The gut–brain axis and the impact of probiotics on symptoms of depression: a review of the evidence

Depressive and digestive disorders are both highly impactful and prevalent. Psychological and gastrointestinal health have been shown to be linked via the gut–brain axis. This link has led to the use of probiotics with the aim of treating depression- and anxiety-related conditions, including major depressive disorder. The efficacy of various probiotics for treating depression symptoms has been investigated in a number of studies on animal models and human subjects. Positive associations between probiotics and reduced depression have been linked to impacts on the immune system, mucosal health and a reduction in inflammation associated with the pathophysiology of depression. There are indications that probiotics may be a safe and effective therapeutic option in depression. This article explores this background and reviews the available evidence.