In the context of a recent study, Portuguese researchers have highlighted a statistical association between the composition of our microbiota and personality traits related to psychopathy. For researchers, considering the microbiota–gut–brain axis in neurobiological research on psychopathy could, in particular, help identify new biological markers for mental health.
A Statistical Link with Psychopathic Traits
First, it is worth recalling that psychopathy is a complex personality disorder. It is typically characterized by emotional detachment, a lack of empathy, and antisocial behaviors. However, unlike common beliefs, it is not a mental illness. Moreover, not all psychopaths are criminals, as many are fully integrated into society.
The Institute of Health Research and Innovation in Health (i3S) at the University of Porto (Portugal) published a study on this disorder in the journal Translational Psychiatry on August 7, 2026. Specifically, this work explored for the first time the links between the composition of our microbiota and subclinical psychopathic personality traits, meaning traits that are not diagnosed in legal psychiatry.
As many as 200 volunteers participated in the study, whose personality traits were assessed using psychological questionnaires. After analyzing the saliva samples of these individuals, the scientists concluded that, despite only a small variation in overall microbial diversity, the presence of certain specific bacteria has a statistical link with psychopathic traits such as a lack of empathy, impulsivity, manipulation, and other antisocial behaviors.
Negative but Also Positive Associations
Statistically, a higher presence of bacteria belonging to the genera Allisonella and Prevotella is associated with higher scores of psychopathic traits. The same observation holds for the species Cloacibacillus evryensis. By contrast, the microbe Treponema vincentii showed a negative association. In other words, the more of this microbe is present, the lower the scores of psychopathic traits tend to be. Additionally, the researchers noted fluctuations in glucose and taurine in the stools of profiles exhibiting these behavioral traits. Taurine, a natural amino acid derivative found in the human body, plays roles such as anti-stress effects and acts as a protector and regulator of the nervous system.
“The results show that certain intestinal and oral bacteria are associated with psychopathic traits within the population, which suggests that the microorganisms present in the body could be linked to processes involved in emotions and social behavior.”
What Perspectives Do These Results Open?
For the Portuguese scientists, caution is warranted. Indeed, the study does not prove that bacteria cause psychopathy. Given that the communication between the microbiota and the brain is bidirectional, it is quite possible that personality traits shape the microbiota rather than the reverse. Additional work will therefore be necessary to better understand the mechanism at play.
Typically, neurobiological research on psychopathy focuses on structural brain abnormalities, particularly in the prefrontal cortex. Yet, the study from Portugal highlights the microbiota–gut–brain axis. These preliminary findings could pave the way for identifying new biological markers for mental health or the development of targeted interventions through nutrition or probiotics.
