The onset of Major Depressive Disorder typically occurs during a person’s teens or 20s, but can occur before puberty. Although gender differences are not seen during childhood, depression is diagnosed twice as often in girls as in boys by adolescence. This divergence becomes evident at age 14.
By the age of 18, 20 to 25 percent of adolescents have experienced an episode of a mood disorder, and 10 to 15 percent of children have reported moderate to severe depressive symptoms prior to starting puberty, with one to nine percent diagnosable as depression.
By age 20, a child with a parent with a mood disorder has a 40 percent chance of experiencing a depressive episode. This rate increases to 60 percent by age 25.
Several studies indicate that a genetic connection may exist between parental depression and mental illness in children. However, it is well believed that environmental factors also play a critical role in the development of the disorder. Read more about whether children of depressed parents are at increased risk to develop psychological disorders.
— Dr. Patricia Turner, Registered Psychologist, Calgary, Alberta