These studies could teach us more about why and how concussions tend to occur, as well as
how subconcussive blows — a hit to the head that doesn't result in a concussion — affect an athlete over a long period of time.
But not all of these persons had a history of concussion and this suggests that undiagnosed
subconcussive blows may also contribute to CTE, they explain, and call for more research into
how the condition develops and to determine other risk factors.