Our bodies react immediately to stress. One effect is the activation of the hypothalamic-pituitary-adrenal (HPA)-axis which then cascades through the intestines causing:
- Altered barrier function
These changes in the gut loop back and then can negatively influence behavior such as damaging memory and inducing anxiety. For a long time, colitis was associated with an anxious personality, causing some to theorize that personality disorders may heighten the condition.
Currently, it is known that this gut-brain axis does indeed cause changes in the gut. Altering the gut microbiota in mice does alleviate stress. One report, in the Proceedings of the National Academy of Sciences outlined how mice consuming broth mixed with a strain of Lactobacillus rhamnosus responded. The rodents showed less anxiety and stress but also produced less of the stress hormone corticosterone than control mice on placebo broth.
How does the immune system interact with this effect?
Researchers demonstrated recently that “ B- and T-cell deficient Rag1-/- mice displayed altered baseline behaviors, including memory and anxiety, accompanied by an overactive HPA-axis, increased intestinal secretory state, dysbiosis, and decreased hippocampal c-fos expression.”
In addition, they found that intestinal changes and behavioral changes were normalized by probiotics, independent of lymphocytes.
The authors concluded in the American Journal of Physiology – Gastrointestinal and Liver Physiology in September of 2014: “ Taken together, these findings indicate a role for adaptive immune cells in maintaining normal intestinal and brain health in mice, and show that probiotics can overcome this immune-mediated deficit in the gut-brain-microbiota axis.”