Experience after Floatation-REST: relaxation during floating mediates the afterglow effect

The term “afterglow“ was first used to describe the heightened mood, relaxation, and overall sense of tranquility reported by individuals hours or even days after the use of psychedelics, after their most immediate effects had dissipated. The use of the word “afterglow” was then extended to similar states achieved after other altered-state experiences. Even though the afterglow effect is widely reported anecdotally, not much quantitative research has been undertaken on it and none at all explicitly related to Floatation-REST (Reduced Environmental Stimulation Technique). In Floatation-REST an individual floats almost weightlessly on the surface of thermoneutral, supersaturated salt water in a quiet, dark tank. Using a within-subject crossover design, 34 healthy subjects were randomized to 60 min of Floatation-REST or 60 min of Bed-REST, a control condition where one lies supine on a waterbed in a dark, quiet room. We assessed the experience during the REST conditions as well as regarding the alleged afterglow effect following a 10-minute period of silence after exposure to the conditions. Floatation-REST led to weaker body boundaries, stronger time distortion, and more relaxation, as experienced during the conditions. After Floatation-REST exposure, individuals reported a stronger feeling of afterglow as measured with an afterglow inventory, more state mindfulness, and more interoceptive awareness. A mediation analysis revealed that the relaxation experienced during Floatation-REST completely mediates the afterglow effect: The feeling of afterglow follows from a specific increase in relaxation during floating. Our findings support prior research on psychedelics by showing that Floatation-REST produces qualitatively similar effects. This very first study sets the ground for future studies on the afterglow effect for longer time increments after altered-state experiences.