A total of 72 randomized controlled trials involving 3,319 intervention and 2,778 control participants were analyzed.
, , and may significantly reduce depression scores compared to placebo (effect size = −0.53).
Anxiety scores could also be significantly reduced with these interventions (effect size = −0.44).
Probiotics are associated with improved sleep quality (effect size = −0.39).
Subgroup analyses suggest that the effectiveness of these treatments varies by population, intervention duration, and type of probiotic.
High heterogeneity and limited quality of the included studies indicate a need for further large-scale and high-quality trials.
Simplified
BACKGROUND: With the growing recognition of the limitations associated with conventional treatments for anxiety and depression, there has been increasing interest in alternative and adjunct therapies, particularly , , and . However, current research results regarding their efficacy in treating anxiety, depression, and sleep have been inconsistent.
METHODS: A systematic literature search for randomized controlled trials (RCTs) was conducted in PubMed, Web of Science, and Embase from inception to October 2023, updated in March 2025. The included studies involved individuals with anxiety and depression disorders, or chronic disease patients/healthy populations presenting with depressive or anxiety symptoms. Two researchers independently screened and extracted data. The Cochrane risk of bias tool was used to evaluate the quality of the included studies. Data synthesis and subgroup analyses were performed in Review Manager 5.3 and Stata 15.0 software. The anxiety, depression, and sleep scores were calculated by the standard mean difference () and 95% confidence intervals (s). SMD CI
RESULTS: A total of 72 RCTs were included (3,319 intervention and 2,778 control participants). Among these, researchers examined depression in 63 studies (2,880 and 2,493 participants) and anxiety in 49 studies (2,124 and 1,788 participants) using probiotics/prebiotics/synbiotics interventions, while 12 studies (411 and 378 participants) examined sleep using probiotic interventions. The meta-analysis demonstrated significant reductions compared to placebo in depression ( = − 0.53, 95%: −0.67 to − 0.39, Z = 7.33, < 0.001) and anxiety ( = − 0.44, 95%: −0.59 to − 0.28, < 0.001). Additionally, probiotics were shown to improve sleep quality ( = − 0.39, 95%: −0.53 to − 0.25, < 0.001). Subgroup analyses indicated that both probiotics, prebiotics, and synbiotics independently alleviated anxiety and depression. The impact of probiotics varied by population, intervention duration, and probiotic types. SMD CI P SMD CI P SMD CI P
CONCLUSION: These findings suggest that probiotics, prebiotics, and synbiotics offer promising adjunctive treatments for anxiety, depression, and sleep disturbances. However, given the high heterogeneity and limited methodological quality of the included studies, further large-scale and high-quality RCTs with long-term follow-up are needed to further validate these outcomes.
REGISTRATION: The protocol was registered on PROSPERO (Registration number: CRD42024563862).
CLINICAL TRIAL NUMBER: Not applicable.
SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12888-025-07644-z.
Key numbers
−0.53
Reduction in Depression Scores
Effect size from 63 studies on depression outcomes.
−0.44
Reduction in Anxiety Scores
Effect size from 49 studies on anxiety outcomes.
−0.39
Improvement in Sleep Quality
Effect size from 12 studies focused on sleep outcomes.
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Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.
