title: Familial clustering of symptoms and disruptive behaviors in multiplex families with attention-deficit/hyperactivity disorder.
abstract: OBJECTIVE
  To examine familial clustering of attention-deficit/hyperactivity disorder (ADHD), ADHD subtypes, symptoms, and oppositional behaviors in affected sibling pairs (ASPs) and their parents.
  
  
  METHODS
  One hundred thirty-two ASPs, ranging in age from 5 to 25 years and ascertained through clinic and volunteer referrals, were examined for DSM-IV ADHD subtypes, oppositional defiant disorder (ODD), and conduct disorder (CD) with the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime version (K-SADS-PL). Two hundred fifty-six parents in these families were assessed by means of the SADS-Lifetime version, Modified for the Study of Anxiety Disorders, Updated for DSM-IV (SADS-LA-IV), and the Behavioral Disorders supplement of the K-SADS-PL to determine ADHD, ODD, and CD.
  
  
  RESULTS
  Fifty-five percent of families ascertained through an ASP have at least one parent with a lifetime diagnosis of ADHD. The frequency of ADHD in at least one parent was higher in families with at least one affected girl (63%) than in families with only affected boys (45%) (p = .02). There was no evidence that affected siblings or parents within ASP families showed similar patterns of ADHD symptoms, such as ADHD subtype classification. In contrast, CD significantly clustered in ASP families.
  
  
  CONCLUSIONS
  The sex difference in prevalence of ADHD among ASPs is consistent with a model of inheritance in which girls require a greater loading of familial influences to develop ADHD. The lack of familial clustering of ADHD symptoms within ASP families suggests that hyperactive and inattentive symptoms reflect common familial underpinnings and not unique familial effects. In contrast, CD seems to reflect unique familial underpinnings distinct from those underlying ADHD.
authors.affiliation: Department of Psychiatry, UCLA School of Medicine 90024-1759, USA. ssmalley@mednet.ucla.edu
authors.forename: S L
authors.initials: SL
authors.lastname: Smalley
authors.forename: J J
authors.initials: JJ
authors.lastname: McGough
authors.forename: M
authors.initials: M
authors.lastname: Del'Homme
authors.forename: J
authors.initials: J
authors.lastname: NewDelman
authors.forename: E
authors.initials: E
authors.lastname: Gordon
authors.forename: T
authors.initials: T
authors.lastname: Kim
authors.forename: A
authors.initials: A
authors.lastname: Liu
authors.forename: J T
authors.initials: JT
authors.lastname: McCracken
mesh_terms: D000293:Adolescent; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology* / Q000235:genetics* / Q000523:psychology; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D015897:Comorbidity; D019955:Conduct Disorder / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D005163:Factor Analysis, Statistical; D005260:Female; D020022:Genetic Predisposition to Disease / Q000523:psychology*; D006801:Humans; D015141:Los Angeles / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009679:Nuclear Family; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D012494:Sampling Studies; D012737:Sex Factors