Probiotic Supplement Added to Antidepressant Treatment for Major Depressive Disorder
Tests a probiotic supplement alongside antidepressants in adults with major depressive disorder.
Key facts
- Who runs it
- University Maribor
- Where
- Gornja Radgona, SloveniaSee the site
- Trial code
- Registry title
- Adjunctive Probiotic Therapy in Major Depressive Disorder (ProMOOD)
- Status
- Not yet recruiting
- People taking part
- 200 people, planned
- Started
- Oct 2026
- Expected to end
- Oct 2030
- Type of study
- Interventional, 2 groupsOne group gets a placebo (a dummy treatment), for comparison.
- Treatments tested
- OMNi-BiOTiC® STRESS Repair
- Matched Placebo Powder for Oral Solution
- Record updated
- 31 August 2026
Who can take part
AI summary
From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.
The trial is looking for adults aged 18-65 with depression who already take a stable antidepressant. It tests a probiotic supplement added to their treatment.
- Age
- 18 to 65 years
- Sex
- All sexes can join.
- Disease stage
- Depression confirmed by ICD 11 criteria. Treatment resistant depression and psychotic depression are excluded.
- Earlier treatment
- Must be on the same antidepressant for at least 6 weeks. Must not have used antibiotics recently or probiotics in the past year.
Main reasons for not taking part
- Acute suicidality
- Severe cardiovascular disease
- Pregnancy or breastfeeding
- Substance or alcohol abuse
- Treatment resistant depression or psychotic depression
The registry criteria, word for word
Show all 13 criteriaShow less
Who can take part
- Age 18-65 years
- Confirmed diagnosis of depression according to ICD 11 (International Classification of Diseases) criteria
- Written informed consent
- Stable antidepressant therapy (same medication for at least 6 weeks to ensure stable clinical response)
Who cannot take part
- Severe cardiovascular disease
- Severe neurological or systemic disease
- - Acute suicidality
- Pregnancy or breastfeeding
- Substance/ alcohol abuse
- Recent antibiotic use
- Probiotic use in past year
- Treatment resistant depression
- Psychotic depression
Check if you might fit
Answer for yourself. This is not a decision: only the study team can say whether you can take part.
- Are you between 18 and 65 years old?
Where in Slovenia
- Zdravstveni dom Gornja RadgonaGornja Radgona, SloveniaContact: Psihiatrična ambulantaNo longer taking part
About the trial
What the trial wants to find out
A double-blind, randomized controlled trial (RCT) aimed at evaluating the efficacy of probiotic supplementation in patients undergoing concurrent antidepressant therapy.
Read full original descriptionShow less
The study will also assess gut microbiome composition and function, and correlate microbiome changes with clinical and psychological outcomes.
Participants will be evaluated by a psychiatrist/clinician, alongside standardized psychological assessments at:
* Baseline (inclusion) * Week 4 * Week 12
The following validated instruments will be used:
* HAM-D - Hamilton Depression Rating Scale (clinician-rated depression severity) * BDI - Beck Depression Inventory (self-reported severity of depression) * PSS - Perceived Stress Scale (self-reported stress perception)
Inclusion Criteria
* Age 18-65 years * Confirmed diagnosis of depression according to ICD 11 (International Classification of Diseases) criteria * Written informed consent * Stable antidepressant therapy (same medication for at least 6 weeks to ensure stable clinical response)
Exclusion Criteria
* Acute suicidality * Severe cardiovascular disease * Pregnancy or breastfeeding * Substance/ alcohol abuse * Severe neurological or systemic disease * Recent antibiotic use * Probiotic use in past year * Treatment resistant depression * Psychotic depression
Sample Size
* Initial recruitment target: 150-200 participants * Expected dropout rate: approximately 50%, based on similar studies * Final expected sample size: ~100 participants * Sample size calculation based on Nikolova et al., 2023.
Primary outcome Change in Hamilton Depression Rating Scale (HAM-D-17) score from baseline to Week 12.
Secondary outcomes Change in Beck Depression Inventory-II (BDI-II) score from baseline to Week 12. Change in Perceived Stress Scale (PSS-10) score from baseline to Week 12. Changes in gut microbiome composition and diversity (α-diversity, β-diversity and relative abundance of bacterial taxa) between baseline and Week 12.
Safety and tolerability of probiotic supplementation, assessed by adverse events and treatment discontinuation.
Intervention:
OmniBiotic Stress Repair
Microbiome Analysis Subgroup
Stool samples will be collected at:
* Baseline * 1 month * 3 months Analysis will follow methodologies similar to Mörkl S et al. (2025).
Remark: Additional sampling at 1 week (as done in the referenced study) is considered unnecessary, as it falls outside routine clinical monitoring.
Antidepressant Strategy
* Include patients receiving SSRI (Selective Serotonin Reuptake Inhibitors) and possibly SNRI (Serotonin-Norepinephrine Reuptake Inhibitors) * Advantage: broader applicability * Limitation: increased variability
The 2 groups in the trial
- OMNi-BiOTiC STRESS RepairTreatment being tested
Stable antidepressant therapy plus OMNi-BiOTiC STRESS Repair for 12 weeks
- Control groupPlacebo, for comparison
Treatment: Matched Placebo Powder for Oral Solution
Questions to ask the study team
- How often do I need to come in, and for how long each time?
- Are travel costs paid?
- Can I keep my own doctor?
- What happens if I want to stop?
Contact the study team: see the registry record → Contacts and Locations
Print a page for my doctorData and sources
- Registry record
- Listed on ClinicalTrials.gov.
- Official title
- Adjunctive Probiotic Therapy in Major Depressive Disorder: A Randomized Controlled Trial (ProMOOD)
- Plain-language title
- Probiotic Supplement Added to Antidepressant Treatment for Major Depressive DisorderGenerated from the registry record. The registry title is the official one.
- AI summary
- From the trial's eligibility criteria. Read by machine on 12 November 2026.
- Fit questions
- Built from NCT07786285, who can take part
- Record updated
- 31 August 2026