Hippotherapy on autonomic regulation and behavioral symptoms in children with autism

Abstract Background: Autism spectrum disorder (ASD) is frequently associated with autonomic nervous system dysregulation. This study examined whether a structured 6-week hippotherapy program could modulate autonomic regulation and core behavioral symptoms in children with ASD. Methods: Forty-eight children with ASD (aged 9–12 years) were randomized to receive either a 12-session therapist-led hippotherapy intervention (n = 24) or an attention- and time-matched control condition (n = 24). Heart rate variability (HRV) indices, root mean square of successive differences (RMSSD), low-frequency/high-frequency power ratio (LF/HF), and sample entropy (SampEn) were recorded using a Polar OH1 photoplethysmography (PPG) sensor and analyzed after artifact correction. Behavioral symptoms were evaluated with the Gilliam Autism Rating Scale–Second Edition (GARS-2). Linear mixed-effects models tested Group × Time interactions, and the Benjamini–Hochberg false discovery rate (FDR) procedure was applied to control for multiple comparisons. Results: The hippotherapy group demonstrated a significant increase in RMSSD relative to controls (Group × Time contrast: b = 6.17, SE = 1.66, t (90) = 3.71, p < 0.001, Cohen’s d = 0.78). Significant improvements were also observed across all three GARS-2 subscales (all p ≤ 0.002). Although changes in LF/HF ratio and SampEn followed favorable trends, they did not reach statistical significance after FDR correction. Conclusions: The 6-week hippotherapy program produced a robust enhancement in a vagally mediated HRV metric (RMSSD) accompanied by significant behavioral improvements in children with ASD. Observed trends in spectral and entropy measures warrant replication in larger samples with higher-fidelity cardiac recordings.