Inclusion Criteria:  REN users in the U.S.  Exclusion Criteria:  Cohort 1 REN treatments that were shorter than 20 minutes or did not have a report of pain level.  Cohort 2 Treatments in which medications were taken within 2 hours from REN treatment. Users that had less than 2 REN treatments.  Cohort 3 REN treatments that were shorter than 20 minutes  Cohort 4 All REN sessions, regardless of duration or medication intake.