Exploring the Anxiety Associated with Irritable Bowel Syndrome

By Patrick Yang ‘20

Figure 1. The odd association between anxiety and bowel movements in irritable bowel syndrome is a result of altered gut bacteria.

Figure 1. The odd association between anxiety and bowel movements in irritable bowel syndrome is a result of altered gut bacteria.

While symptoms of abdominal pain, gas, and diarrhea are implied in its name, irritable bowel syndrome (IBS), a common gastrointestinal disorder, is also often accompanied by anxiety. The odd association with gut and brain behavior has led scientists to believe that there is a disorder of unknown cause between gut-brain communication that results in the concurrent symptoms. Recent research on IBS patients has found that the composition of IBS gut microbiota differs in composition than the gut microbiota of healthy individuals. This composition difference may very well be due to infection, antibiotic usage, or dietary changes after the onset of IBS. However, in a research collaboration between McMaster University and the University of Waterloo, researchers led by Dr. Premysl Bercik explored these altered microbiota profiles in an attempt to determine the relation between gut and brain symptoms.

In order to observe whether gut microbiota induced IBS symptoms, the researchers translocated gut microbiota from five healthy control individuals (two male and three female) and eight IBS patients (three male and five female) to 137 mice. Using video imaging, the researchers observed the speed of gastrointestinal transit of ingested food, which they used as a measure of diarrhea. They found it to be higher in the IBS microbiota group due to an increase in water permeability of the infected intestinal walls. In conjunction with experiencing symptoms of diarrhea, the IBS microbiota mice also developed low-grade colon inflammation, which resembles the bowel symptoms of IBS. In terms of brain function, the IBS mice developed anxiety-like behavior, which was demonstrated by their preference for the dark and hesitance to move around. Since the translocation of microbiota resulted in both the gut and brain symptoms of IBS in recipient mice, the study concluded that the altered microbiota composition of IBS patients results in the compromised gut-brain behavior.

This discovery of gut microbiota’s role in altered behavior and intestinal function directs IBS treatment towards microbiota therapies. This study also provides additional evidence towards gut microbiota’s role in other behavioral manifestations, such as Parkinson’s disease.



  1. G. De Palma, et al., Transplantation of fecal microbiota from patients with irritable bowel syndrome alters gut function and behavior in recipient mice. Science Translational Medicine 9, (2017). doi:10.1126/scitranslmed.aaf6397.
  2. Image retrieved from: http://3.bp.blogspot.com/-j24Vb09Q0Oo/UGye-NsEo1I/AAAAAAAAB1k/4dBvJgMHc4M/s1600/IBS.jpg

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