I think the term also used is- early onset depression, which refers to depression in young people and adolescents, tzw depresja dziecięca/ (i)młodzieńcza.
Depresja u dzieci i młodzieży....ale trzeba zobaczyć cały tekst, czy o to chodzi, skoro tutaj brak kontekstu.

....Early Depression, Late Consequences
Recent studies have shown that, by age 15, about 6% to 7% of adolescents experience depression (which is 2 to 3 times more common in . . .
http://psychiatry.jwatch.org/cgi/content/citation/2002/724/1...
http://www.emeraldinsight.com/Insight/viewContentItem.do?con...

http://www.nami.org/Content/ContentGroups/Helpline1/Facts_Ab...

http://www.cmppp.edu.pl/node/23393
http://www.google.co.uk/search?hl=en&q=" depresja dziecięca ...
http://209.85.229.132/search?q=cache:tkk_hvztOFIJ:bielsktroj...