Early clinical evidence shows probiotics ease geriatric depression symptoms

A pilot clinical trial has found that administering probiotics to older adults with moderate depression, receiving standard care, had modest yet meaningful reductions in depression and anxiety symptoms compared to a placebo.

Nutrition Insight speaks with the senior authors to learn more about the study involving 58 participants, 60 years or older. They were administered either Lactobacillus helveticus and Bifidobacterium longum (~6 billion CFU daily) or a placebo for 12 weeks. The paper notes that these strains were chosen based on previous evidence of benefits on mood and anxiety. 

“We found that adding specific strains of probiotics has the potential to enhance improvement in depression and anxiety,” affirms Dr. Abhinaba Ghosh, Ph.D., physician, neuroscientist, and medical research consultant at Tata Medical Center, India.

“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. We plan to address this in a follow-up full-scale clinical trial.”

Probiotics’ mechanistic insights

The randomized, double-blind, placebo-controlled study in the Journal of the American Geriatrics Society, points out that standard antidepressant treatments are often limited in effectiveness for older adults with depression, with ~50% response rates and a high placebo response and chance of negative effects.

Standard antidepressants show only ~50% response rates in older adults with depression.Based on this, the researchers call for new adjunct therapies to improve results for geriatric depression. The team measured psychological scores, brain-derived neurotrophic factor (BDNF) levels, and gut bacteria of the participants.

“Increased blood BDNF gives us the mechanistic insight into how these probiotic strains may help improve brain function. Beneficial microenvironmental changes that are happening inside the gut can extend to the brain by leveraging the gut-brain axis,” explains Dr. Saibal Das, Ph.D., a scientist at the Indian Council of Medical Research — National Institute for Research in Bacterial Infections.

“Blood BDNF level is the indirect evidence of that pathway being activated by means of using these specific strains of probiotics.”

Ghosh adds that the gut bacteria testing involved analyzing the microbiome before and after treatment in the placebo and probiotics groups. This enabled researchers to learn that the changes they recorded were caused by the introduction of bacteria and not by a placebo effect or other random factors.

“Only the probiotics group showed a proven increased presence of our bacteria of interest post-treatment, thereby confirming adherence to the probiotics administration schedule,” he underscores.

Improving quality of life 

Based on the measurements of gut bacteria before and after treatment and BDNF levels, researchers found that probiotics helped improve patients’ symptoms but did not clearly see quality-of-life improvement. However, Das says this is counterintuitive.

Participants received around 6 billion CFU of probiotics daily for 12 weeks.“Something that improves anxiety and depression should also improve the quality of life of the patients. We both think that this is because of the smaller number of patients, as this is a pilot study.”

“In all likelihood, a full-scale clinical trial will show improvement in the quality of life as well, but that must be tested before we can claim that with certainty,” he stresses. 

Need for larger clinical tests

According to Ghosh, another prospect could be that long-term therapy could potentially improve quality of life. “Again, like everything else in science, that must be tested first before we can comment with certainty.”

“Science is a step-by-step process. We have to lift ourselves up to the next level by leveraging the current level.”

Das adds that the pilot study can be used as a basis to develop a large-scale clinical trial to bring more certain results and “reach the point of statistical decisiveness,” which he underscores is the bare minimum requirement for scaling his team’s research.

“Further, it should be scaled up to the public health level and administered to a larger population. It all depends on how many research grants we can secure to recruit enough people for the clinical trial.”

Meanwhile, for older patients considering taking probiotics to improve mental health, Ghosh says they should be aware that choosing one strain or more might not bring the expected results.

“Our study is limited to these two strains only. Also, note that for immunocompromised patients (HIV, cancer), any external bacterial strains can pose threats because of the poor immunity. It is best to touch base with the health care provider beforehand.”

Nutrition approaches to depression

A recent review of over-the-counter herbal medicinal products and dietary supplements identified 64 products evaluated for depression. Products with promising but limited evidence include folic acid, lavender, zinc, tryptophan, rhodiola, and lemon balm. The authors urge that future research focus on these products and that trial safety reporting must be improved. 

Meanwhile, a clinical trial found that a dose of psilocybin brings sustained reductions in depression and anxiety in cancer patients.