This is a relatively recent diagnostic category, which is considered a more conservative approach than the free-for-all giving small children bipolar affective disorder diagnoses that was fashionable for a period, mostly during the early 2000s. The trajectory does include adult bipolar for some children, but interestingly, the more consistent finding is adult depression or anxiety disorders.
And I would agree with SFP that, as with all mental health diagnoses (with adults too, but especially with children), it's important to rule out other organic bases of the symptoms.
