New study finds CTE may also be caused by small, repetitive hits

LOS ANGELES (KABC) -- A game-changing study that shows smaller repetitive hits to the head, not just concussions, may cause CTE, the degenerative brain disease notoriously plaguing a number of former NFL stars.

"The bottom line here really is the hits that count not the concussions," Dr. Lee Goldstein said.

The groundbreaking research, which comes out of Boston University, compared four brains of teen athletes with CTE and four brains of athletes with no evidence of the condition.

While recent major injuries to the athletes played a small role, they found it was the smaller, repetitive hits known as sub-concussive hits that were more significant in contributing to the crippling brain disease.

At 21 years old, Penn football star Owen Thomas committed suicide. ABC spoke with the family in 2012.

"I think if he didn't have CTE he wouldn't have committed suicide," his mother Katherine Brearley said. "I was just astounded that they found CTE."

Doctors found he had early stages of the degenerative brain disease even though he only suffered sub-concussive hits.

"It suggests that we don't have to wait years to decades to start seeing this type of injury to the brain," Goldstein said.

The risks are not just limited to football. They affect every athlete that plays contact sports, which begs the question - should we keep playing these games that are known to be dangerous?