Bipolar disorder in children, or pediatric bipolar disorder (PBD), is a mental disorder in children and adolescents that, like bipolar disorder (BD) in adults, is characterized by extreme changes in mood and behavior accompanying periods of depressed or irritable moods and periods of elevated moods called manic or hypomanic episodes. These shifts are sometimes quick, but usually are gradual. The average age of onset of pediatric bipolar disorder is unclear, but the risk increases with the onset of puberty. Pediatric bipolar disorder is typically more severe and has a poorer prognosis than bipolar disorder with onset in late-adolescence or adulthood.