Daily probiotic may ease depression symptoms in older adults, study finds

A daily probiotic may offer extra relief for older adults living with moderate depression, but a new pilot trial stops well short of proving it as a treatment. In 58 participants in India aged 60 and older, adding Lactobacillus helveticus and Bifidobacterium longum to standard care was linked to modest improvements in depressive symptoms and anxiety over 12 weeks.

The study, titled Efficacy of Adjunct PRObiotics as Compared to the Standard Care in Moderate Unipolar Depression Among Geriatric Patients: A Randomized Double-Blind Placebo-Controlled Pilot Multi-Center Trial, was published online June 17, 2026 in the Journal of the American Geriatrics Society. Participants were assigned 1:1 to probiotic or placebo while continuing standard treatment, then were followed for another 12 weeks, a design meant to test whether the supplement added anything beyond routine care.

Researchers measured the main outcome as depression response, defined as at least a 50% reduction on the Montgomery-Åsberg Depression Rating Scale. They also tracked anxiety with GAD-7, cognition, quality of life, serum brain-derived neurotrophic factor and gut microbiota profiles. That mix of psychological and biological measures matters because it goes beyond symptom scoring alone and tries to link mood changes to the gut-brain axis.

The abstract reported significant improvement over time in depressive symptoms and anxiety, but no clear additional gain in quality of life compared with placebo. Both groups improved substantially during follow-up, suggesting standard treatment did much of the work, even as the probiotic group showed added benefit. The finding points to an adjunct, not a substitute, for antidepressant care.

That caution is central. The trial was small, the participant pool was limited to older adults in India, and the study was designed as a pilot, not a definitive test. Co-corresponding author Saibal Das, of the Indian Council of Medical Research - National Institute for Research in Bacterial Infections in Kolkata, said the results were novel and that the team is planning a larger follow-up trial. Co-corresponding author Abhinaba Ghosh, a physician-neuroscientist at Tata Medical Centre in Kolkata, said he wants to develop affordable healthcare solutions with broader public health impact.

The broader public-health case is real. The World Health Organization says depression affects about 5.9% of adults aged 70 and older, and social isolation and loneliness affect about a quarter of older people. The Centers for Disease Control and Prevention says depression is not a normal part of aging and is treatable. For now, the new trial adds to growing but still preliminary evidence that the gut-brain connection may one day support low-cost, practical add-on care for depression, especially if larger studies identify which patients benefit most.