It might be tempting to roll your eyes when your teenager screams at you or slams a door. But where does stereotypical teenage behavior end and mental illness begin? An influential panel of doctors says the line may be blurrier than originally believed. Now they are urging practitioners to routinely screen all American teenagers for depression, a bold departure from previous recommendations.

According to the U-S Preventive Services Task Force, which sets guidelines for doctors on a variety of issues, nearly two-million American teens are depressed. Most are undiagnosed and untreated. Even more troubling: Half of all serious adult psychiatric illnesses start before age fourteen, but research suggests parents may be oblivious. One study found that parents were unaware of ninety percent of suicide attempts made by teenagers.

The task force recommends all children… even those without symptoms… be screened using simple but highly detailed questionnaires. This goes beyond the recommendation of the American Academy of Pediatrics, which advises pediatricians simply ask teenage patients about depression.

The questionnaires focus on depression tip-offs, such as mood, anxiety, appetite changes and substance abuse. The task force said treatment, including psychotherapy, can help children cope. Left untreated, depression can lead to persistent sadness, social isolation, school problems and even suicide. In fact, public health officials reported the first increase in teen suicides last year after a thirteen-year decline.

So the next time your teenager behaves like a drama queen, don’t just dismiss it. It could be the symptom of something much larger.