A new study of concussions suffered by high school athletes shows that loss of consciousness is uncommon, suggesting a greater understanding in the athletic community that loss of consciousness is not required for a concussion diagnosis.

The study, reported in the December 2010 issue of the American Journal of Sports Medicine, found that loss of conciousness or LOC was uncommon, occurring in less than 5% of concussions, a rate less than half the 10-11% rate reported in previous studies of high school athletes.

One possible explanation for the difference, said researchers at Children's Hospital, Boston, and Nationwide Children's Hospital in Columbus, Ohio,  was a "change over time in the understanding of sport-related concussion."  They noted that, as recently as 2007, more than four out of ten (42%) youth coaches surveyed believed a concussion only occurred when an athlete loses consciousness, but that in 2009, in a study of parents of young rugby players, 95% reported knowing that a player did not need to be "knocked out" to have suffered a concussion.

Their conclusion: "The percentage of diagnosed concussions associated with a loss of consciousness is likely decreasing, as the athletic community learns that loss of consciousness is not necessary for concussion diagnosis."