That is an interesting and powerful article. These quotes caught my attention.

"Clinical records, among the data serving as the foundation for this paper, confirmed that some highly gifted children--especially those in undifferentiated school programs with no access to like-minded peers and appropriate learning experiences--may exhibit signs of depressive disorder as early as age 7."

"Children often... do not wear it [depression] on their sleeves as adults do. Children tend to be depressed in an extremely quiet way. They often creep into their rooms or other secluded places and cry while appearing cheerful in public settings. Usually they don't look as sad, tearful, or as slowed down as depressed adults. By the time a child exhibits signs of depression for all to see, he or she is usually severely depressed."