CHICAGO (AP) — Children and teens in the U.S. suffer nearly 2 million concussions for sports and other play each year, with a new study finding many get no treatment.

The estimate, published in the journal Pediatrics on Monday, is based on 2013 data from emergency-room visits, hospitalizations, doctor-office visits, concussion reports made to high school athletic trainers, and information from previous concussion studies.

The study was led by pediatrician Dr. Mersine Bryan of Seattle Children's Hospital and involved kids age 18 and younger. Researchers say their figures are imprecise but they estimate half a million or more kids sought treatment from an athletic trainer or got no treatment at all.

The federal Centers for Disease Control and Prevention plans to create a system to track concussion rates and trends in children and adults.

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