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Effects of Incorporating Horses into Occupational Therapy on Adrenocortical and Sympathetic Nervous System Reactivity and Regulation in Autistic Children: A Randomized Controlled Trial.
Abstract: The study prospectively investigated adrenocortical and autonomic nervous system reactivity and regulation as autistic children participated in a randomized controlled trial of occupational therapy in an equine environment (OT-Equine). Methods: Autistic children (n = 72, ages 6-11 yrs) were randomly assigned for 10 weeks to OT-Equine or clinic-based occupational therapy (OT-Clinic). Saliva samples (later assayed for cortisol and alpha-amylase, [sAA]) were collected before (pre-session), during (within-session), immediately after (post-session), and 20-minutes after (post-session + 20) each 1-hour weekly session. Data were analyzed with a generalized linear mixed-effects model. Results: Across the 10 sessions, pre-session sAA significantly increased (exp(b) = 1.02 per week, p < 0.05). Within sessions, sAA increased (exp(b) = 1.22; p 0.05). Within session, however, cortisol concentrations decreased from pre- to post- and post-session + 20, with greater reductions among OT-Equine participants (exp(b) = 0.77; p < 0.01). Changes in cortisol were associated with improved treatment outcomes. Conclusions: The pattern of reactivity and recovery in sAA suggests that children experienced autonomic/sympathetic arousal in response to therapy sessions, perhaps associated with excitement and positive affect. Moreover, stable pre-session cortisol concentrations across sessions for both groups, and declining cortisol concentrations within sessions for the OT-Equine group, suggests OT-Equine participants also held subjective experiences characterized by familiarity and low levels of distress. Taken together, findings suggest the integration of horses into occupational therapy for autistic children creates an exciting positive therapeutic environment, associated with improved treatment outcomes. The study was registered as a clinical trial at clinicaltrials.gov (NCT05846932, registered April 26, 2023).
© 2026. The Author(s).
Publication Date: 2026-10-10 PubMed ID: 42859339PubMed Central: 3270695DOI: 10.1007/s10803-026-07540-9Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
Overview
- This study examined how including horses in occupational therapy sessions affects stress and nervous system responses in children with autism, comparing these responses to traditional clinic-based therapy.
Purpose and Background
- The research aimed to assess the physiological effects—specifically, the body’s stress hormones and autonomic nervous system activity—of occupational therapy conducted in an equine (horse-involved) environment versus a traditional clinic setting.
- Understanding these effects is important to optimize therapeutic approaches that support emotional regulation and engagement in autistic children.
Participants and Study Design
- 72 autistic children aged between 6 and 11 years participated in the study.
- Participants were randomly assigned to one of two groups for ten weeks:
- OT-Equine group: Occupational therapy involving activities with horses.
- OT-Clinic group: Traditional clinic-based occupational therapy without horses.
- The randomized controlled trial design helps ensure that differences in outcomes are likely due to the therapy type rather than other factors.
Methods and Measurements
- Therapy sessions lasted one hour each week for ten weeks.
- Saliva samples were collected at four distinct points during each session:
- Pre-session (before therapy)
- Within-session (during therapy)
- Immediately post-session (right after therapy)
- Post-session + 20 minutes (20 minutes after therapy ended)
- Saliva was analyzed for:
- Cortisol—a hormone indicative of hypothalamic-pituitary-adrenal (HPA) axis activity and stress level.
- Alpha-amylase (sAA)—an enzyme marker reflecting sympathetic nervous system (part of the autonomic nervous system) arousal.
- A generalized linear mixed-effects model was used to analyze changes and differences over time and between groups.
Key Findings on Sympathetic Nervous System Activity (sAA)
- Pre-session sAA levels increased slightly across the ten weeks, indicating a mild increase in baseline sympathetic activation over time.
- During therapy sessions, sAA levels rose significantly, suggesting sympathetic arousal, which could be linked to excitement or increased engagement.
- sAA levels returned to baseline within 20 minutes after sessions, indicating recovery from sympathetic activation.
