Executive function, balance, and EEG connectivity following hippotherapy in four children with ADHD: An exploratory case-series study

Abstract

Background : This proof-of-concept case series examined the cognitive, motor, and neurophysiological correlates of hippotherapy in four 11-year-old female quadruplets with attention deficit hyperactivity disorder (ADHD). Hippotherapy combines rhythmic equine movement with ground-based human-animal interaction, such as grooming and leading the horse, and was used here to examine whether equine-assisted activity was descriptively associated with changes in executive functioning, balance, and resting-state brain connectivity as a basis for future controlled research rather than a test of treatment efficacy. Methods : Participants completed 16 hippotherapy sessions over 6 weeks. Pre- and post-intervention assessments included executive function (EF) tasks (Stroop Test, Wisconsin Card Sorting Test [WCST], Corsi Block-Tapping Test, and Tower of London), the Berg Balance Scale (BBS), and resting-state electroencephalography (EEG), including power spectral density (PSD), theta-beta ratio (TBR) and theta-delta ratio, and directed phase transfer entropy (dPTE). Given the exploratory design and very small sample, analyses emphasized within-subject change and descriptive effect sizes, using an average-variance formulation of Hedges’ g. Results : Post-intervention improvements were observed across all EF measures: Stroop reaction times decreased across congruent, incongruent, and interference conditions; WCST completed categories increased (from 2.25 to 3.25), and perseverative errors decreased (from 29.75 to 24.25); Corsi Block Span scores improved (from 3.60 to 4.10); and Tower of London move counts decreased (from 68.50 to 62.25). Effect sizes were descriptively large across measures (absolute Hedges’ g range: 1.14–1.70), interpreted cautiously given a sample of four; inferential statistics were not conducted, as n = 4 precludes meaningful interpretation of p-values. Balance also improved (BBS: from 38.50 to 41.00; Hedges’ g = 0.97). EEG analyses descriptively indicated increased delta and theta activities in right frontal and parietal electrodes and elevated posterior alpha power, along with a shift toward stronger frontal-to-posterior delta-band and posterior-to-frontal gamma-band dPTE connectivity. These findings are descriptive only and require statistical validation. Conclusions : As a proof-of-concept case series, this study shows that a multimodal assessment framework can feasibly capture a convergent pattern of behavioral, motor, and neurophysiological changes temporally associated with hippotherapy in these four children with ADHD. Findings should be interpreted cautiously given the limited, non-independent sample of quadruplet siblings and the uncontrolled design and should not be read as evidence of treatment efficacy. Larger, controlled studies, ideally able to separate the horse’s movement from ground-based human-animal interaction, are needed to confirm these observations and clarify the underlying mechanisms.