Effects of a Placebo Probiotic on Gut Health and General Well-being in Individuals With Mild Gastrointestinal Symptoms

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).