When we feel danger or anxiety we can notice how our stomach suffers, even at the same moment in which we are suffering. Similarly, when we fall in love we feel "butterflies in the stomach."
However, beyond rhetoric or having to hurry to go to the bathroom, it seems that going through a bad experience can change the microbiome, the colony of microbes that inhabits our stomach and that helps us digestion (and in part, it influences our mood and other cognitive processes).
These are the conclusions that are drawn from a recent study published in Microbiome.
In this study, the authors analyzed the microbiomes of a group of students with irritable bowel syndrome, a fairly common chronic condition marked by pain in the stomach, gas and indigestion. They did the same in a control group of healthy volunteers, and also collected brain scans, stool samples and biographical information from participants in both categories.
Those in the first group, it seems, were much more likely to show anxiety and depression.
When the researchers divided the subjects affected by irritable bowel syndrome into two smaller groups (those who had a microbiome indistinguishable from that of a healthy control and those with notable differences) found that the subgroup with different microbiomes he also had more history of trauma in early life and his symptoms lasted longer.
What the authors conclude is that it is possible that the signals that the intestine and its microbes get from the brain of an individual with a history of childhood trauma can lead to life-long changes in the intestinal microbiome.
If it is true that the intestine influences the brain just as the brain affects the intestine (that is, that an altered microbiome would also influence the brain in a certain way), these results can have enormous implications for mental and physical health.
Something not so strange if we consider, as the neurobiologist explains Michael Gershon in his book The second brain, that 95% of all serotonin that runs through our body is in the intestine, our second brain.