An interventional study of Lactobacillus reuteri DSM 17938 and Placebo in Anxiety Symptoms, Perceived Stress and Depressive Symptoms, sponsored by University of Colorado, Boulder. Completed at 1 site in United States. Open to participants aged 18 Years to 45 Years. Per ClinicalTrials.gov, last updated 2025-11-18.
Sponsored by University of Colorado, Boulder · Not applicable, Interventional, and Supportive care
The goal of this randomized controlled trial is to learn if supplementation with the probiotic Lactobacillus reuteri DSM 17938 can reduce levels of trait and state perceived stress, anxiety, and depressive symptoms compared to a placebo in a population of stressed adults ages 18-45. This study also investigates several evidence-based moderators of treatment effects, evaluates whether the probiotic caused side effects, and evaluates whether effects endured at 1-month post-supplementation.
4,868 studies on the registry are indexed under Anxiety Disorders; 1,390 are open to participants now.
This study's enrollment of 150 is above the median of 80 across 4,174 interventional studies indexed under Anxiety Disorders.
Browse Anxiety Disorders studies →University of Colorado, Boulder is the lead sponsor of 86 studies on the registry; 20 are open to participants now.
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Exclusion Criteria:
5 drops daily (100 million colony-forming units) for 46 days of Lactobacillus reuteri DSM 17938 in sunflower oil, medium chain triglyceride oil, and silicon dioxide.
Dietary Supplement: Lactobacillus reuteri DSM 17938
5 drops daily for 46 days of a placebo consisting of the inactive ingredients from the probiotic supplement, specifically sunflower oil, medium chain triglyceride oil, and silicon dioxide.
Other: Placebo
5 drops (100 million CFUs) daily for 46 days of L. reuteri DSM 17938 in sunflower oil, medium chain triglyceride oil, and silicon dioxide.
5 drops daily for 46 days of placebo consisting of inactive ingredients from probiotic supplement, specifically sunflower oil, medium chain triglyceride oil, and silicon dioxide.
Change from baseline in mean trait perceived stress as assessed by PSS-10
Perceived stress scale-10 (PSS-10) administered via REDCap. Possible score range of 0 to 40, with 0-13 considered low stress, 14-26 moderate stress, and 27-40 high stress.
Time frame: Baseline and the end of treatment at 46 days
State perceived stress as assessed by adapted PSS-4 using ecological momentary assessment
Perceived stress scale-4 (PSS-4) administered via REDCap and adapted for state measurement. The investigators adapted this measure for state stress by asking participants to rate the intensity of perceived stress they were experiencing in the moment, as opposed to the frequency with which they experienced perceived stress over the past month. Possible score range of 0 to 16, with higher scores indicating higher levels of state stress.
Time frame: Five times per day (hourly, 12-7pm, sent via text with a 15 minute response window) during the last 5 days of supplementation, days 42 to 46, when the investigators expect participants to have reached maximum benefit
Change from baseline in mean trait anxiety symptoms as assessed by GAD-7
Generalized Anxiety Disorder-7 scale (GAD-7) administered via REDCap. Possible score range of 0 to 21, with higher scores indicating higher levels of anxiety symptoms.
Time frame: Baseline and the end of treatment at 46 days
State anxiety symptoms as assessed with the SUDS using ecological momentary assessment
Subjective units of distress scale (SUDS) administered via REDCap. Possible score range of 0 to 100, with higher scores indicating higher levels of state anxiety.
Time frame: Five times per day (hourly, 12-7pm, sent via text with a 15 minute response window) during the last 5 days of supplementation, days 42 to 46, when the investigators expect participants to have reached maximum benefit
Change from baseline in mean trait depressive symptoms as assessed by the PHQ-8
Patient Health Questionnaire-8 (PHQ-8) administered via REDCap. Possible score range of 0 to 24, with higher scores indicating higher levels of depression.
Time frame: Baseline and the end of treatment at 46 days
State depressive symptoms as assessed by SUDS using ecological momentary assessment
Subjective Units of Distress Scale (SUDS) administered via REDCap. Possible score range of 0 to 100, with higher scores indicating higher levels of state depression.
Time frame: Five times per day (hourly, 12-7pm, sent via text with a 15 minute response window) during the last 5 days of supplementation, days 42 to 46, when the investigators expect participants to have reached maximum benefit
Side effects as assessed on the final day of supplementation using the GASE
Generic Assessment of Side Effects (GASE), excluding the question assessing suicidality and administered on REDCap. This measure assesses 35 of the most common subjective side effects of clinical trials (e.g., nausea), and asks participants to rate whether they experienced each complaint on a scale from 0 ("not present") to 3 ("severe"). If they endorsed experiencing a side effect (score of 1+), participants were then asked whether the complaint related to the probiotic (yes/no).
Time frame: End of treatment at day 46
Plan to share: Yes — Deidentified individual participant data (IPD) will be shared with other researchers in our lab to conduct secondary analyses. Data sharing will ensure protection of participant confidentiality.
Supporting information: Study protocol, Sap, Analytic code
This study is completed, as verified in Nov 2025. You cannot join it, but the record below documents what was studied.
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University of Colorado, Boulder