IBD, the Microbiome, Mental Health: Inflammation is the Key

The link between inflammatory bowel diseases (IBD) and mental health issues has long been observed, and I have covered the topic before on this blog.  (Look here and here, for example.) On the one hand, it makes sense:  living with persistent pain, diarrhea, fatigue, etc. would affect anyone’s emotional well-being.  But that is not the whole story. About 40% of those with IBD experience anxiety and depression: this is not a rare issue.  As my old mentor, a well-known physician, always said, “Inflammation is inflammation,” meaning, of course, that inflammation is body-wide, and everything in the body affects everything else.

According to an article on Medical News Today, at least 30% of people with IBD experience depression, anxiety or both.[i]  Says Dr. Honig, the director of research innovation at the Crohn’s and Colitis Foundation.  And not surprisingly, those who experience anxiety and depression tend to have worse outcomes.  It makes sense when you consider that likely, these people have the most inflammation – and too, our emotions of course, also cause systemic bodily changes.

A new study in the journal, Science, has found that (in an animal model, thus far) inflammation actually closes down the gut-brain axis by adversely affecting the communication signals between the two via the cerebrospinal fluid.  This back-door passageway – between the blood and the CSF – allows smaller molecules to make their way through the brain, unimpeded by the blood-brain barrier which prevents large molecules passing into the brain through the blood stream.   At the base of the brain is a membrane called the choroid plexus, which serves as a barrier between the CFS and the bloodstream.  When someone is healthy this membrane connects the brain with the rest of the body for nutrient and gut metabolite exchange.  However, during cases of extreme inflammation, the barrier closes down. The study’s authors believe that shutting this pathway down is a protective mechanism:  the body’s attempt to protect the brain from damage.  When the choroid plexus shuts down, anxiety increases, as does memory defects.

Thus, any treatment that reduces inflammation should help to restore normal communication between the gut and the brain, via the choroid plexus.

Interestingly, these same scientists previously found a barrier that prevents gut bacteria from passing into another vital organ, the liver, via the bloodstream.  During periods of inflammation in the intestines, this barrier is disrupted which allows gut bacteria to make their way into the liver, further promoting systemic inflammation.  People with ulcerative colitis, it has been found, have disrupted gut-vascular barriers.

A second paper, published in Pharmacological Reviews, found that even low-grade inflammation, via poor diet and poor life choices, affects brain chemicals and circuits that lead to a loss of motivation and an unwillingness to engage in formerly pleasurable activities – symptoms so often seen in those with depression.[ii]  In this case, the belief is that this is an adaption on the part of the brain to conserve energy – which of course, leads to a vicious cycle.  A lack of motivation leads people to continue to engage in the very behaviors (being too sedentary, making bad food choices, etc.) that lead them to have a lack of motivation in the first place.

To sum it up – yup, excessive inflammation is really bad.

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[i] https://www.medicalnewstoday.com/articles/ibd-may-disrupt-mental-health-by-breaking-gut-brain-link

[ii] https://medicalxpress.com/news/2021-10-outline-inflammation-depression.html