Boys under report their depression and often don’t get help. Unfortunately this pattern continues into adulthood. Eight percent of all teenagers ages 12-17 report  feeling depressed two or more weeks in the last year and this number breaks down very differently for girls than boys.  
In older teens, 15-17, 15% of girls and 6.4% of boys say they had a major depressive period in the preceding year.
Early intervention is key because depressed teenagers abuse drugs and/or alcohol to self medicate. Author Melissa Healy discusses Teen Screen a standardized mental health screening test for adolescents in The Los Angeles Times.