PB-18 Probiotic for Mild to Moderate Depression

The goal of this clinical trial is to learn if Bifidobacterium PB-18 can treat mild to moderate depressive disorder in adults aged 18 to 65 years who are not taking antidepressants or other psychotropic medications during the study. It will also learn about the safety of Bifidobacterium PB-18 and explore its potential effects on the gut-brain axis. The main questions it aims to answer are: Does Bifidobacterium PB-18 increase the response rate at Week 8, defined as a reduction of at least 50% from baseline in the 17-item Hamilton Depression Rating Scale (HAMD-17)? What adverse events occur in participants receiving Bifidobacterium PB-18? How do gut microbiota, metabolite profiles, and related biological markers change after treatment with Bifidobacterium PB-18? Researchers will compare Bifidobacterium PB-18 with a placebo, a look-alike powder that does not contain PB-18, to see if Bifidobacterium PB-18 improves depressive symptoms. Participants will: Be randomly assigned to receive Bifidobacterium PB-18 or placebo in a 1:1 ratio Take the assigned study product once daily for 8 weeks Visit the study site at baseline, Week 4, and Week 8 for symptom and safety assessments Complete study questionnaires, including HAMD-17, HAMA, PSQI, and CBCT Provide blood and stool samples at baseline and Week 8 for exploratory biological analyses

NCT Number	NCT07562516
Lead Sponsor	First Affiliated Hospital of Zhejiang University
Conditions	Depressive Disorder
Enrollment	88 participants
Start Date	2026-05-05
Primary Completion	2027-01-31 (estimated)
Study Completion	2027-04-30 (estimated)
Updated on ClinicalTrials.gov	2026-05-07