What is actually observed in so-called 'bipolar children'? If you read the research reports carefully, they describe broad and persistent emotional dysregulation. Although these children have mood swings, they do not develop manic or hypomanic episodes. They are moody, irritable, oppositional and likely to misbehave—like all children with disruptive behavior disorders. Their grandiose thinking usually consists of little beyond boastfulness. No evidence from genetics, neurobiology, follow-up studies or treatment response shows that this syndrome has anything in common with classical bipolarity.

The Intelligent Clinician's Guide to the DSM-5