Advertisements for the various health benefits of different probiotics —for digestive problems but also beyond the gut— are everywhere these days. But do probiotics really work? A new study published in the journal Gastroenterology showed that a specific probiotic can help to treat symptoms of depression in patients who suffer from a common gastrointestinal disorder, irritable bowel syndrome (or IBS).

IBS is one of the most common gut disorders in the world, affecting about 10% of the population, and patients with IBS frequently suffer from psychiatric symptoms, such as depression and anxiety. Little is known about what causes IBS and the related psychiatric symptoms, but the bacteria residing in the gut, collectively referred to as the “microbiota”, have been suggested to play a role.

The new study conducted by researchers at McMaster University shows a link between a probiotic and mood improvement in those with IBS, and adds to the evidence suggesting gut bacteria can communicate with the brain to affect mood and behavior.

The new study adds to the evidence that suggests gut bacteria can communicate with the brain to affect mood and behavior

For the study, researchers recruited 44 IBS patients, who also suffered from mild to moderate depression and anxiety. Half received daily doses of the probiotic Bifidobacterium NCC3001 longum (B. longum), while the other half received a placebo (inactive treatment) for six weeks. Each person filled out questionnaires to measure depression and anxiety, as well as gastrointestinal symptoms. At six weeks, 64% of the people who received the probiotic B. longum had improvements in depression scores, compared to 32% of those who received the placebo. Depression scores remained lower in the B. longum group, even four weeks after the participants had stopped taking the probiotic. However, neither anxiety symptoms nor any of the intestinal symptoms changed with the probiotic treatment.

Using a functional magnetic resonance imaging (fMRI) scan to measure brain activation patterns, the researchers found that improved depression in patients taking B. longum was linked to changes in brain activity, particularly in areas that are associated with mood regulation. By showing patients either fearful or happy images, they found that those taking the probiotic had a reduced reaction to the fearful (stressful) stimuli.

Even though the number of people included in the study was small, making it difficult to know if the results would hold up in larger groups, those who received B. longum also reported improvements in overall global wellbeing and quality of life. The authors noted that a larger study is needed to confirm these findings before this probiotic could be used regularly as a medical treatment for depression associated with IBS. Nonetheless, the results of this study do suggest that the probiotic B. longum has an anti-depressant effect.

“This opens new avenues not only for treatment of patients with functional bowel disorders but also for patients with primary psychiatric disorders, such as major depression” said Dr. Premysl Bercik, associate professor at the Farncombe Institute at McMaster University and lead author of the study.



Pinto-Sanchez MI, Hall GB, Ghajar K, et al. Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: a Pilot Study in Patients With Irritable Bowel Syndrome . Gastroenterology. 2017. doi: 10.1053/j.gastro.2017.05.003.