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Completed

NCT Number: NCT07216729

The Effects of Probiotic Supplementation on State and Trait Stress, Anxiety, and Depression Symptoms in Stressed Adults

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.

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Key information

Conditions

Anxiety Symptoms Anxiety Disorders Behavior Behavioral Symptoms Depression Depressive Symptoms Mental Disorders Perceived Stress

Age range

18 year–45 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Colorado Boulder, Muenzinger Psychology Building

Boulder, Colorado, 80309, United States

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • age 18 - 45
  • scoring 14+ on the perceived stress scale-10 indicating medium stress or higher
  • ability to provide informed consent
  • willingness not to take probiotic supplements (pills, tablets, oils, etc.) other than the product provided in the clinical study until all study procedures are completed
  • own a smartphone and are willing to receive study materials and complete study procedures by text

Exclusion criteria

  • a history of gastrointestinal discomfort or surgery, urinary incontinence, cancer, toxic shock syndrome, frequent diarrhea, vital signs outside of the acceptable range (i.e., blood pressure >160/100, oral temperature >100°F, pulse >100), heart disease, heart attack, lung/respiratory disease, any pulmonary, cardiovascular, gastrointestinal, hepatic or renal functional abnormality (i.e. a medical diagnosis related to lungs, heart, stomach/intestines, liver, or kidneys), HIV, Hepatitis B, Hepatitis C, bipolar disorder, psychosis, or confirmed or suspected immunosuppression or immunodeficiency
  • current (past month) alcohol or substance abuse or dependence (score of 2+ on the UNCOPE)
  • consistent (e.g., 5x/week or greater) probiotic supplementation within the last month, including probiotic food products such as yogurt
  • receiving antibiotics within the last month
  • receiving medications that interfere with gut motility (opiates, loperamide, stool softeners)
  • use of systemic antibiotics, antifungals, antivirals, or antiparasitics (intravenous, intramuscular, or oral)
  • use of oral, intravenous, intramuscular, nasal or inhaled corticosteroids
  • use of cytokines or cytokine inhibitors
  • use of methotrexate or immunosuppressive cytotoxic agents
  • receiving immunosuppressive drugs/medications or treatment including antineoplastic therapy, post-transplantation immunosuppressive therapy, and/or radiation therapy
  • participation in conflicting interventional research protocol
  • unstable dietary history as defined by major changes in diet during the previous month, where the subject has eliminated or significantly increased a major food group in their diet
  • female who is pregnant or lactating or reports expecting to get pregnant during the course of the study
  • currently involved in the criminal justice system as a prisoner or ward of the state

Treatment and study plan

Lactobacillus reuteri DSM 17938

Dietary Supplement

5 drops (100 million CFUs) daily for 46 days of L. reuteri DSM 17938 in sunflower oil, medium chain triglyceride oil, and silicon dioxide.

Placebo

Other

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.

Primary outcomes

  1. Change from baseline in mean trait perceived stress as assessed by PSS-10

    Time frame: Baseline and the end of treatment at 46 days

    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.

  2. State perceived stress as assessed by adapted PSS-4 using ecological momentary assessment

    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

    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.

Secondary outcomes

  1. Change from baseline in mean trait anxiety symptoms as assessed by GAD-7

    Time frame: Baseline and the end of treatment at 46 days

    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.

  2. State anxiety symptoms as assessed with the SUDS using ecological momentary assessment

    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

    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.

  3. Change from baseline in mean trait depressive symptoms as assessed by the PHQ-8

    Time frame: Baseline and the end of treatment at 46 days

    Patient Health Questionnaire-8 (PHQ-8) administered via REDCap. Possible score range of 0 to 24, with higher scores indicating higher levels of depression.

  4. State depressive symptoms as assessed by SUDS using ecological momentary assessment

    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

    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.

Other outcomes

  1. Side effects as assessed on the final day of supplementation using the GASE

    Time frame: End of treatment at day 46

    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).

Sponsors and collaborators

Lead sponsor

University of Colorado, Boulder

Other

Registry information

Official study title

Evaluating the Effects of Lactobacillus Reuteri DSM 17938 on State and Trait Stress in Stressed Adults

Important dates

Study start
2023
Primary completion
2024
Study completion
2024
First posted
Oct 15, 2025
Registry last updated
Nov 18, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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