This is the Medscape Neurology Minute. I’m Dr Alan Jacobs.

Researchers from McMaster University in Canada have published a randomized, double-blind, placebo-controlled study investigating the effects of probiotics on anxiety and depression in patients with irritable bowel syndrome (IBS).^[1] Forty-four adults with IBS or a mixed-stool pattern, and mild-to-moderate anxiety and/or depression, were randomly assigned to taking daily probiotic Bifidobacterium longum NCC3001 or placebo for 6 weeks.

At week 6, twice as many patients who received the probiotic had reductions in depression scores, while there was no effect on anxiety or IBS symptoms. Patients in the probiotic group also had mean increases in quality-of-life scores and decreases in fMRI-measured responses to negative emotional stimuli in multiple brain regions, including the amygdala and frontolimbic regions, compared with placebo. At 10 weeks, depression scores were reduced in patients given probiotic versus placebo.