Although researchers found promising results of probiotics’ effects on mental well-being through the gut, they call for rigorous, longitudinal research to “clarify the beneficial effects of probiotics on the gut-brain axis and mental health.” In their review of randomized controlled trials using functional MRI methodologies, they observe methodological variability and limited sample sizes. Task-based functional MRI studies on healthy individuals indicate that probiotics modulate brain activity related to emotional regulation and cognitive processing. Studies also suggest that probiotics could normalize brain function in patients with major depressive disorder and irritable bowel syndrome (IBS).
