One in 12 teenagers in the U.S. has suffered from depression, according to survey results released by a federal health agency that are similar to past findings.

Teenage girls were more than twice as likely as boys to report they'd had an episode of depression lasting at least two weeks. During that time, they were often in a sad mood, took less pleasure from life and had other symptoms such as difficulty sleeping, reduced energy or a diminished ability to concentrate, according to the report by the Substance Abuse and Mental Health Services Administration. Among females, 12.7 percent reported having depression, compared with 4.6 percent of boys.

Half of the 2.1 million teens noted in the survey as depressed said their condition had seriously interfered with their ability to cope and operate normally in their daily lives. Parents of troubled teens were urged to speak with mental health professionals.

"Parents concerned about their child's mental health should seek help with the same urgency as with any other medical condition," said Terry Cline, the agency's administrator, in a statement posted on its Web site. "Appropriate mental health care can help their child recover and thrive."

The report is based on the results of surveys taken from 2004 to 2006 of almost 68,000 12- to- 17-year-olds throughout the U.S. Survey-takers randomly visited households to gather the information.

Previous studies have reported that up to 2.5 percent of children and up to 8.3 percent of adolescents in the U.S. suffer from depression, according to a fact sheet produced by the National Institute of Mental Health, a U.S. agency.