Unfortunately, we know little about bipolar disorder in children as not only is it rare but it has only recently been recognized. What is currently thought is that between 0.2-0.3 percent of children have bipolar disorder type 1 and it’s present in about 1 percent of adolescents (this is the same number as in the adult population). However, recent estimates are that between 20-30 percent of adults with bipolar type 1 began showing symptoms under the age of 20. Those with childhood bipolar disorder also tend to have much more pronounced family histories of mental illness and thus are at greater genetic risk for the illness than people who experience bipolar disorder later in life.