gut to the bloodstream and to other organs, potentially leading to infectious episodes. Additionally, high Conscientiousness individuals exhibited a significantly increased abundance of Lachnospiraceae, bacteria that produce butyrate, an agent with anti-inflammatory action.

With this study, the authors suggest that different personality traits might be linked to different bacterial profiles in the gut.

To read the full study, click the link.

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