The present study is aimed at exploring whether positive expectations of receiving a three-week treatment with a probiotic supplement (in fact a placebo) improve symptoms of gastrointestinal distress and promote physical and emotional well-being in healthy individuals with mild gastrointestinal symptoms. At first, a comparison is planned between (1) a classic deceptive placebo manipulation (Deceptive Placebo group, DP), and (2) a control condition (Control group, C), in which no placebo substance will be administered. After the three-week waiting list, the Control group will be invited to take the placebo probiotic pills in an "open-label" fashion (Open Label Placebo, OLP). Specifically, participants will be informed that the pills are inert placebos. An exploratory analysis will help to clarify whether the OLP paradigm leads to significant effects, based on a within-group (C- OLP) and between-group comparison (DP-OLP).
Age between 20 and 65
Individuals with mild gastrointestinal symptoms (e.g., digestive issues, acid reflux, constipation) such that normal every-day activities are not severly compromised.
Individuals with a diagnosis of functional gastrointestinal disorders (e.g., irritable bowel syndrome, ulcerative colitis, chronic inflammatory bowel diseases).
Individuals suffering from neurodegenerative diseases and/or psychiatric conditions
Individuals taking probiotic supplementation at the time of enrollment in the study
Parallel
Placebo probiotic
Other interventionThree-week consumption of placebo probiotic capsules passed off as being actual probiotics
Open-Label Placebo probiotic
Other interventionParticipants of the Control group will be switched to this condition after three weeks and receive placebo probiotic capsules for the following three-weeks of no intervention. Specifically, they will be honestly informed that the capsules are inert placebos.
Control-no treatment
Other interventionFor the first three weeks, the Control group will not be exposed to any intervention.
Change from Baseline in the Gastrointestinal Symptom Rating Scale (GSRS) total score at 3 weeks.
Change from Baseline in the Digestion-Associated Quality Of Life Questionnaire (DQLQ) total score at 3 weeks.
Change from Baseline in Stool Form as assessed by means of the Bristol Stool Scale
The Bristol stool scale is a diagnostic medical tool designed to classify the form of human stool into seven categories.
Change from Baseline in Fatigue Levels as assessed by means of the Multidimensional Fatigue Inventory (MFI-20) at 3 weeks.
Items are scored 1-5, with 10 \[fatigue-\]positively phrased items reverse scored (items 2, 5, 9, 10, 13, 14, 16, 17, 18, 19). In the final score, high scores represent more fatigue.
Change from Baseline in Sleepiness Levels as assessed by means of the The Epworth sleepiness scale at 3 weeks.
Final total score ranges from 0 to 24. Scores from 0 to 10 show average (normal) daytime sleepiness. A result from 11 to 24 indicates excessive (abnormal) daytime sleepiness.
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