Monozygotic twins discordant for attention-deficit/hyperactivity disorder: Ascertainment and clinical characteristics

Wendy S. Sharp, Rebecca F. Gottesman, Deanna K. Greenstein, Christen L. Ebens, Judith L. Rapoport, F. Xavier Castellanos

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Objective: Nongenetic factors and phenomenology of attention-deficit/ hyperactivity disorder (ADHD) were examined in monozygotic (MZ) twin pairs discordant for ADHD. Method: Recruitment included telephone screening (n = 297 pairs), behavioral ratings obtained from parents and teachers (n = 59 pairs), and, finally, in-person assessment (n = 25 pairs; structured classroom observation, diagnostic interview, psychoeducational evaluation, birth record review, establishment of monozygosity, and anatomic brain imaging). Affected twins were further contrasted with previously studied affected singletons. Results: Of the 25 MZ twin pairs qualifying for in-person evaluation, only 10 proved discordant for ADHD. Affected twins were mostly comparable with affected singletons on clinical measures, although fathers' self-ratings of childhood ADHD status were significantly lower in twins than in singletons. Conclusions: Discordance for ADHD in MZ twins appears to be ascribable to greater environmental discordance and decreased familiality. Despite these differences, affected twins were phenotypically comparable with affected singletons. Thus MZ twins discordant for ADHD, while rare, can inform research on the etiology and pathophysiology of this disorder.

Original languageEnglish (US)
Pages (from-to)93-97
Number of pages5
JournalJournal of the American Academy of Child and Adolescent Psychiatry
Issue number1
StatePublished - Jan 2003
Externally publishedYes


  • Attention-deficit/hyperactivity disorder
  • Discordant twins
  • Monozygotic twins
  • Subject ascertainment

ASJC Scopus subject areas

  • Developmental and Educational Psychology
  • Psychiatry and Mental health


Dive into the research topics of 'Monozygotic twins discordant for attention-deficit/hyperactivity disorder: Ascertainment and clinical characteristics'. Together they form a unique fingerprint.

Cite this