title: Autonomic correlates at rest and during evoked attention in children with attention-deficit/hyperactivity disorder and effects of methylphenidate.
abstract: OBJECTIVE
  The aim of this study was to assess autonomic nervous system functioning in children with attention-deficit/hyperactivity disorder (ADHD) and to examine the effects of methylphenidate and focussed attention.
  
  
  METHODS
  Children with ADHD (n = 19) were tested while they were stimulant free and during a period in which they were on stimulants. On both occasions, autonomic nervous system functioning was tested at baseline and during focussed attention. Autonomic nervous system functioning of control subjects was also tested at baseline and during focussed attention. Autonomic nervous system activity was determined by means of heart rate variability (HRV) and skin conductivity analyses. Attention was evoked by means of the BioGraph Infiniti biofeedback apparatus. HRV was determined by time domain, frequency domain and Poincaré analysis of RR interval data. Skin conductivity was determined by the BioGraph Infiniti biofeedback apparatus.
  
  
  RESULTS
  The main findings of this study were (a) that stimulant-free children with ADHD showed a sympathetic underarousal and parasympathetic overarousal of the sympathovagal balance relative to control subjects; (b) methylphenidate shifted the autonomic balance of children with ADHD towards normal levels; however, a normal autonomic balance was not reached, and (c) stimulant-free children with ADHD exhibited a shift in the sympathovagal balance towards the sympathetic nervous system from baseline to focussed attention; however, methylphenidate appeared to abolish this shift.
  
  
  CONCLUSIONS
  Stimulant-free children with ADHD have a parasympathetic dominance of the autonomic balance, relative to control subjects. Methylphenidate attempts to restore the normal autonomic balance in children with ADHD, but inhibits the normal autonomic nervous system response to a cognitive challenge.
  
  
  METHODS
  These results indicate that methylphenidate may have a suppressive effect on the normal stress response. Although this may be of benefit to those who interact with children who suffer from ADHD, the implications for the physiological and psychological well-being of the children themselves are debatable. Further research is needed.
  
  
  CONCLUSIONS
  Only 19 children with ADHD and 18 control subjects were tested. Further studies should include prior testing in order to exclude children with possible co-existing learning disabilities. Cognitive function and emotional responses of children with ADHD were not tested.
authors.affiliation: Department of Physiology, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Bianca Lee
authors.initials: BL
authors.lastname: Negrao
authors.forename: Priyesh
authors.initials: P
authors.lastname: Bipath
authors.forename: Deborah
authors.initials: D
authors.lastname: van der Westhuizen
authors.forename: Margaretha
authors.initials: M
authors.lastname: Viljoen
mesh_terms: D000293:Adolescent; D001288:Attention / Q000187:drug effects / Q000502:physiology*; D001289:Attention Deficit Disorder with Hyperactivity / Q000188:drug therapy / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000187:drug effects / Q000503:physiopathology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology* / Q000627:therapeutic use; D002648:Child; D005260:Female; D005712:Galvanic Skin Response / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology* / Q000627:therapeutic use; D012146:Rest
chemical_list: D000697:Central Nervous System Stimulants; D008774:Methylphenidate