• attention deficit and disruptive behavior disorders;
  • bipolar disorder;
  • child behavior disorders;
  • comorbidity;
  • differential diagnosis

Objectives:  Significant debate exists on whether early onset bipolar disorder is mistakenly attributed to attention deficit hyperactivity disorder (ADHD) or conduct disorder (CD), or whether ADHD and CD are frequently misdiagnosed as mania. We review the literature on the extent to which these disorders can be reliably differentiated, and describe the diagnostic confusion that may be the result of features common to both classes of disorders.

Methods:  The review focuses on research studies that have examined whether overlapping symptoms of bipolar disorder, ADHD, and CD contribute to misdiagnosis of the two classes of disorders, the prevalence of early onset bipolar disorder with comorbid ADHD or CD, and theories regarding the origins of this comorbidity.

Results:  Reliable and accurate diagnoses can be made despite the symptom overlap of bipolar disorder with ADHD and CD. Children with bipolar disorder and ADHD may have a distinct familial subtype of bipolar disorder. Some findings suggest that manic symptoms may represent `noise' that indicates the general severity of psychopathology in a child or adolescent.

Conclusions:  Further prospective studies may confirm whether early onset bipolarity can be successfully differentiated from ADHD or CD, whether all three types of disorders can be recognized in comorbid cases, or whether comorbid cases represent a distinct subtype of bipolar disorder.