Etiology of mood disorders in children and adolescents

What evidence is there supporting the etiology of mood disorders among children and adolescents? Select one or two factors and please describe.

Textbook: Kaplan and Sadock’s Concise Textbook of Child and Adolescent Psychiatry
Author(s): Benjamin J. Sadock MD, Virginia Alcott Sadock MD -ISBN/ISSN -9780781793872