An alarming new statistic: Kids only report one out of every 10 concussions.
And with about 1.5 million junior high school and high school students playing football in the United States each year, that's a lot of unreported head injuries.
Chris Nowinski, a former professional wrestler, suffered multiple sports concussions through the years — along with long-term symptoms that can come with them. The dizziness, the headaches, the loss of memory — even depression.
"I had to retire from wrestling, sat in a dark room for 18 months just trying to get my head straight," Nowinski said.
Nowinski, who has dedicated his life to studying the effects of concussions on athletes, knew he had to get inside wrestler Chris Benoit's mind. So with the help of neurosurgeon Julian Bailes, he studied his brain.
What they found astounded everyone. At the time of the wrestler's suicide, Benoit's brain was so severely damaged it resembled the brain of an 85-year-old Alzheimer's patient.
"He had the same sort of brain injury, dead brain cells and their connections. And that's what you get a lot of times in demented people who lose their capacity, their judgment," Bailes said.
Symptoms, Bailes says, that may be the result of a lifetime of concussions and could have in some way triggered Benoit's dark decisions in the end. In late June, the professional wrestler killed his wife, 7-year-old son and himself.
"I don't think any of us, prior to very recently, have realized that concussions can affect your brain in such a drastic way, at such a young age," Nowinski said.
Benoit likely had no idea of the extent of his brain damage.
Experts say his ignorance is characteristic of many young athletes, children and teens, coming up behind him.
Like 15-year-old Willie Baun, whose parents won't forget one play on the field.
His father, Whitey Baun, said, "It was absolutely a normal hit, nothing that made me go, 'Oh! That was a real hit!'"
But it was a real hit, for Willie's brain. In fact, doctors learned it was his second concussion in just six weeks. And there were real consequences — it's called post-concussion syndrome.
Willie Baun lost his memory.
"He looked at his homework and he had not a clue as to what to do, how to tackle it, he was almost in tears saying I don't understand any of this," his mother, Becky Baun, said.
With help from doctors, eight months later, Willie's memory was back. But if it had gone unnoticed, it could have led to much bigger problems.
"There is still this mentality that if you get your bell rung or you get dinged, as they understand it, they try to play through it because they think they are being tough. In reality that's a concussion," said Dr. Matt Lively of West Virginia University.
Experts say parents should watch more than just the game:
After a rough play, ask your child whether he or she is dizzy or lightheaded.
Does he or she have recurrent headaches?
Bailes says the rule of thumb is three concussions and it's time to stop playing the sport.
High schools around the country are becoming more aware of the possible dangers and long-term effects of concussions. Parents and coaches are also now using the HeadMinder test.
After a hit, the player answers a series of questions to test current cognitive ability. The score is tested against a baseline number to see whether there's been an injury and whether the player is ready to go back on the field.