The human microbiome may influence far more than digestion and immune function. In recent years, scientists have increasingly investigated the trillions of microorganisms living in the gut, mouth and other parts of the body and their possible role in mood, anxiety and behavior.
A new study takes this research a step further by examining whether the composition of the microbiome may also be associated with traits linked to psychopathy. The research was published in an early form in Translational Psychiatry.
The researchers identified associations between specific bacteria found in the gut and mouth and higher scores on measures of psychopathic traits.
Looking beyond the brain
Psychopathy is a complex combination of characteristics that can include reduced empathy, impulsivity, manipulative behavior, egocentrism and antisocial tendencies.
Although previous research has identified differences in brain regions including the prefrontal cortex, scientists are increasingly exploring whether other biological factors may also be involved in these traits.
A research team from the University of Porto in Portugal studied 200 healthy adults. Participants completed a questionnaire designed to assess psychopathic characteristics, while the researchers collected blood, saliva and stool samples to analyze their microbial composition.
Three bacterial groups stand out
Overall microbiome diversity did not show a clear association with psychopathic traits. When the researchers looked at individual microbial groups, however, they identified three bacteria that were more abundant in people who scored higher on measures of psychopathic characteristics.
They belonged to the genera Allisonella and Prevotella, as well as the species Cloacibacillus evryensis.
Some of these microorganisms have previously been investigated for their potential involvement in inflammatory processes and neuropsychiatric functions. Prevotella, for example, has been studied in connection with neuropsychiatric disorders and emotional processing.
C. evryensis is also of interest because it may be involved in the production of GABA, a major neurotransmitter that helps regulate neural activity and plays a role in impulse control.
By contrast, higher levels of Treponema vincentii in the oral microbiome were associated with lower scores for psychopathic traits. The reason for this association remains unclear.
The bacteria have not been shown to cause the behavior
The researchers stress that the findings do not demonstrate a cause and effect relationship.
In other words, the study does not show that particular bacteria cause psychopathic behavior. Other biological, environmental or social factors could influence both the microbiome and certain aspects of personality at the same time.
The relatively small sample size is another limitation, and larger studies will be needed to determine whether the findings can be replicated.
A new direction for research
Despite these limitations, the findings add the microbiome to the growing list of biological factors being investigated in an effort to understand complex aspects of human behavior.
Future research into gut and oral microorganisms could potentially identify additional biological markers associated with traits such as reduced empathy, impulsivity and antisocial behavior.
For now, however, scientists are far from being able to predict an individual’s personality or behavior simply by examining their microbiome.