When you think about health threats common to American teenagers, what comes to mind?

Perhaps sexually transmitted diseases, obesity or sports injuries. Here’s one major issue you may not have considered: mental health.

This health threat is a big one. According to a report from the National Research Council and Institute of Medicine, up to one in five U.S. children, including teens, struggle with a mental health problem each year. And a new study from Duke University shows that many don’t get the care they need.

The scientists analyzed statistics from across the country on psychiatric disorders in teens. They found that more than half of teenagers with mental health problems do not receive treatment for them. Those who do are not likely to get specialized care.

Most teens who did receive care got it in school. The next largest group — 23 percent —was treated at a facility specializing in mental health. Others found help from a primary care doctor, the juvenile justice system, a human services organization or alternative health care providers. It’s great these groups offer support, but mental health problems are serious diseases best treated by specialists. However, as the study authors state, pediatric mental health professionals are in short supply.

But it’s not impossible to get care. Government health centers, teaching hospitals and college health services may employ specialists, and they sometimes offer low-cost mental health care.

Parents, if your teen has a mental health problem, even one that seems small, don’t ignore it. Fight to get specialized care for your child, and emphasize to him that you support him. Untreated mental health disorders can have long-lasting negative effects, so timely treatment is key.