Probiotics may modestly boost depression treatment in older adults

A small trial in India suggests probiotics may give older adults being treated for depression a modest extra lift, but the findings stop well short of proving a new therapy. In 58 participants age 60 and older with moderate depression, the probiotic group improved a little more than the placebo group while both sets of patients continued standard antidepressant care.

The study, published online June 17, 2026 in the Journal of the American Geriatrics Society, was a randomized, double-blind, placebo-controlled pilot trial run at two tertiary centers. Participants were assigned 1:1 to a daily probiotic or placebo for 12 weeks, then followed for another 12 weeks. The formulation combined Lactobacillus helveticus and Bifidobacterium longum.

Researchers defined the main outcome as depression response, meaning at least a 50% drop in Montgomery-Åsberg Depression Rating Scale scores. They also tracked anxiety, cognition, quality of life, serum brain-derived neurotrophic factor, or BDNF, and fecal microbiota profiles. Mixed-effects models showed significant improvement over time in depressive symptoms and anxiety, and the probiotic arm did slightly better than placebo on those measures.

The results fit a growing scientific interest in the gut-brain connection, the theory that intestinal microbes may help shape mood and behavior through biological pathways still being mapped. BDNF, a marker often studied in mental-health research because it is tied to nerve-cell growth and survival, and the stool microbiota analysis added biological context, but neither turns the study into proof that probiotics treat depression.

That distinction matters. The researchers said the gains were novel, but they were also modest, and the Wiley newsroom summary said the probiotics improved symptoms without producing clear additional gains in quality of life versus placebo. The trial suggests probiotics could one day be considered as an adjunct to standard depression care, especially for older adults already on antidepressants, not as a replacement for established treatment.

The investigators are now planning a larger follow-up trial, a necessary next step before doctors can judge who might benefit most and whether the effect holds up in more diverse groups. The paper lists Saibal Das and Abhinaba Ghosh as co-corresponding authors and includes researchers affiliated with NIMHANS Bengaluru, AIIMS New Delhi, the Indian Council of Medical Research in New Delhi, the ICMR National Institute for Research in Bacterial Infections in Kolkata, AIIMS Kalyani and Tata Medical Centre in Kolkata. For now, the evidence points to promise, not proof.