Heart Rate Variability in Children and Adolescents with Autism, ADHD and Co-occurring Autism and ADHD, During Passive and Active Experimental Conditions.
Alessio Bellato, Iti Arora, Puja Kochhar and 3 others
PMID 34716841WHAT IT FOUND
Children with ADHD showed signs of low arousal at rest, while those with autism showed high arousal during tasks.
Those with both conditions displayed both patterns. Autonomic profiles did not match diagnostic labels alone, suggesting physiological differences cut across diagnoses.
Key findings
01Children with ADHD had lower sympathetic activity (hypo-arousal) at rest and during passive tasks compared to those without ADHD.
02Children with autism had lower parasympathetic activity (hyper-arousal) during active cognitive tasks compared to those without autism.
03Cluster analysis revealed two physiological subgroups: a 'Low-CSI' group (mostly ADHD-only) and a 'Low-CVI' group (mixed autism/ADHD), with the latter showing more severe social difficulties and anxiety.
STILL TO COME
How it was doneWhat they foundWhat it means for OTsWhat it means for SLPs
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What it does not show
The study was conducted in a laboratory setting, which may influence arousal levels, particularly in children with anxiety, and findings may not generalize to naturalistic environments like schools or homes. Not all children completed all tasks; several dropped out before the active task, potentially biasing results toward those who could tolerate the demands. The sample excluded children on non-stimulant medication and those with intellectual disability or severe sensory difficulties who were deemed unsuitable for the study, limiting generalizability to more complex clinical profiles. Stimulant medication for ADHD was withdrawn for 24 hours, so results reflect off-medication states, which may differ from the physiological profile of a child treated in daily life.
Declared interests
Funded by the Waterloo Foundation, Baily Thomas Charitable Fund, NIHR Nottingham Biomedical Research Centre, and the University of Nottingham. No specific conflicts of interest declared by authors.
The easy way to misread this
Do not assume that a child's diagnosis reliably predicts their physiological arousal state. The study showed significant heterogeneity within the autism group, with some children displaying hypo-arousal profiles similar to those with ADHD. Treating arousal regulation based solely on a diagnostic label of autism or ADHD may miss the individual's actual physiological needs.