Serious depression affects more than 2 million teens in the U.S.

A survey released in the U.S. has revealed that in the past year in excess of 2 million American teenagers experienced a serious bout of depression.

The survey conducted by the Substance Abuse and Mental Health Services Administration (SAMHSA) found 8.5 percent of adolescents aged 12 to 17 described having had a major depressive episode in the previous year.

There were apparently marked differences by gender with 12.7 percent of girls and 4.6 percent of boys affected by depression.

According to the federal government report, depression is the leading cause of suicide, and suicide in turn is the third-leading cause of death for 15- to 24-year-olds in the U.S.

The researchers say the data shows the rate of depression increases with increasing age.

The report was compiled by SAMHSA using data from a national survey on drug use with more than 67,700 youths aged 12 to 17 taking part.

Questions were asked about mood and depression and they were also asked to rate how depression affected them using the Sheehan Disability Scale, which measures impact on family, friends, chores at home, work and school.

A major depressive episode was defined as 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 or self-image.

Almost half of the teenagers who had suffered major depression said it severely impaired their ability to function and the worst cases were unable to carry out normal activities for an average of 58 days in the year.

Experts say fortunately, depression responds very well to early intervention and treatment and parents concerned about their child's mental health should seek help with the same urgency as with any other medical condition.