WASHINGTON (AP) -- Researchers are offering a computerized screening tool to high schools for free in hopes of identifying teenagers who are suffering from depression.

Columbia University's "TeenScreen" survey asks teenagers questions designed to find those at risk for suicide or those with other mental health problems. It is now being used at 66 sites, including schools, community centers and homeless shelters, in 27 states.

On Thursday, the school began an initiative that promises to give the computer program to 400 more communities.

"In an hour or less, it is now possible to find young people with serious mental health problems, many who are suffering silently and don't know that what they are experiencing isn't normal," said Dr. David Shaffer, chief of adolescent psychiatry at Columbia, who led the research effort to develop the screening program.

The questionnaire is meant to identify teenagers who need a more detailed assessment. Studies have found that the questionnaire accurately identifies most teenagers who were judged suicidal through a full psychiatric diagnosis. It also flagged many were not suicidal, though many of them were depressed.

Columbia estimates that more than 800,000 U.S. teenagers suffer from depression each year, with more than 500,000 attempting suicide.

The screening program asks a variety of questions about mental well-being. Examples include: "In the last year, has there been a time when nothing was fun for you and you just weren't interested in anything?" and "Has there been a time when you couldn't think as clearly or as fast as usual?"

The questionnaire also asks about suicide attempts, alcohol and drug use.

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