Daily Probiotics Could Ease Depression and Anxiety in Older Adults, Study Suggests

Standard antidepressants reach a response rate of approximately 50% in older adults, leaving a significant share of patients with moderate depression still struggling. Researchers at the Indian Council of Medical Research's National Institute for Research in Bacterial Infections in Kolkata have now published early evidence that a specific probiotic combination, taken daily alongside existing medication, can modestly but meaningfully improve both depression and anxiety symptoms in people aged 60 and older.

Lactobacillus helveticus and Bifidobacterium longum added to antidepressant care

The PRODG trial, published June 17, 2026, in the Journal of the American Geriatrics Society, enrolled 58 adults aged 60 and older who had moderate unipolar depression and were already receiving standard antidepressant treatment. Participants were randomly assigned to one of two groups: one received a daily supplement containing roughly 6 billion CFU (colony-forming units) of Lactobacillus helveticus and Bifidobacterium longum, and the other received a placebo. The trial ran for 12 weeks, followed by an additional 12-week monitoring phase. Both groups continued their usual antidepressant medication throughout.

These two strains were chosen because prior research suggested they have mood-related benefits, and the study design, randomized, double-blind, and placebo-controlled, was intended to minimize bias in a notoriously difficult-to-study domain.

Modest but meaningful improvement in elderly depression symptoms

By the end of the intervention period, participants in the probiotic group showed greater improvement in validated psychological scores for both depression and anxiety than those in the placebo group. The gains were described as modest but considered meaningful by the researchers. Elevated levels of brain-derived neurotrophic factor (BDNF), a protein essential for brain cell growth and maintenance, were also measured in the probiotic group. Lower BDNF levels have been linked to depression, so the rise suggests the gut-brain axis may be one mechanism through which the probiotics exerted their effect.

Both groups improved substantially over the trial period, which is common in well-managed depression studies and makes it harder to isolate the specific contribution of the supplement. On quality of life measures, the probiotic group did not show a clear additional gain over placebo. Dr. Abhinaba Ghosh, one of the study's authors, was direct about this: "We did not see a change in the quality of life of the patients, probably because this is a pilot study and there weren't enough patients."

The same caveat applies to the positive findings. The gains in depression and anxiety scores are encouraging, but the small sample size limits how firmly anyone can interpret them.

The gut-brain axis as a target for elderly mental health

The rationale for targeting the gut microbiome in older adults with depression draws on a growing body of evidence that the digestive system and the brain communicate bidirectionally through nerves, hormones, and immune molecules. Gut bacteria can influence mood and behavior through this pathway. Research into the neuroactive potential of the elderly gut microbiome has found that while the microbiota-gut-brain axis clearly plays a role in mental health, its specific contribution to depression and cognitive decline in older populations is still not fully understood.

This uncertainty is part of why the PRODG trial focused on two strains with a prior evidence base rather than a broad-spectrum probiotic. Probiotics in this context are positioned as complementary therapy, added on top of antidepressants rather than replacing them. The National Center for Complementary and Integrative Health notes that probiotics and prebiotics are among the most widely used supplements in the United States, second only to vitamins, which means a large share of the public is already consuming these products with varying degrees of evidence behind specific applications.

Key limitations before this finding can be applied widely

The trial's small size, 58 participants, is the most important caveat. As a comprehensive review of probiotic clinical trials from 2014 to 2023 noted, the field as a whole has struggled with small samples, focus on specific patient subgroups, and a lack of consensus on optimal bacterial strains, dosages, and treatment durations. The PRODG trial does not resolve those gaps; it adds one data point to an accumulating pile.

The study also did not enroll immunocompromised patients, and the researchers caution that people in that category should consult a doctor before starting probiotics. The 12-week active phase, while meaningful, may also be too short to capture longer-term effects on quality of life or microbiome composition.

Fecal microbiota profiling was included as an outcome measure, but the published summary does not detail which specific microbial shifts correlated with the mood improvements, a gap a larger follow-up trial could address.

Larger clinical trial planned to confirm the probiotic mood benefits

Dr. Saibal Das, another of the study's authors, stated that the team is planning a larger-scale clinical trial given the encouraging direction of the results. Dr. Ghosh added that the follow-up will specifically aim to resolve the quality-of-life question that the pilot was underpowered to answer.

For now, the finding is best understood as a signal, not a prescription. Two strains of probiotic bacteria, delivered alongside standard antidepressant care for 12 weeks, produced modest improvements in depression and anxiety in a small group of Indian adults aged 60 and older. BDNF levels rose. Quality of life did not budge. The effect is real enough to pursue further, but not yet solid enough to change clinical practice. If the planned full-scale trial replicates the mood improvements in a larger cohort, the case for probiotics as a genuine adjunct therapy in geriatric depression will be considerably stronger.

Evidence rating

EMERGING — 78/100

Caveats:

• This was a small pilot RCT (n=58). Researchers explicitly call for larger trials before drawing firm conclusions.
• Improvement in quality of life was not observed, and the authors attribute this to the limited sample size.
• Both the probiotic and placebo groups showed substantial overall improvement, making the additional benefit of probiotics modest in scale.
• Funding source was not disclosed in the available materials.
• Immunocompromised individuals should consult a healthcare provider before taking probiotics.

Randomized, double-blind, placebo-controlled pilot trial (n=58 adults aged 60+). Demonstrates association between adjunctive probiotic use and modest improvement in depression and anxiety scores alongside elevated BDNF levels, but the small sample limits statistical power and no quality-of-life benefit was detected. Not yet replicated at scale; researchers have announced a follow-up full-scale trial.

References

1. (2026). For the Elderly, Daily Probiotic Consumption Can Relieve Depression and Anxiety. https://www.kompas.id/artikel/en-bagi-para-lansia-konsumsi-probiotik-setiap-hari-dapat-redakan-depresi-dan-kecemasan
2. Stephanie K. Nothelle, Hannah Kleijwegt, Evan Bollens‐Lund, Kenneth Covinsky, Claire K. Ankuda (2024). The effect of dementia on patterns of healthcare use in older adults with diabetes. Journal of the American Geriatrics Society. https://doi.org/10.1111/jgs.19010
3. Paulina Calderón-Romero, Benjamin Valderrama, Thomaz Bastiaanssen, et al. (2024). The Neuroactive Potential of the Elderly Human Gut Microbiome is Associated with Mental Health Status. https://doi.org/10.1101/2024.08.08.607034
4. Ermis Merkouris, Theodora Mavroudi, Daniil Miliotas, et al. (2024). Probiotics’ Effects in the Treatment of Anxiety and Depression: A Comprehensive Review of 2014–2023 Clinical Trials. Microorganisms. https://doi.org/10.3390/microorganisms12020411