- No significant differences were found between the OT-Equine and OT-Clinic groups regarding sAA changes, implying that both therapies elicited similar sympathetic nervous system responses.
Key Findings on HPA Axis Activity (Cortisol)
- Pre-session cortisol levels remained stable over the ten weeks for both groups, suggesting no change in baseline HPA axis stress levels prior to therapy sessions.
- Within sessions, cortisol levels decreased from pre-session to immediately post-session and remained lower 20 minutes post-session.
- The OT-Equine group showed greater declines in cortisol during sessions compared to the OT-Clinic group.
- These greater reductions in cortisol were correlated with improved treatment outcomes in the OT-Equine group, indicating that decreased stress hormone levels during therapy relate to better results.
Interpretation and Conclusions
- The increase and recovery pattern of sAA during therapy suggests that children experience sympathetic activation, probably reflecting positive excitement or engagement, not distress.
- Stable pre-session cortisol levels indicate the children were not experiencing increasing anticipatory stress across therapy sessions in either treatment.
- Greater within-session cortisol reductions in the OT-Equine group imply that this therapy enabled children to experience a relaxing or familiar environment with low distress during sessions.
- The incorporation of horses in occupational therapy appears to create an environment that is both stimulating (activating the sympathetic nervous system in a positive way) and calming (lowering cortisol), contributing to enhanced therapeutic outcomes.
- This suggests a unique benefit of equine-assisted occupational therapy for autistic children, supporting emotional regulation and engagement more effectively than clinic-based therapy alone.
Trial Registration
- The study was registered at clinicaltrials.gov with identifier NCT05846932 on April 26, 2023, ensuring transparency and adherence to clinical trial standards.
Cite This Article
APA
Rankins EM, Aichele S, Granger DA, Hepburn S, Gabriels R, Schmid AA, Peters BC.
(2026).
Effects of Incorporating Horses into Occupational Therapy on Adrenocortical and Sympathetic Nervous System Reactivity and Regulation in Autistic Children: A Randomized Controlled Trial.
J Autism Dev Disord.
https://doi.org/10.1007/s10803-026-07540-9 Publication
Researcher Affiliations
- Temple Grandin Equine Center, Department of Animal Sciences, Colorado State University, Spur Campus, 4817 National Western Dr, Denver, CO, 80216, USA.
- Department of Human Development and Family Studies, Colorado State University, Fort Collins, CO, USA.
- Department of Psychology, University of California at Irvine, Irvine, CA, USA.
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Human Development and Family Studies, Colorado State University, Fort Collins, CO, USA.
- University of Colorado Anschutz Medical Campus and the Children's Hospital Colorado, Aurora, CO, USA.
- Department of Occupational Therapy, Colorado State University, Fort Collins, CO, USA.
- Temple Grandin Equine Center, Department of Animal Sciences, Colorado State University, Spur Campus, 4817 National Western Dr, Denver, CO, 80216, USA. caiti.peters@colostate.edu.
- Department of Occupational Therapy, Colorado State University, Fort Collins, CO, USA. caiti.peters@colostate.edu.
Grant Funding
- R21HD109957 / Eunice Kennedy Shriver National Institute of Child Health and Human Development
- BuildStrong Foundation / BuildStrong Foundation
- Carl and Caroline Swanson Foundation / Carl and Caroline Swanson Foundation
Conflict of Interest Statement
Declarations. Competing Interests: In the interest of full disclosure, DAG is the founder and chief scientific and strategy advisor at Salimetrics LLC and Salivabio LLC and those relationships are managed by the policies of the committees on conflict of interest at the Johns Hopkins University School of Medicine and the University of California at Irvine. No other authors have competing interests to declare that are relevant to the content of this article. Ethical Approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. All procedures were approved by the Colorado State University Institutional Review Board (Approved March 8, 2023, Protocol #4049) and Institutional Care and Use Committee (Approved January 3, 2023, Protocol #4071). Parents of children in the study provided informed consent and children provided informed assent before participating in the study.
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