Developmental differences according to age at onset in juvenile bipolar disorder.

Background: This study on a large sample of unselected, consecutive children and adolescents referred to a third-level hospital who received a diagnosis of bipolar disorder (BD) was aimed at exploring whether childhood-onset BD, as compared with adolescent-onset BD, presents specific clinical features in terms of severity, functional impairment, course, prevalent mood, pattern of co-morbidity, and treatment outcome.
Methods: A total of 136 patients, 81 males (59.6%) and 55 females (40.4%), mean age 13.5 +/- 2.9 years, meeting the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) diagnosis of BD according to a structured clinical interview Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (KSADS-PL), were included in the study.
Results: Eighty patients (58.8%) had a childhood-onset BD (before 12 years of age) and 56 (41.2%) had an adolescents-onset BD. Compared with the adolescent-onset BD, patients with childhood-onset were more frequently males and had a more frequent co-morbidity with attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD). An episodic course was found in only 42.5% of bipolar children, but 76.8% of youngsters with adolescent-onset BD. Severity, 6-month treatment outcome, prevalent mood (elated versus irritable), and co-morbid anxiety did not differentiate the two groups.
Conclusions: Our findings suggest that a very early age at onset may identify a form of BD with a more frequent subcontinuous course and a heavy co-morbidity with ADHD.