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