Concussion rates in US high-school athletes more than doubled between 2005 and 2012, according to a new national study using data on nine team sports. Researchers suspect the upward trend in reported concussions reflects increased awareness. Overall, the rate increased from .23 to .51 concussions per 1,000 athlete exposures. An athlete exposure is defined as one athlete participating in one competition or practice.

Source: Concussion rate in high-school athletes more than doubled in 7-year period, U.S. study finds