The more we find out about the microbiome, the more we realize how truly profound its effects are in shaping who we become.
We already know that the microbes in our bodies may affect our emotions – including our fear response – but how far does their influence reach in terms of determining our personality?
The answer, research suggests, is pretty far.
In a new early-release study published in Translational Psychiatry, scientists have found evidence to suggest that microbiota may even influence people's experience of psychopathy, with researchers discovering links between levels of certain gut and oral microbes and psychopathic personality traits.
While the findings have yet to undergo peer review, the researchers say it's the first time we've found evidence of how microbiota could contribute to psychopathic traits, which remain poorly understood in terms of their biological underpinnings.
Psychopathy is a personality construct marked by characteristics including lack of empathy, antisocial tendencies, impulsiveness, and egoism, but where psychopathic personalities emerge from is still not fully clear.
We know that psychopaths can share similarities in brain structure, with certain regions and pathways in the brain, including the prefrontal cortex, often linked with the phenomenon.
But researchers say there has to be more to it.
"Though brain alterations, particularly in the prefrontal cortex and temporo-limbic areas, are suggested to be directly implicated in psychopathy, these alone are insufficient to provide a comprehensive neurobiological explanation for psychopathic behavior," researchers explain in their paper, by first author and biomedical scientist Carolina Costa from the University of Porto in Portugal and her colleagues.
"We hypothesized that the composition of the gut and oral microbiota may be associated with subclinical psychopathic personality traits… To our knowledge, this is the first study to explore this association."
In their research, Costa and her team studied 200 healthy adult participants who filled out the Self-Report Psychopathy Scale-Short Form – a questionnaire designed to measure psychopathic traits – and donated blood, saliva, and fecal samples, which were analyzed for signs of bacterial composition in the body or various metabolic markers.
When people's individual diversity of gut and oral microbes was analyzed, no clear links to psychopathy were found, but the picture changed when the participants' results were compared against one another.
From that perspective, a higher abundance of three specific kinds of bacteria showed a positive association with stronger psychopathic traits.
Carrying more microbes in your gut microbiome from the genera Allisonella or Prevotella – or from the species Cloacibacillus evryensis – could mean you're more likely to show psychopathic traits, based on the analysis here.
It's worth noting that none of these results can speak to causation; the research here only surfaces correlations in the data.
But hypothetically speaking, if these microbes do influence people's behavior towards psychopathic tendencies, then how?
We don't know for sure, but the researchers note that Allisonella has previously been linked to several human diseases, and its potential to promote inflammation, which is associated with anxiety and depression, could help explain its possible role in psychopathy.
Similarly, Prevotella has previously been linked with neuropsychiatric disorders, and is thought to affect emotional processing, while the researchers say C. evryensis's association might be due to its suspected role as a producer of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter involved in systems that regulate impulse control.
Interestingly, one species in the analysis showed a negative association: higher levels of Treponema vincentii in the oral microbiome were linked with lower psychopathy markers, although the researchers admit they don't have an answer for that.
Related: Scientists Developed a Questionnaire to Identify if Your Cat Is a Psychopath
While a lot more research is needed to better understand how these gut microbes may contribute to psychopathic traits, the findings do give us some important new leads to chase down – and could one day support clinicians in identifying people who show these dark impulses.
"Overall, our findings highlight the potential of microbiota and their metabolic outputs as biomarkers for psychopathic traits in the general population," the researchers write.
"The associations we observed, particularly between specific taxa (e.g., Allisonella, Prevotella, C. evryensis, T. vincentii) and traits such as callousness, manipulation, impulsivity, and anti-sociality, suggest a measurable biological footprint for psychopathy that extends beyond traditional neurocognitive models."
The findings are reported in Translational Psychiatry.
This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.