Sanjay Noonan, Meena Zaveri, Elaine Macaninch, Kathy Martyn
Journal: BMJ nutrition, prevention & health 2020;3(2):351-362
PMID: 33521545
The gut microbiome plays an important role in the bidirectional communication between the gastrointestinal tract and the brain. In this light, psychiatric disorders may be influenced by the gut microbiome, and pre/probiotics show potential as therapeutic agents in the clinical setting. The aim of this review is to investigate the efficacy of pre/probiotics in quantitatively reducing negative symptoms associated with anxiety and depression. This review included seven studies and found probiotic or combined pre/probiotic use demonstrated a significant quantitatively evident improvement in symptoms in depression. Prebiotics alone did not have a significant therapeutic impact. Based on these results, the authors suggest combined pre/probiotics, or probiotics alone, may be useful as an adjunct therapy when treating patients with depression, especially among patients with existing co-morbidities that impact gastrointestinal health. These results warrant further investigation to identify specific biochemical changes that accompany therapeutic outcomes.
BACKGROUND
A bidirectional relationship exists between the brain and the gastrointestinal tract. Foods containing bacteria that positively influence the gastrointestinal microbiome are termed, probiotics; compounds that promote the flourishing of these bacteria are termed, prebiotics. Whether microbiome influencing therapies could treat psychiatric conditions, including depression and anxiety, is an area of interest. Presently, no established consensus for such treatment exists.
METHODS
This systematic review analyses databases and grey literature sites to investigate pre and/or probiotics as treatments for depression and/or anxiety disorders. Articles included are from within 15 years. Pre-determined inclusion exclusion criteria were applied, and articles were appraised for their quality using a modified-CASP checklist. This review focuses specifically on quantitative measures from patients with clinical diagnoses of depression and/or anxiety disorders.
RESULTS
7 studies were identified. All demonstrated significant improvements in one or more of the outcomes measuring the of effect taking pre/probiotics compared with no treatment/placebo, or when compared to baseline measurements.
DISCUSSION
Our review suggests utilising pre/probiotic may be a potentially useful adjunctive treatment. Furthermore, patients with certain co-morbidities, such as IBS, might experience greater benefits from such treatments, given that pre/probiotic are useful treatments for other conditions that were not the primary focus of this discourse. Our results are limited by several factors: sample sizes (adequate, though not robust); short study durations, long-term effects and propensity for remission undetermined.
CONCLUSION
Our results affirm that pre/probiotic therapy warrants further investigation. Efforts should aim to elucidate whether the perceived efficacy of pre/probiotic therapy in depression and/or anxiety disorders can be replicated in larger test populations, and whether such effects are maintained through continued treatment, or post cessation. Interventions should also be investigated in isolation, not combination, to ascertain where the observed effects are attributable to. Efforts to produce mechanistic explanations for such effect should be a priority.
© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.
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