Youth with a prior concussion take longer to recover from another Youth with a prior concussion take longer to recover from another. Sean Morey, former NFL wide receiver and current Executive Board Member NFL Players Association, testifies during a House Education and Labor Committee hearing on the Protecting Students Athletes from Concussions Act, in Washington on September 23, 2010. BOSTON, June 11 (UPI) -- Children without a prior concussion took 12 days on average to recover, but those with several previous concussions took longer, U.S. researchers say. Study author Matthew Eisenberg, a physician at Boston Children's Hospital, and colleagues said children and young adults ages 11-22 who came to a hospital emergency room with a repeat concussion -- either within a year, or multiple times over a lifetime -- took longer to recover than those with a first concussion, USA Today reported. A single previous concussion that occurred more than a year earlier did not increase the risk for a longer recovery, Eisenberg said. The study, published in the journal Pediatrics, found about 60 percent of the injured youth were hurt playing sports, and recovery from a second concussion within a year took an average of 35 days but some took months. Physicians are trying to understand what makes the difference among these recoveries and if those who have concussions when they are young are impacted when they are older, Eisenberg said.