Do symptoms of bipolar disorder commonly show during childhood?

Yes, but different: Children don't usually get the same cycle symptoms that adults get. For instance, manic episodes in childhood are not always the sleepless, risk taking, grandiose life of the adult person in a manic phase. They are usually irritable and aggressive instead. Also, moods can cycle very rapidly from one end to another, even within minutes. To complicate things further, adolescents are all of the above.