In bound-to-be-controversial new research, scientists claim they’ve discovered a link between the specific balance of microflora in the gut and psychopathic behavior

As detailed in a yet-to-be-peer-reviewed study, a team of researchers led by University of Porto biomedical scientist Carolina Costa say they’ve found the first-ever evidence of how microbiota could influence traits linked to psychopathy — a controversial personality construct characterized by lack of empathy, poor behavior control, as well as antisocial and in extreme cases criminal behavior.

As Science Alert points out, previous research has found that psychopaths can share similar brain structures, including pathways in the prefrontal cortex. The latest paper, however, suggests those links could even extend into the microbiome.

“We hypothesized that the composition of the gut and oral microbiota may be associated with subclinical psychopathic personality traits,” the researchers wrote in the paper, an “unedited version” of which was shared by the journal Translational Psychiatry. “To our knowledge, this is the first study to explore this association.”

Costa and her colleagues examined the answers of 200 adult participants who filled out a questionnaire that was specifically designed to measure psychopathic traits. They also analyzed blood, saliva, and fecal samples from the participants for bacterial composition.

While the diversity of gut and oral microbes showed no clear links to psychopathic traits in itself, those who showed stronger psychopathic traits had a higher abundance of three kinds of bacteria when compared to those with weaker psychopathic traits.

“Allisonella, Prevotella, and C. evryensis showed significant positive associations with psychopathy scores, while T. vincentii was negatively associated,” the researchers concluded. The roles of these microbacteria range from helping in digestion and other metabolic processes, to assisting in warding off infections.

The team suggests that Allisonella, in particular, has been linked to human diseases and has been found to promote inflammation, a “key factor in psychiatric disorders such as anxiety and depression,” thereby suggesting a “possible link to psychopathy.”

Prevotella has also been linked to “differences in brain regions responsible for emotional, attentional and sensory processing, leading to a deficit in specificity of encoding contextual details of incoming stimuli.”

The claims are certain to be controversial. For one, the sample size was on the smaller side and relied on self-reported findings, which could greatly skew results as they’re susceptible to bias. Results could also vary depending on geographic regions, the researchers point out.

“Finally, as findings are correlational, causality cannot be established, especially given the bidirectionality of microbiota-brain communication,” they concluded.

In other words, it may actually be an inverse relationship, with the balance of the gut microbiome being caused by psychopathic traits instead of the other way around.

“For instance, psychopathy-linked factors, such as eating behaviors and hormonal differences could be responsible for shaping gut microbiota composition,” the researchers wrote.

It’s nonetheless a fascinating investigation into the extremes of human behavior — though plenty of future research is needed to investigate more thoroughly.

More on the gut: How Your Gut Controls Your Mind and What to Do About It