We all know that a hungry stomach can lead to the dreaded feeling of hanger, but it seems that our gut may have much more of an impact on our emotions than we previously realised.
A new study looked at how ‘microbiota’ bacteria in the human gut influences our emotional responses, as the evidence suggests there is a direct correlation between the two.
This study was the first time behavioural differences had been examined in healthy humans rather than animals. In the past, research on the relationship between the brain in our heads and the ‘second brain’ in our stomachs had only been conducted on rodents.
Gastroenterologist Kirsten Tillisch, and her team at the University of California, took faecal samples from 40 healthy females, aged between 18 and 55-years-old, for laboratory analysis.
Microscopic examination revealed that the samples fell into two distinct groups of bacterial composition - one had a greater abundance of a bacterium genus ‘Bacteroides’ and the other had more ‘Prevotella’ bacteria.
After establishing the composition of both groups, the participants were sent for MRI scans to look more closely at their emotional responses. They were shown images designed to provoke emotions; positive, negative and neutral.
They found that the group with greater abundance of ‘Bacteroides’ had thicker grey matter in their frontal cortex - the region which processes complex information - also a larger hippocampus (memory centre) volume.
Whereas those with more ‘Prevotella’ bacteria had lower volume in those same areas, and demonstrated greater connections between emotional, attentional and sensory regions.
This lead to them reporting greater levels of anxiety, distress and irritability when looking at negative images, compared to the ‘Bacteroides’ group.
The researchers speculated that this discrepancy could be because the hippocampus helps us to regulate our emotions, and so with less hippocampal volume, the negative imagery packs a greater emotional punch.
The authors said: “Reduced hippocampal engagement to negative imagery may be associated with increased emotional arousal.”
And while the subjects in the study were all deemed healthy, the team say that these patterns could be representing “vulnerability factors” for forms of illness, both mental and physical.