Anna Naber Anna Naber L. Kreuzer L. Kreuzer Roswitha Zink Roswitha Zink Eva Millesi Eva Millesi Rupert Palme Rupert Palme Karin Hediger Karin Hediger Lisa Glenk Lisa Glenk Elsevier 2025 This exploratory study aimed to analyse physiological interaction processes in equine-assisted-therapy (EAT) between client, therapy horse and therapist.We measured heart rate (HR), heart rate variability (HRV) and cortisol levels before, during and after a standardized therapy session and a control condition in one therapist, four therapy horses and ten female clients in emerging adulthood (Mn = 21.8 years, SD = 3.39). The clients were diagnosed with mild (N = 5) to moderate (N = 5) intellectual disability (ID).There was no significant change in the client's HR, HRV and cortisol levels during an EAT session. No difference was observed between therapy sessions with or without a therapy horse, except during the challenge phase of the EAT protocol, where clients had a significantly lower HR when interacting with the therapy horse. HR between therapist and client correlated significantly, as well as between therapist and horse. This effect was greater when therapists interacted with a familiar horse. Clients' and horses' HRs also correlated, but only when the horse was the clients' familiar and preferred horse.These results indicate that relationship intensity is an important factor for the synchronization process. Moreover, the inclusion of horses in a therapeutic setting can lead to a decreased HR in young adults with intellectual disability while mastering a challenge. Future research should investigate this potential benefit of EAT, considering the reciprocal influences and the relationship between client, therapist and horse. PDFDocument eng 2025-04-28T09:32:52.127570Z 2025 Female Hydrocortisone Analysis Hydrocortisone Metabolism Equine-Assisted Therapy Methods Humans Animals Heart Rate Physiology Horses Saliva Chemistry Young Adult Adult Arousal Physiology Intellectual Disability Therapy Male 2720530 b application/pdf http://creativecommons.org/licenses/by-nc-nd/4.0/