Talking About Poop for Mental Illness with a Straight Face

Steven P. Levine, MD, says the implications of altering the microbiome may extend beyond C. difficile to mental health, given the new insight into the connection between the gut and mind.

A “new” antidepressant will hit the market later this year. Without naming names or giving the medication more attention than it deserves, I’ll say it’s merely another “me too” drug to throw onto the pile. We might even be expected to bleat like sheep when we’re prescribing it, but I’ll have to check the prescriber’s information to confirm that. Pardon the obnoxious sarcasm, but I’m not impressed.

Then again, perhaps there’s some value in being served reheated leftovers. They provide a contrast to the truly revolutionary ideas that provoke us to attention. For example, a subject that currently has me so excited that I can hardly sleep is the microbiome. Over the past few years, the Human Microbiome Project of the National Institutes of Health (NIH) has sought to “characterize microbial communities found at multiple human body sites and to look for correlations between changes in the microbiome and human health.”

This definitely passes the “it just makes sense” test. We are way outnumbered by the number of cells and amount of DNA in the microbes that live on and in us, so our recognizably human form is actually more “critter” than human. If you lost a finger, then you would expect that hand to function differently. In the same way, if your intestinal flora colonization is altered, then it makes sense that it may result in a functional change. Therefore, gut flora may be just as important to our overall physiology as a finger is to a hand.

A more dramatic and well-established example of this involves Clostridium difficile colitis, a debilitating illness caused by the proliferation of diarrhea-inducing bacteria after antibiotic treatment has wiped out healthy gut flora. A recent advancement in the treatment of this disease involves restoring the healthy balance of intestinal microbial flora through fecal transplant from a healthy donor, which has been deemed a rapid and highly effective treatment.

However, the implications of altering the microbiome extend beyond C. difficile to inflammatory bowel diseases like Crohn’s disease and ulcerative colitis, obesity, cancer, skin diseases, and even mental health. We’ve long known that information travels from the mind to the gastrointestinal system — resulting in thoughts such as “I was so nervous that I had butterflies in my stomach” and “I am so upset, I’m sick to my stomach” — but it’s also likely that information travels in the other direction, as well. Thus far, early investigation into this two-way connection has focused on anxiety disorders, including obsessive compulsive disorder (OCD).

Maybe I’m just tickled by the endless possibilities for scatological humor, but I believe the converging lines of evidence point to the potentially important roles of inflammation, immune response, and epigenetics in the pathogenesis of mental illness — all of which may be influenced in some way by the state of our microbiome. Even so, this is a highly complex subject that’s still in its infancy, and we don’t know where it will lead yet. We also don’t know the most effective time to intervene or even how to do the procedure, so don’t try this at home, folks. But if further research bears out the promise it holds, I will apologize to my patients for the yuck factor and happily recommend interventions like fecal transplantation over the next “me too” pile.