Influence of rituals on open-label placebo effect in healthy volunteers

Open-label placebo administration (2 placebo pills per day to take every morning, with or without a ritual procedure to perform when taking the pills) for 6 days compared to a no treatment control condition. Adherence will be assessed via self-report at follow-up after completion of the course of placebo pills (day 6). Participants in the 'placebo plus ritual' group will be given a ritual procedure to follow every time they take the pills (A sequence of actions to perform, including shaking the capsules, blowing on them, gently tapping three times with one's hand on their forehead, chest and abdomen- see below for the complete procedure). Participants in the 'placebo only' group will be told to take two pills every day at the same time, without further instructions. All participants will be provided with information about the placebo effect following the talking points outlined by Kaptchuk and colleagues (2010) - namely that placebos are powerful, can produce an automatic healing response, that positive expectations are not necessary but keeping an open mind is important, and that taking pills faithfully (i.e. adherence) is critical. Information and instructions will be provided to both groups during an initial half hour face-to-face research session. Information provision will take approximately 10 minutes. At the end of this session, after completing a baseline assessment, participants will be given lactose-filled vegetarian gelatin placebo capsules to take every morning for the next 6 days and instructions on how to take them. Ritual procedure (approx. 90 seconds to complete): - Wash your hands up to your wrists; - Get the container and some water to drink; - Find a quiet and comfortable place; - Open the container and pick an orange capsule and a pink capsule; - Hold them in the palm of your non-dominant hand, keeping the hand open; - Close both hands together, holding the capsules; - Shake your hands lightly three times; - Close your eyes and gently blow into your hands, on the capsules; - Open your eyes and release your hands; - Pick the orange capsule and take it with some water; - Take a deep inhale and slowly exhale; - Pick the pink capsule and take it with some water; - Close your eyes and with the index and middle fingers of your dominant hand: • Tap your forehead three times; • Tap your heart three times; • Tap your abdomen three times; - Merge your hands in front of your chest and bow your head; - Lift up.