title: Is overactivity a core feature in ADHD? Familial and receiver operating characteristic curve analysis of mechanically assessed activity level.
abstract: OBJECTIVE
  Symptoms of overactivity form part of the DSM-IV criteria for the combined or hyperactive-impulsive subtypes of attention-deficit/hyperactivity disorder (ADHD); yet little data exist that would quantify the nature of the overactivity component. We aimed to quantify the ability of four different measures of motion sensor data, taken from actigraphs, and the intraindividual variability (IIV) in these measures, to distinguish ADHD cases from controls. Furthermore, we aimed to investigate the degree of shared familial influences on these measures and the ADHD diagnosis.
  
  
  METHODS
  Receiver operating characteristic analysis and multivariate structural equation modeling were used on actigraph data collected during a cognitive testing session in a sample of 116 ADHD combined-type probands, 119 of their siblings, and 218 control siblings (age range 6-18 years).
  
  
  RESULTS
  Three measures of actigraph data--the number of movements made, the magnitude of these movements, and the IIV in the magnitude of movement--yielded an area under the curve of up to 0.8, indicating an ability to distinguish between cases and controls. The latter two of these measures showed significant shared familial vulnerability with an ADHD diagnosis, with high ADHD-actigraph familial correlations.
  
  
  CONCLUSIONS
  The actigraph data support the DSM-IV conceptualization of including overactivity as one of the core features within ADHD combined subtype. The magnitude of movements made, and the IIV of these movements, may be suitable candidates for future molecular genetic studies seeking to identify polymorphisms associated with the risk for ADHD. Further research should investigate if these findings generalize to a more naturalistic, homelike setting.
authors.affiliation: Drs. Asherson, Rijsdijk, Kunsti and Ms. Wood are with King's College London. Electronic address: alexis.wood@iop.kcl.ac.uk.
authors.forename: Alexis C
authors.initials: AC
authors.lastname: Wood
authors.affiliation: Drs. Asherson, Rijsdijk, Kunsti and Ms. Wood are with King's College London.
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.affiliation: Drs. Asherson, Rijsdijk, Kunsti and Ms. Wood are with King's College London.
authors.forename: Frühling
authors.initials: F
authors.lastname: Rijsdijk
authors.affiliation: Drs. Asherson, Rijsdijk, Kunsti and Ms. Wood are with King's College London.
authors.forename: Jonna
authors.initials: J
authors.lastname: Kuntsi
mesh_terms: D056044:Actigraphy; D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis* / Q000235:genetics* / Q000523:psychology; D002648:Child; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D007206:Individuality; D008297:Male; D008960:Models, Psychological; D009043:Motor Activity; D015999:Multivariate Analysis; D010552:Personality Assessment; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D012372:ROC Curve; D012016:Reference Values; D012931:Social Environment