Probiotics Alone or With Prebiotics Tied to Reduced Depression Symptoms

By Lisa Rappaport

July 27, 2020

(Reuters Health) - People who take probiotics alone or in combination with prebiotics may see a reduction in depression symptoms, a research review suggests.

Researchers examined data from seven previously published studies that assessed the impact of at least one probiotic strain on adults with symptoms of anxiety and/or depression. Four of the studies in the analysis looked at combinations of multiple strains of probiotics or prebiotics.

Across all the studies, researchers looked at 12 probiotic strains including Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidium. All studies found a significant reduction or improvement in anxiety symptoms or clinically relevant changes in biochemical measures of anxiety or depression with probiotics alone or in combination with prebiotics as compared with placebo or no treatment.

Of the 12 different probiotics investigated, 11 were potentially useful, the review authors report in BMJ Nutrition, Prevention & Health. However, the study team notes that all the included studies were too small and brief to draw broad conclusions about probiotics or prebiotics for the prevention or treatment of mood disorders.

"The results of this study show that it is promising and probably worthwhile to further look into the effects of probiotics on depression," said Dr. Esther Aarts, of the Donders Centre for Cognitive Neuroimaging at Radboud University in Nijmegen, The Netherlands.

"However, it is too early to give any clear clinical advice," Dr. Aarts, who wasn't involved in the study, said by email. "The number of studies is too low so far, the type of probiotic strain - or, combination of strains - that is most effective is unclear, as is the dose and duration of intervention."

The idea that probiotics can decrease self-reported depressive symptoms more than depression is in line with previous research reviews demonstrating a reduction in depressive symptoms, Dr. Aarts said. These previous reviews indicated a reduced risk for depression by using probiotics, whereas the current study might indicate a therapeutic effect of probiotics in depression, Dr. Aarts said.

It's possible that probiotics may help reduce the production of inflammatory chemicals, such as cytokines, that play a role in conditions such as inflammatory bowel disease, the study team writes.

Probiotics or prebiotics might also help influence the activity of tryptophan, which plays a role in mood disorders, the study team also speculates.

"The current study found little evidence for a role of immune responses and mixed support for the role of tryptophan," said Richard Liu, director of suicide research at Massachusetts General Hospital and Harvard Medical School in Boston.

"It suggests that more research needs to be done in this area," Liu, who wasn't involved in the study, said by email. "These findings matter for clinical care because if probiotics are effective, they have potential to become a new treatment for anxiety and depression with little risk of side effects and no risk of addiction."

SOURCE: BMJ Nutrition, Prevention & Health, online July 6, 2020.