title: Noradrenergic mechanisms in ADHD children with and without reading disabilities: a replication and extension.
abstract: OBJECTIVE
  To examine noradrenergic (NA) function in children with attention-deficit hyperactivity disorder (ADHD) by replicating and expanding upon a previous finding that ADHD children with and without reading disabilities (RD) differ in plasma levels of the NA metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG).
  
  
  METHODS
  Plasma levels of MHPG were compared in ADHD children who were subdivided on the basis of the presence or absence of RD. Subsequently, this replication sample was combined with a previously studied sample to further explore the relationship between plasma MHPG levels and measures of cognitive function in children with ADHD.
  
  
  RESULTS
  Plasma levels of MHPG were significantly lower in ADHD children without RD, compared with those with RD, replicating a published finding. Analyses in the combined sample indicated that, among children with ADHD, plasma MHPG levels were inversely associated with measures of academic achievement and verbal processing, but not parent or teacher ratings of behavior or continuous performance test measures of attention and impulsivity.
  
  
  CONCLUSIONS
  These data indicate that children with ADHD are not homogeneous with regard to NA function and that neurochemical variation is closely associated with differences in clinical characteristics of the children.
authors.affiliation: Psychology Department, Queens College, City University of New York, Flushing 11367, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Halperin
authors.forename: J H
authors.initials: JH
authors.lastname: Newcorn
authors.forename: V H
authors.initials: VH
authors.lastname: Koda
authors.forename: L
authors.initials: L
authors.lastname: Pick
authors.forename: K E
authors.initials: KE
authors.lastname: McKay
authors.forename: P
authors.initials: P
authors.lastname: Knott
mesh_terms: D000124:Achievement; D001288:Attention / Q000502:physiology; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002648:Child; D004410:Dyslexia / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000097:blood; D009434:Neural Pathways / Q000503:physiopathology; D009638:Norepinephrine / Q000502:physiology*; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology
chemical_list: D018341:Receptors, Adrenergic, alpha-2; D008734:Methoxyhydroxyphenylglycol; D009638:Norepinephrine