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.