Assessment of autonomic nervous system activity in adults with attention deficit hyperactivity disorder during cognitive task performance.

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Background: Diagnosing adult ADHD is challenging due to its clinical diversity, variable symptom expression, and subjective severity evaluations. Consequently, there is an increasing interest in identifying predictive biomarkers to aid in diagnosis, prognosis, and treatment response assessment. Aim: To assess the effectiveness of measuring autonomic nervous system (ANS) activity and skeletal muscle tension during cognitive tasks in differentiating adults with Attention-Deficit/Hyperactivity Disorder (ADHD) from healthy individuals. Subjects and methods: In this case–control study, 50 adults (aged 18–45) diagnosed with ADHD and 50 matched controls underwent diagnostic assessments using SCID-I, SCID-II, ASRS, and CAARS. Heart rate variability (RMSSD), electrodermal activity (EDA), and surface electromyography (sEMG) were recorded at rest and during the Sustained Attention to Response Task (SART). Results: At baseline, ADHD participants showed higher sEMG (U = 401.00, p < .001), lower RMSSD (U = 738.00, p < .001), and lower EDA (U = 963.00, p = .048). During SART, ADHD participants made more GO errors (U = 579.00, p < .001) and NO-GO errors (U = 336.00, p < .001). Repeated-measures ANOVA revealed significant time × group interactions for sEMG (F(1,98) = 11.51, p = .001, η²ₚ = .105), RMSSD (F(1,98) = 96.54, p < .001, η²ₚ = .496), and EDA (F(1,98) = 24.81, p < .001, η²ₚ = .202). Conclusion: Adult ADHD is associated with autonomic hypoarousal and reduced physiological responsiveness during sustained attention tasks, accompanied by increased muscle activation, possibly as a compensatory mechanism. Multimodal ANS profiling could improve ADHD diagnostic accuracy.