Nearly one in 10 American teenagers, or 2.2 million, experienced major depression last year, according to government statistics released Thursday that also showed that depressed youths were more likely to smoke, drink alcohol or abuse drugs.
Fewer than half received treatment, the survey found.
Overall, 9 percent of teens were depressed, with older teens more at risk than their younger peers, said the Substance Abuse and Mental Health Services Administration, or SAMHSA.
About 12 percent of youth aged 16 or 17 faced severe depression in 2004, compared with about 5 percent of those 12 or 13 years old. Among those age 14 or 15, 9 percent experienced a major episode.
"These new data serve as a wake-up call to parents. Mental health is a critical part of the overall health and well-being of their children," said SAMHSA administrator Charles Curie.
Treatment for depression among teenagers has been a controversial issue since a Food and Drug Administration scientist concluded in early 2004 that anti-depressants posed a suicide risk in youth. Another university-sponsored study also showed a link.
Since then the FDA has required drug manufacturers to disclose the possible risk on labels for anti-depressants. Some experts, including doctors, worried the warning would lead to fewer youths receiving treatment.
Thursday's findings, part of the agency's annual National Survey on Drug Use and Health, also showed very depressed youth aged 12 to 17 were twice as likely to engage in substance abuse than those who were not depressed.
About 28 percent of depressed teens used alcohol, while nearly 23 percent smoked cigarettes and another roughly 21 percent used drugs.
Among those who did not report a major episode, about 17 percent drank alcohol, about 11 percent smoked, and about 10 percent used drugs.
The report surveyed 70,000 people in the United States aged 12 and older. Major depression was considered a period of at least two weeks that included a loss of interest, depressed mood and at least four other symptoms such as a change in sleeping, eating or concentration.