title: Co-occurrence of bipolar and attention-deficit hyperactivity disorders in children.
abstract: OBJECTIVE
  Pediatric bipolar disorder (BPD) and attention-deficit hyperactivity disorder (ADHD) co-occur more frequently than expected by chance. In this review, we examine 4 potential explanations for the high rate of this common co-occurrence: (i) BPD symptom expression leads to overdiagnosis of ADHD in BPD youth; (ii) ADHD is a prodromal or early manifestation of pediatric-onset BPD; (iii) ADHD and associated factors (e.g., psychostimulants) lead to the onset of pediatric BPD; and (iv) ADHD and BPD share an underlying biological etiology (i.e., a common familial or genetic risk or underlying neurophysiology).
  
  
  METHODS
  Peer-reviewed publications of studies of children and adolescents with comorbid BPD and ADHD were reviewed.
  
  
  RESULTS
  There is a bidirectional overlap between BPD and ADHD in youth, with high rates of ADHD present in children with BPD (up to 85%), and elevated rates of BPD in children with ADHD (up to 22%). Phenomenologic, genetic, family, neuroimaging, and treatment studies revealed that BPD and ADHD have both common and distinct characteristics. While there are data to support all 4 explanations postulated in this paper, the literature most strongly suggests that ADHD symptoms represent a prodromal or early manifestation of pediatric-onset BPD in certain at-risk individuals. Bipolar disorder with comorbid ADHD may thus represent a developmentally specific phenotype of early-onset BPD.
  
  
  CONCLUSIONS
  The etiology of comorbid BPD and ADHD is likely multifactorial. Additional longitudinal and biological studies are warranted to clarify the relationships between BPD and ADHD since they may have important diagnostic and treatment implications.
authors.affiliation: Division of Bipolar Disorders Research, Department of Psychiatry, University of Cincinnati College of Medicine, 231 Bethesda Avenue, Cincinnati, OH 45267, USA.
authors.forename: Manpreet K
authors.initials: MK
authors.lastname: Singh
authors.forename: Melissa P
authors.initials: MP
authors.lastname: DelBello
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kowatch
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Strakowski
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology*; D001714:Bipolar Disorder / Q000453:epidemiology*; D002648:Child; D015897:Comorbidity; D006801:Humans