title: Statistical Evidence Suggests that Inattention Drives Hyperactivity/Impulsivity in Attention Deficit-Hyperactivity Disorder.
abstract: BACKGROUND
  Numerous factor analytic studies consistently support a distinction between two symptom domains of attention-deficit/hyperactivity disorder (ADHD), inattention and hyperactivity/impulsivity. Both dimensions show high internal consistency and moderate to strong correlations with each other. However, it is not clear what drives this strong correlation. The aim of this paper is to address this issue.
  
  
  METHODS
  We applied a sophisticated approach for causal discovery on three independent data sets of scores of the two ADHD dimensions in NeuroIMAGE (total N = 675), ADHD-200 (N = 245), and IMpACT (N = 164), assessed by different raters and instruments, and further used information on gender or a genetic risk haplotype.
  
  
  RESULTS
  In all data sets we found strong statistical evidence for the same pattern: the clear dependence between hyperactivity/impulsivity symptom level and an established genetic factor (either gender or risk haplotype) vanishes when one conditions upon inattention symptom level. Under reasonable assumptions, e.g., that phenotypes do not cause genotypes, a causal model that is consistent with this pattern contains a causal path from inattention to hyperactivity/impulsivity.
  
  
  CONCLUSIONS
  The robust dependency cancellation observed in three different data sets suggests that inattention is a driving factor for hyperactivity/impulsivity. This causal hypothesis can be further validated in intervention studies. Our model suggests that interventions that affect inattention will also have an effect on the level of hyperactivity/impulsivity. On the other hand, interventions that affect hyperactivity/impulsivity would not change the level of inattention. This causal model may explain earlier findings on heritable factors causing ADHD reported in the study of twins with learning difficulties.
authors: Institute for Computing and Information Sciences, Radboud University, Nijmegen, The Netherlands.
authors: Elena
authors: E
authors: Sokolova
authors: Institute for Computing and Information Sciences, Radboud University, Nijmegen, The Netherlands.
authors: Perry
authors: P
authors: Groot
authors: Institute for Computing and Information Sciences, Radboud University, Nijmegen, The Netherlands.
authors: Tom
authors: T
authors: Claassen
authors: Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.
authors: Kimm J
authors: KJ
authors: van Hulzen
authors: Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.
authors: Jeffrey C
authors: JC
authors: Glennon
authors: Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.|Department of Psychiatry, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.
authors: Barbara
authors: B
authors: Franke
authors: Institute for Computing and Information Sciences, Radboud University, Nijmegen, The Netherlands.
authors: Tom
authors: T
authors: Heskes
authors: Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.|Karakter Child and Adolescent Psychiatry University Centre, Nijmegen, The Netherlands.
authors: Jan
authors: J
authors: Buitelaar
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000523:psychology*; D002648:Child; D005260:Female; D006801:Humans; D007175:Impulsive Behavior; D008297:Male