What doe they mean experiential when talking about behavior and health?

Treatment studies: If a condition has few if any accepted treatments, physicians & therapists will get together & come up with ideas about things that could help.They devise a protocol, or list, of the type of things they want to try & send it to a review board (irb)that examines it for need & patient safety. If approved, they enroll patients in a trial to see if it helps. That's how treatments come about.