Probiotics taken alone or in combination with prebiotics may help ease depression, according to a systematic review published online in the journal BMJ Nutrition, Prevention & Health.
Probiotics contain bacteria that positively influence the gastrointestinal microbiome, while prebiotics are compounds that promote the flourishing of those bacteria, the researchers explained.
“A bidirectional relationship exists between the brain and the gastrointestinal tract,” researchers wrote. “Whether microbiome influencing therapies could treat psychiatric conditions, including depression and anxiety, is an area of interest.”
The systematic review included 7 studies that investigated at least 1 probiotic strain—some considered multiple probiotic strains—in adults with depression and/or anxiety disorders. Among a total of 12 probiotic strains in the studies, Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum were most common. Combined prebiotic–probiotic treatment was considered in 1 study, while another looked at prebiotic therapy alone.
Every study in the review concluded that probiotic supplements alone or combined with prebiotics may be associated with measurable reductions in depression, researchers reported. In addition, each study showed a significant improvement in anxiety symptoms and/or relevant changes in biochemical measures of anxiety and/or depression with probiotic or combined prebiotic–probiotic use.
Eleven of the 12 probiotic strains investigated were potentially useful, according to the review.
Researchers noted, though, that studies were small and took place over short periods of time. Therefore, they could not draw firm conclusions about overall effects, how long they might last, or unwanted side effects with prolonged use.
Furthermore, data was inadequate to support or refute an effect in people with anxiety disorders.
“These preliminary findings suggest continued investigation, on a larger scale and over a longer time period, would be appropriate,” researchers concluded.
“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.”
Noonan S, Zaveri M, Macaninch E, Martyn K. Food & mood: a review of supplementary prebiotic and probiotic interventions in the treatment of anxiety and depression in adults. BMJ Nutrition, Prevention & Health. 2020 June 9;[Epub ahead of print].