Tested at the beginning and end of one season, 22 percent of those students who participated in contact sports scored significantly lower in memory and learning skills than expected, as opposed to only 4 percent of non-contact sport athletes.

“These results were found shortly after the season and we do not know how long the effect [of the head impacts] lasts,” study researcher Thomas McAllister, of Dartmouth College, said in a statement. “While it may be bad for the 22 percent, the good news is that overall there were few differences in the test results between the athletes in contact sports and the athletes in non-contact sports,” he added.