title: Should sluggish cognitive tempo symptoms be included in the diagnosis of attention-deficit/hyperactivity disorder?
abstract: OBJECTIVE
  To determine the impact of including sluggish cognitive tempo items on the factor and latent class structure of attention-deficit/hyperactivity disorder (ADHD) subtypes in boys and girls.
  
  
  METHODS
  Parent report of two sluggish cognitive tempo items on a population-based sample of 1430 female twins and 1414 male twins were analyzed along with parent report of the 18 DSM-IV ADHD items using principal components analysis and latent class analysis.
  
  
  RESULTS
  The inclusion of the two sluggish cognitive tempo items resulted in distinct factor structures for boys and girls. For boys there were separate inattentive, hyperactive/impulsive, and sluggish factors. For girls there were separate inattentive/sluggish, hyperactive, and impulsive factors. In contrast, sluggish cognitive tempo items had minimal impact on the latent class structure of ADHD for both boys and girls.
  
  
  CONCLUSIONS
  The inclusion of sluggish cognitive tempo items markedly changed ADHD symptom associations for boys and girls in a factor analytic framework. In contrast, latent class subtyping of ADHD shows limited impact of the inclusion of sluggish cognitive tempo items, emphasizing the very different assumptions about underlying continua of behavior rather than discrete classes that distinguish the two approaches.
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St Louis, MO 63110, USA. toddr@psychiatry.wustl.edu
authors.forename: Richard D
authors.initials: RD
authors.lastname: Todd
authors.forename: Erik R
authors.initials: ER
authors.lastname: Rasmussen
authors.forename: Catherine
authors.initials: C
authors.lastname: Wood
authors.forename: Florence
authors.initials: F
authors.lastname: Levy
authors.forename: David A
authors.initials: DA
authors.lastname: Hay
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000145:classification / Q000175:diagnosis*; D002648:Child; D003071:Cognition; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D011159:Population Surveillance; D013997:Time Factors