Geller, B., Zimmerman B., Williams M., BolhofnerK., Craney JL. Am J Psychiatry 2001 Jan;158 (1):125-7.

In a 10-year follow-up study of 72 children diagnosed with depression before puberty(average age at diagnosis was 10), nearly half (48%) developed Bipolar Disorder by the time they reached 20. Having a parent and a grandparent with mania (a syndrome of Bipolar I) predicted a Bipolar I outcome for a child with major depression. Children with ADHD or psychotic symptoms were excluded from the study; if included, the "switch rate" (from depression to mania) would be expected to be even higher.

(Abstract by Martha Hellander, The Balanced Mind Foundation Executive Director).