Probiotics Decrease Depression in Irritable Bowel Syndrome Patients, Not Anxiety

Probiotics can reduce depression, but not anxiety in patients with irritable bowel syndrome (IBS), a recent study found.

Although it is known that probiotics can reduce symptoms of IBS, little is known about its impact on psychiatric comorbidities.

In a study published in Gastroenterology, investigators sought to evaluate the effects of Bifidobacterium longum NCC3001 (BL) on depression and anxiety in patients with IBS.

Included in the randomized, double-blind, placebo-controlled study were 44 adults with IBS and diarrhea or a mixed-stool pattern, plus mild to moderate anxiety and/or depression.

The study was conducted at McMaster University in Canada from March 2011 to May 2014. During the patients’ screening visit, blood samples were collected and clinical history and symptoms were assessed.

The participants were randomized to receive either daily BL or placebo for 6 weeks. At week 0, 6, and 10, the investigators used validated questionnaires to determine the patients’ levels of anxiety, depression, quality of life, somatization, and IBS symptoms.

At week 0 and 6, stool, urine, and blood samples were collected, and functional MRI (fMRI) tests were performed. The investigators also assessed brain activation patterns, fecal microbiota, serum markers of inflammation, urine metabolome profiles, and neurotransmitters and neurotrophin levels.

The results of the study showed that at week 6, 14 patients in the BL arm experienced a reduction in depression scores of 2 points or more on the Hospital Anxiety and Depression scale, compared with 7 patients in the placebo arm. BL had no significant effect on anxiety or IBS symptoms.

With the fMRI analysis, the investigators found that BL reduced responses to negative emotional stimuli in several areas of the brain, including amygdala and fronto-limbic regions, compared with placebo.

Although fecal microbiota profiles, serum markers of inflammation, and levels of neurotrophins and neurotransmitters were similar between the groups, patients in the BL arm experienced a reduction in urine levels of methylamines and aromatic amino acids metabolites.

Depression scores were reduced at week 10 in patients administered BL compared with placebo, according to the study.

“Probiotic BL reduces depression but not anxiety scores and increases quality of life in patients with IBS,” the authors concluded. “These improvements were associated with changes in brain activation patters that indicate that this probiotic reduces limbic reactivity.”