The Secret Lies in The Gut: Probiotics May Help Relieve Depression in The Elderly

Could taking care of your gut help treat depression? A study with elderly people found that probiotics added to traditional treatment provided an extra improvement in symptoms of depression and anxiety, reinforcing the surprising connection between the gut and the brain.

In recent years, scientists have been investigating a surprising connection between the gut and the brain. This relationship, known as the gut-brain axis, suggests that the bacteria that live in our digestive system can influence mood, anxiety, memory, and even the risk of developing mental disorders.

Based on this idea, researchers have been studying whether probiotics, microorganisms considered beneficial for gut health, could complement traditional treatments for depression.

To investigate this possibility, researchers conducted a study with elderly people aged 60 or older who had moderate depression. All participants were already receiving conventional antidepressant treatment prescribed by their doctors. The aim was to discover whether adding a probiotic containing two specific species of bacteria, Lactobacillus helveticus and Bifidobacterium longum, could provide extra benefits compared to a placebo, which was identical in appearance but did not contain live bacteria.

The study was carefully designed to reduce bias. Participants were randomly assigned to two groups. Half received the probiotics daily for 12 weeks, while the other half received a placebo.

Neither the patients nor the researchers knew who was receiving which treatment during this phase, a strategy known as a double-blind study. After the initial three months of supplementation, all participants continued to be monitored for another three months, totaling 24 weeks of observation.

Throughout the study, researchers assessed various aspects of the participants' mental and physical health. In addition to depressive symptoms, they also analyzed anxiety levels, quality of life, cognitive performance, biological markers linked to brain health, and the composition of gut bacteria.

One of the biomarkers evaluated was brain-derived neurotrophic factor (BDNF), a protein important for the survival and communication between neurons, frequently associated with brain plasticity and recovery from depression.

The results showed that both groups improved significantly over time. Symptoms of depression and anxiety decreased during follow-up, which was expected since everyone continued to receive conventional antidepressant treatment.

However, participants who received probiotics had, on average, slightly lower levels of depression and anxiety when compared to the placebo group. Although this difference was considered modest, it suggests that probiotics may offer an additional benefit for some people.

Another interesting finding was that participants who received probiotics had higher levels of brain-derived neurotrophic factor. In theory, this could indicate a more favorable biological environment for brain health and neuron adaptation. Furthermore, stool analysis confirmed that the administered bacteria managed to temporarily colonize the participants' intestines, demonstrating that the supplementation actually altered the intestinal microbiota.

On the other hand, the researchers found no additional benefits of probiotics in quality of life. Both the placebo group and the probiotic group showed significant improvements in this aspect, but without significant differences between them. It is also important to note that more than half of the participants dropped out of the study over the six months, which limits the strength of the conclusions and indicates the need for larger and more robust research.

The authors conclude that probiotics may offer modest help in controlling symptoms of depression and anxiety in older adults when used alongside conventional treatment. Although the results are promising, they do not suggest that probiotics replace antidepressants or medical follow-up.

Instead, they reinforce the growing evidence that gut health can play an important role in mental health, paving the way for new complementary approaches in the treatment of depression.

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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 (PRODG)

Preeti Sinha, Prasun Chatterjee, Preethy Kathiresan, Karishma Sundara Raju, Rasika Panwar, Aparna Mukherjee, Gunjan Kumar, Jerin Jose Cherian, Anoop Velayuthan, Avinash Chakrawarty, Sarnendu Mondal, Manoj Kalita, Spriha Kamboj, Sreyashi Sen, Mounamukhar Bhattacharjee, Manaswini Mondal, Kalyan Bhowmik, Sovonlal Mukherjee, Indranil Saha, Atanu Kumar Dutta, Asim Saha, Amit Chakrabarti, Abhinaba Ghosh, and Saibal Das

Journal of the American Geriatrics Society. 17 June 2026

DOI: 10.1111/jgs.70530

Abstract: 

To evaluate the efficacy of adjunct probiotic supplementation (Lactobacillus helveticus and Bifidobacterium longum) alongside standard care compared to placebo in older adults with moderate unipolar depression. A randomized, double-blind, placebo-controlled pilot trial was conducted at two tertiary centers. Fifty-eight participants (≥ 60 years) with moderate depression were randomized 1:1 to receive daily probiotics or a placebo for 12 weeks, alongside standard antidepressant care. They were followed up for another 12 weeks. The primary outcome was depression response (≥ 50% Montgomery-Åsberg Depression Rating Scale [MADRS] score reduction). Secondary outcomes included anxiety (General Anxiety Disorder 7-Item [GAD-7]), cognition, quality of life (WHOQOL-BREF), serum brain-derived neurotropic factor (BDNF), and gut microbiota profile. Mixed-effects models showed significant improvement over time in depressive symptoms (MADRS: F = 32.0, p < 0.001) and anxiety (GAD-7: F = 13.1, p < 0.001). Overall scores were lower in the probiotic group compared with the placebo group for both MADRS (F = 12.7, p = 0.001) and GAD-7 (F = 10.7, p = 0.002), although group × time interactions were not significant. Quality-of-life domains improved markedly (all F > 100, p < 0.001) without additional benefit from probiotics. Escitalopram-equivalent antidepressant dose and benzodiazepine use influenced selected outcomes. The probiotic group also had a significantly higher serum BDNF level and increased fecal abundance of supplemented strains vs. the placebo group. The attrition rate was > 50% over 24 weeks. In this pilot PRODG trial, adjunct probiotics produced modest overall advantages for depressive and anxiety symptoms compared with placebo but did not enhance quality-of-life beyond usual improvement − both groups improved substantially, and trajectories over 24 weeks were largely parallel across follow-up.