Hospital-treated bipolar disorder in adolescence in Finland 1980-2010: Rehospitalizations, diagnostic stability, and mortality.

Aims: Estimates of the occurrence of bipolar disorder among adolescents vary from country to country and from time to time. Long delays from first symptoms to diagnosis of bipolar disorder have been suggested. Studies among adults suggest increased mortality, particularly due to suicide and cardiovascular diseases. We set out to study the prognosis of adolescent onset bipolar disorder in terms of rehospitalizations, diagnostic stability, and mortality.

Methods: The study comprised a register-based follow-up of all adolescents admitted to psychiatric inpatient care for the first time in their lives at age 13-17 during the period 1980-2010. They were followed up in the National Care Register for Health Care and Causes of death registers until 31 December 2014.

Results: Incidence of bipolar disorder among 13- to 17-year-old adolescents over the whole study period was 2.8 per 100, 000 same aged adolescents, and across decades, the incidence increased six-fold. Patients with bipolar disorder during their first-ever inpatient treatment were rehospitalized more often than those treated for other reasons. Conversion from bipolar disorder to other diagnoses was far more common than the opposite. Mortality did not differ between those firstdiagnosed with bipolar disorder and those treated for other reasons.

Conclusion: The incidence of adolescent onset bipolar disorder has increased across decades. The present study does not call for attention to delayed diagnosis of bipolar disorder. Adolescent onset bipolar disorders are severe disorders that often require rehospitalization, but diagnostic stability is modest. Mortality is comparable to that in other equally serious disorders.