Jul 24, - Some symptoms that suggest a teenager might have bipolar disorder are: Uncharacteristic periods of anger and aggression. Grandiosity and overconfidence. Easy tearfulness, frequent sadness. Needing little sleep to feel rested. Uncharacteristic impulsive behavior. Moodiness. Confusion and inattention. Feb 14, - Identifying the symptoms of bipolar disorder (manic depression) can be and other behaviors.1 The average age of symptom onset is roughly.