Researchers at the University of Porto report preliminary associations between gut and oral microbiota composition and self-reported psychopathic traits in 200 adults. Higher abundances of Allisonella, Prevotella and C. evryensis correlated with stronger psychopathy scores, while T. vincentii correlated negatively. The study is exploratory and correlational, relying on self-reports and a modest sample, so causality cannot be inferred. The authors call for larger, longitudinal research to test mechanisms and directionality.
Gut Microbes May Be Linked To Psychopathic Traits, Small Study Suggests
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A preliminary, as-yet-unpeer-reviewed study from researchers led by Carolina Costa at the University of Porto reports an association between the composition of gut and oral microbiota and self-reported psychopathic traits in a sample of 200 adults. The authors caution the findings are correlational and exploratory, but the results invite further study of the gut–brain axis in extreme personality traits.
Study Design
The team collected questionnaire responses and biological samples (blood, saliva and feces) from 200 adult volunteers. Participants completed a validated survey designed to measure subclinical psychopathic traits. The researchers then characterized bacterial composition in oral and gut samples and tested for links between microbial taxa and questionnaire scores.
Key Findings
Overall microbial diversity in the gut and mouth did not show a straightforward relationship with psychopathy scores. However, higher questionnaire scores were associated with greater abundances of three specific bacteria and a lower abundance of one:
- Allisonella, Prevotella, and C. evryensis were positively associated with stronger psychopathy scores.
- T. vincentii showed a negative association with psychopathy scores.
The authors highlight Allisonella because prior work has linked the genus to inflammatory processes and some human disease states; inflammation is a mechanism implicated in other psychiatric conditions. They also note previous evidence that Prevotella is associated with differences in brain regions involved in emotion, attention and sensory processing.
Limitations And Interpretation
The authors and independent observers emphasize several important caveats: the study is modest in size (200 participants), relied on self-reported questionnaire data that may be biased, and used an unedited version of the manuscript made available by the journal Translational Psychiatry. Findings are correlational — the study cannot establish that microbial differences cause psychopathic traits. The relationship may be bidirectional or reversed: dietary patterns, hormonal differences or other behaviors linked to psychopathy could themselves shape the microbiome.
"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."
Why It Matters
The study opens a provocative line of inquiry into how microbes and human behavior might interact. While the results are far from conclusive, they point to specific microbial taxa that merit follow-up in larger, more diverse and longitudinal studies that can test causality and mechanisms.
Bottom line: Interesting preliminary associations were observed between certain gut/oral bacteria and psychopathy questionnaire scores, but the findings are exploratory, limited by sample size and design, and do not demonstrate causation.
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