Effects of Probiotics on Symptoms of Depression

Preclinical and clinical studies have shown that consuming probiotics can improve mood, anxiety, and cognition, as well as alter brain activity in both rodents and healthy humans. Data from our recent open-label, 8-week pilot study provided the first evidence of these effects in depressed patients, with significant improvements observed in overall mood, anhedonia, and sleep quality. To further support this evidence and expand upon the search for biomarkers in depression, data from this pilot study is being used to plan a 16-week, double-blind randomized placebo-controlled trial to assess the effects of probiotics on depression. Participants diagnosed with depression recruited from the greater Kingston area will orally consume a probiotic supplement containing Lactobacillus helveticus and Bifidobacterium longum (Probio'Stick, Lallemand Health Solutions) or placebo once daily. Participants will undergo clinical assessments measuring mood, anxiety, cognition, and sleep using a battery of validated clinical scales to assess efficacy of the probiotic alleviating depressive symptoms; sleep will also be assessed objectively with an ambulatory polysomnogram. Neuroimaging data will be collected using magnetic resonance imaging and electroencephalography to look at functional, structural, and electrical changes in the brain associated with consumption of the probiotic. Molecular data will be collected from blood, stool, and urine samples to look at levels of cytokines and serotonin, and explore potential genes and proteins that may predict outcomes in depression. An informatics-based approach will be used to integrate clinical, neuroimaging, and molecular data to look for biomarkers that indicate disease state and predict antidepressant-like response to the probiotic. Results: We expect results to replicate and expand on our pilot data, demonstrating that probiotics are effective in alleviating symptoms of depression, and to find biomarkers that will predict these outcomes. The findings from this study will contribute robust scientific data that is currently lacking in this emerging field.