The evidence for the gut–brain connection continues to increase. Plenty of rodent models demonstrate the effects of gut microbiota on emotional and social behaviours, such as anxiety and depression. However, human studies are needed.

In a study by Dr Kirsten Tillisch et al., published in the Journal Psychosomatic Medicine: Journal of Behavioral Medicine, the researchers sought to identify brain and behavioural characteristics of healthy women clustered by gut microbiota profiles. The study resulted in the identification of gut microbiota that interacts with brain regions associated with mood and behaviour, supporting the concept of brain-gut-microbiota interactions in healthy humans.

These findings further support the idea of supplementation with probiotics for mood disorders such as anxiety and depression. Probiotic strains Bifidobacterium longum R0175 and Lactobacillus helveticus R0052, have been shown to reduce markers of psychological distress, reduce anxiety scores and urinary free cortisol levels (a stress indicator), in healthy subjects.

It’s great to see more and more research on the microbiome in the area of mood disorders. At this stage, it is hard to identify whether bacteria in the gut influence the development of the brain and its activity when unpleasant emotional content is encountered, or if existing differences in the brain influence the type of bacteria that reside in the gut. I believe it is most likely a two-way street, and they both influence each other. I’m hopeful that there will be more probiotic strains identified in the very near future and larger clinical trials conducted, so health practitioners such as myself can provide better treatments for better clinical outcomes.


(Messaoudi, Lalonde, et al., 2011; Messaoudi, Violle, et al., 2011; Tillisch et al., 2017)Messaoudi, M., Lalonde, R., Violle, N., Javelot, H., Desor, D., Nejdi, A., … Cazaubiel, J.-M. (2011). Assessment of psychotropic-like properties of a probiotic formulation ( Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in rats and human subjects. British Journal of Nutrition, 105(5), 755–764.

Messaoudi, M., Violle, N., Bisson, J.-F., Desor, D., Javelot, H., & Rougeot, C. (2011). Beneficial psychological effects of a probiotic formulation ( Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in healthy human volunteers. Gut Microbes, 2(4), 256–261.

Tillisch, K., Mayer, E., Gupta, A., Gill, Z., Brazeilles, R., Le Nevé, B., … Labus, J. S. (2017). Brain structure and response to emotional stimuli as related to gut microbial profiles in healthy women. Psychosomatic Medicine, 1.