One in every 12 American teens (about 2.1 million) ages 12 to 17 experienced major depression in the past year, according to a report released Tuesday by the Substance Abuse and Mental Health Services Administration.

There was a large gender difference, with 12.7 percent of females and 4.6 percent of males reporting major depression. It's defined as a period of two weeks or longer of depressed mood or loss of interest or pleasure, and at least four other symptoms -- such as problems with sleep, energy, concentration and self-image -- reflecting a change in functioning.