Probiotics, prebiotics may improve depression symptoms

Probiotics alone or combined with prebiotics may alleviate depression, according to results of a systematic review published in BMJ Nutrition, Prevention & Health.

However, it remains unclear whether they may lessen anxiety.

“The growing appreciation of the interconnectedness between the [gastrointestinal tract] microbiome and the nervous system, combined with the knowledge that pre/probiotics can alter the condition and constitution of the [gastrointestinal tract] microbiome, has highlighted pre/probiotics as potentially therapeutically valuable agents in the treatment of certain psychiatric conditions,” Sanjay Noonan, of Brighton and Sussex Medical School in the U.K., and colleagues wrote. “Among the conditions being investigated are anxiety disorders and depression. The extent to which pre/probiotics might be therapeutically useful (or even viable) in treating anxiety and/or depression is presently unknown, which provides a reasonable rationale for exploring their potential value.”

The investigators conducted the current systematic review of databases and gray literature sites to investigate prebiotics and/or probiotics offered efficacy for treating depression and/or anxiety disorders. They included articles published within the past 15 years, applied pre-determined inclusion/exclusion criteria and used a modified-CASP checklist to determine article quality. Specifically, they focused on quantitative measures of patients who had clinical diagnoses of depression and/or anxiety disorders.

Among 71 reviewed studies, seven met all inclusion criteria. All seven investigated one or more probiotic strain, and four evaluated the effect of combinations of multiple strains. Among the selected studies, 12 probiotic strains were featured, including Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium bifidium. One study examined prebiotic therapy alone, and one study examined combined pre-probiotic treatment.

Results of all included studies showed significant improvement in anxiety symptoms and/or clinically relevant changes in biochemical measures of anxiety and/or depression with probiotic or pre-probiotic use compared with no treatment/placebo or when compared with baseline measurements.

“These preliminary findings suggest continued investigation, on a larger scale and over a longer time period, would be appropriate,” Noonan and colleagues wrote. “However, purely from the information gathered in this review, it is valid to suggest that, for patients with clinically recognized depression, isolate, or adjuvant, prebiotic therapy is unlikely to affect an individual’s experience of their condition in a quantitatively evident way; and that isolate, or adjuvant, probiotic/combined prebiotic–probiotic therapy may offer a quantitatively measurable improvement in parameters relating to depression.

“However, there are inadequate data to suggest anything meaningful to support or refute the use of either pre/probiotic agents (or a combination of both) in patients with clinically recognized anxiety disorders; this would be a useful area to investigate further.”