Bipolar Disorder in pediatric patients: A nationwide retrospective study from 2000 to 2015

•Pediatric bipolar disorder hospitalization rates increased 4.16 times in Portugal from 2000 to 2015.•This increase in annual rates was non-linear throughout the study period.•Similar to other European studies, a lower prevalence of pediatric bipolar disorder was found when compared to United States studies.•Hospitalized patients were mainly female, with a median age of 16 years, and most admissions were emergent.•These results suggest the need for a low threshold for early interventions in the community in order to avoid emergent admissions and re-hospitalizations. Pediatric Bipolar Disorder (BD) has been the focus of increased attention. To date, in Portugal, there is no evidence available for pediatricBD-related hospitalization rates. This study aimed to describe and characterize all pediatric hospitalizations with a primary diagnosis of BD registered in Portugal from 2000 to 2015. A retrospective observational study was conducted. Pediatric (