Incidence, characteristics and course of narrow phenotype paediatric bipolar I disorder in the British Isles.

OBJECTIVE: To estimate the surveillance incidence of first-time diagnosis of narrow phenotype bipolar I disorder (NPBDI) in young people under 16 years by consultants in child and adolescent psychiatry (CCAP) in the British Isles and describe symptoms, comorbidity, associated factors, management strategies and clinical outcomes at 1-year follow-up. METHOD: Active prospective surveillance epidemiology was utilised to ask 730 CCAP to report cases of NPBDI using the child and adolescent psychiatry surveillance system. RESULTS: Of the 151 cases of NPBDI reported, 33 (age range 10-15.11 years) met the DSM-IV analytical case definition with 60% having had previously undiagnosed mood episodes. The minimum 12-month incidence of NPBDI in the British Isles was 0.59/100 000 (95% CI 0.41-0.84). Irritability was reported in 72% cases and comorbid conditions in 51.5% cases with 48.5% cases requiring admission to hospital. Relapses occurred in 56.67% cases during the 1-year follow-up. CONCLUSIONS: These rates suggest that the first-time diagnosis of NPBDI in young people <16 years of age by CCAP in the British Isles is infrequent; however, the rates of relapse and admission to hospital warrant close monitoring.