*The following is excerpted from an online article posted on HealthDay.
As many as one in five U.S. teens may have suffered a concussion, and contact sports might often be the cause.
That's the conclusion of new research that included more than 13,000 teens. It also found that nearly 6 percent of teens reported having more than one concussion.
These findings show that the number of middle school and high school students who will suffer a concussion in their lifetime is greater than thought, said lead researcher Phil Veliz.
"The prevalence of concussions may be much higher than what is reported from emergency room data," said Veliz, a research assistant professor at the University of Michigan.
"Participation in contact sports shows a strong association with reporting a diagnosed concussion," he added.
These findings suggest a greater need for prevention efforts in schools and communities, "particularly with respect to interscholastic sports and youth sport organizations that operate outside the school environment," Veliz said.
For the study, Veliz and his colleagues collected data from more than 13,000 boys and girls in grades 8, 10 and 12, who took part in the 2016 Monitoring the Future survey.
The survey is done annually in schools across the country.
For the first time, last year's survey included the question: "Have you ever had a head injury that was diagnosed as a concussion?"
The researchers found that 19.5 percent of the teens said they had had at least one diagnosed concussion in their lifetime. Fourteen percent reported one diagnosed concussion, and 5.5 percent reported being diagnosed with a concussion more than once.
Factors that increased the odds of a concussion included being male, white, in a higher grade and participating in competitive sports, the findings showed.
Taking part in contact sports -- such as football -- significantly increased the risk of a concussion. About 11 percent of those participating in contact sports reported more than one concussion.