Age differences in the phenomenology of pediatric bipolar disorder

Background: The primary purpose of this study was to explore whether age differences in the phenomenology of bipolar disorders from 4 to 17 years of age exist. Methods: Outcome measures included questionnaires pertaining to mood symptoms, psychosocial functioning, and family history of psychiatric illness. Phenomenology was examined in two diagnostic groups: syndromal bipolar disorder (bipolar I or II) and subsyndromal bipolar disorder (bipolar disorder not otherwise specified or cyclothymia) and across six age cohorts: 4-6, 7-8, 9-10, 11-13, and 14-17 years. Analyses examined linear and non-linear age effects on clinician-rated measures of mood and psychosocial functioning. Results: Participants were 535 outpatients (339 males) ages 4-17 years. The proportion diagnosed with comorbid ADHD was significantly lower in the oldest age group. Age groups showed significant moderate decreases in motor activity, aggression, and irritability with age. Many symptoms of depression showed significant increases with age. BP I cases showed much higher manic symptoms, and BP I and BP II cases indicated slightly to moderately higher depressive symptoms, compared to subsyndromal cases. These patterns held after adjusting for comorbid ADHD, and age did not interact with syndrome status. There were also age differences in total scores for measures of mood symptoms and psychosocial functioning. Limitations: Mood ratings were completed based on the same interview that informed the research diagnoses. Also, mood episode at time of interview was not captured. Conclusions: These findings affirm the existence of bipolar disorder from pre-school children through adolescence, with a similar clinical presentation across a wide developmental age span.