The effects of probiotics on depressive symptoms in humans: a systematic review

Abstract

BackgroundPatients suffering from depression experience significant mood, anxiety, and cognitive symptoms. Currently, most antidepressants work by altering neurotransmitter activity in the brain to improve these symptoms. However, in the last decade, research has revealed an extensive bidirectional communication network between the gastrointestinal tract and the central nervous system, referred to as the “gut–brain axis.” Advances in this field have linked psychiatric disorders to changes in the microbiome, making it a potential target for novel antidepressant treatments. The aim of this review is to analyze the current body of research assessing the effects of probiotics, on symptoms of depression in humans.MethodsA systematic search of five databases was performed and study selection was completed using the preferred reporting items for systematic reviews and meta-analyses process.ResultsTen studies met criteria and were analyzed for effects on mood, anxiety, and cognition. Five studies assessed mood symptoms, seven studies assessed anxiety symptoms, and three studies assessed cognition. The majority of the studies found positive results on all measures of depressive symptoms; however, the strain of probiotic, the dosing, and duration of treatment varied widely and no studies assessed sleep.ConclusionThe evidence for probiotics alleviating depressive symptoms is compelling but additional double-blind randomized control trials in clinical populations are warranted to further assess efficacy.

Gutsy Moves: The Amygdala as a Critical Node in Microbiota to Brain Signaling

“…[90,96] Finally, different probiotic strains have been shown to reduce symptoms of anxiety and depression across several studies in clinical and healthy populations. [97,98] While there have also [5,9,10,88,90] Anxiolytic effects, sometimes sex-specific, in mice (light-dark box, elevated-plus maze) [72,113] Anxiolytic effects in mice (open field, defensive marble burying, elevated-plus maze, light-dark box) [91,93] Strain-specific anxiolytic effects in humans (e.g., Beck Anxiety Index, Hospital Anxiety & Depression Scale) and rodents (defensive marble burying, elevated-plus maze, open field) [11,62,133,134] Transplant from humans with depression or comorbid IBS and anxiety increases anxietylike behavior in mice (open field, step-down test, light-dark box) [96,125] Heightened anxiety in rats (open field) [89] Depression Increased depressive-like behavior in mice (forced swim) [90] Increased depressive-like behavior in rats (forced swim) [94] Antidepressant effects in mice and rats (forced swim, tail suspension, learned helplessness after inescapable shock) [91,92] Strain-specific antidepressant effects in humans (e.g. Beck Depression Inventory, Hospital Anxiety & Depression Scale) and rodents (tail suspension test, forced swim, sucrose preference) [11,97,98,133,134] Transplant from depressed human donors induces depressive-like behavior in mice (sucrose preference, forced swim [varied results], tail suspension test) [90,96] Learned fear Impaired fear recall in adult mice [101] Acute administration enhances fear extinction in rodents and exposure therapy in humans, [103,104] reduces fear recall in huma...…”

Astrofood, Priorities and Pandemics: Reflections of an Ultra-Processed Breakfast Program and Contemporary Dysbiotic Drift

“…While still in its infancy, a small but growing list of controlled human studies indicates that oral microbial products (probiotics or nutritional substrates that confer benefit via microbial activity) can improve aspects of mood, cognition, stress and/or anxiety [124][125][126][127]. The mechanisms by which microbes can influence brain development, cognition and behavior include, but are not limited to: direct and indirect microbial interactions with the immune system, enhancement of nutrient bioavailability and neurotransmitter precursors, maintenance of the gastrointestinal lining, reduction of oxidative stress, direct gut microbe-to-brain communication via the vagus nerve which connects the intestinal tract to the emotional centers of the brain, and transformation of dietary phytochemicals into bioactive compounds which subsequently influence mood [21,128].…”

The Effect of Doogh (Yogurt Drink) on Reaction Time and Vigilance- Sleepiness of Healthy Young Adults

“…Consumption of probiotic diary products by those, who have a low mood, has been shown to improve their cognitive performance and mood (20,21). Furthermore, a similar study on the elderly has also displayed a slight improvement in sleep quality, although the effect was not significant compared with the placebo effect and did not change the quality of life (22).…”