Gut Brain Connection

Do the trillions of microbes living in the human digestive system affect our mental health and affect – for better or worse – brain or mood disorders?

As recently as seven years ago, the idea that gut bacteria played a role in mental health was considered “crazy”, but in the past few years, more and more research has shown possible effects of all kinds.

The gut microbiome is a hugely complex phenomenon, but nowadays, researchers are “drilling down” to look at specific strains of bacteria and how they may affect specific brain disorders.

Even the mechanism for these effects is not well understood, although the pathway from gut to brain via the vagus nerve is now under intensive research.  Scientists are looking at possible causes of Parkinson’s disease, and maybe autism through errors in proteins transmitted to the brain from bacteria, such as Escherichia coli, that may stimulate “misfolding” in these proteins.

The field of gut-brain interaction is considered “really exciting”, and a few human trials have even begun, but researchers warn to beware of hype.  Once a small study shows promising findings, reports tend to blow them out of proportion, and people may believe that a microbiome pill is just around the corner.

Research into probiotics and diet are also beginning to show some results, although, again, much remains to be untangled in this area.  Some specific treatments are now available, but the results of research are still much less than what disorder sufferers may be hoping for.

There are many years of research ahead before actual treatments may become available.  In addition to Parkinson’s disease, research is beginning in motor neuron disease, Alzheimer’s disease and depression.  Researchers must learn to distinguish different effects of different bacteria, and consider the direction of causality: are certain bacteria more or less present in the gut as a result of the disease, or do the bacteria have some role in causing it?

For more information see:

Willyard, C. How gut microbes could drive brain disorders. Nature 590, 22-25 (2021). doi: