Abstract
Recent years have seen a rapid increase in the use of gut microbiota-targeting interventions, such as probiotics, for the treatment of psychiatric disorders. The objective of this update review was to evaluate all randomised controlled clinical trial evidence on the efficacy of probiotics for clinical depression. Cochrane guidelines for updated reviews were followed. By searching PubMed and Web of Science databases, we identified 546 new records since our previous review. A total of seven studies met selection criteria, capturing 404 people with depression. A random effects meta-analysis using treatment type (stand-alone vs. adjunctive) as subgroup was performed. The results demonstrated that probiotics are effective in reducing depressive symptoms when administered in addition to antidepressants (SMD = 0.83, 95%CI 0.49–1.17), however, they do not seem to offer significant benefits when used as stand-alone treatment (SMD = −0.02, 95%CI −0.34–0.30). Potential mechanisms of action may be via increases in brain-derived neurotrophic factor (BDNF) and decreases in C-reactive protein (CRP), although limited evidence is available at present. This review offers stronger evidence to support the clinical use of probiotics in depressed populations and provides an insight into the mode of administration more likely to yield antidepressant effects.
Highlights
Major depressive disorder (MDD) is a common, complex, and heterogeneous illness that is characterized by persistent low mood and anhedonia, and a combination of sleep disturbances, changes in appetite, feelings of worthlessness or guilt, poor concentration, and suicidal ideation [1]
We aimed to evaluate all up-to-date evidence from randomised controlled trials (RCTs) on the efficacy of probiotics as a treatment for depressive symptoms among people with clinical depression without another primary diagnosis
While other reviews have captured larger numbers of studies, these have included healthy volunteers and populations with a primary condition other than depression, as well as no restrictions on trial design. We considered this approach to be of limited value in determining the clinical utility of probiotics for the treatment of depression, and restricted our inclusion criteria to only capture RCT designs and populations meeting a clinical cut-off for depression with no other primary diagnosis
Summary
Major depressive disorder (MDD) is a common, complex, and heterogeneous illness that is characterized by persistent low mood and anhedonia, and a combination of sleep disturbances, changes in appetite, feelings of worthlessness or guilt, poor concentration, and suicidal ideation [1]. It is estimated that more than 264 million people suffer from MDD globally, and there are approximately 800,000 suicide deaths yearly linked to depression [3]. It has been estimated that up to 60% of patients with MDD experience some degree of non-response to the wide range of pharmacological treatments [4], which predominantly target monoamine dysregulation in the brain. This suggests that there are other mechanisms implicated in the aetiology of depression, and abnormalities in the neuroendocrine, immune, neurotrophic, and metabolic systems have been identified [5]. There has been a surge in novel treatment paradigms targeting the gut microbiota in depressive disorders, including probiotics, prebiotics, nutraceuticals, and various dietary interventions
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