(Jonathan Newton / The Washington Post)

A new study has linked high school football to changes within the brain, even in players who have never had a concussion.

Repetitive hits showed changes that appear to be abnormal, according to Christopher Whitlow, the study’s author and an associate professor at the Radiology Translational Science Institute at Wake Forest Baptist Medical Center. “It’s not the harder the hit,” Whitlow said (via Newsday), “it’s the cumulative exposure to impact.”

Concussion awareness has been growing in the NFL, with studies of former players revealing cognitive issues and dementia as well as chronic traumatic encephalopathy. The apparent suicide of Ohio State player Kosta Karageorge over the weekend, brought the dangers of multiple concussions back into the conversation. “He had a pretty bad concussion last fall and he told me about differences in his behavior,” his sister, Sophia Karageorge, told the New York Times. “Just, like, confusion, disorientation, being unable to focus, mood swings — not feeling like himself, basically, not feeling quite right.”

The study, also published the Journal of Neurotrauma, was limited to 24 players who have never had a concussion and are between the ages of 16 and 18. The players who were studied wore devices in their helmets that measured how often and how hard they were hit during practices and games. “There’s a lot we don’t know about these changes. Do they persist over time? Do they go away? Are they associated with some subtle cognitive changes?” Whitlow said (via Bloomberg). “We haven’t really answered those questions yet, but are planning to in the future.”

Awareness is increasing in older athletes, like those in college and the pros, but the high-school level and below is another matter.

“We know little about head injury risks for those youth football players,” Whitlow said. “If we can identify risks, then we can intervene, decrease the risks, and make this sport as safe as possible for all the children who are playing it.”

Newsday’s Mary Elizabeth Dallas described the new study’s methodology:

[P]players were divided into two groups. Nine of the athletes were considered heavy hitters, and 15 were considered light hitters.

Using an advanced brain imaging technique, known as diffusion tensor imaging (DTI), the researchers then looked for changes in the white matter of the players’ brains.

White matter is made up of millions of nerve fibers that work like communication cables connecting various parts of the brain. DTI provides a measurement of the movement of water along these nerve fibers, known as fractional anisotropy (FA).

In a healthy brain, the movement of water is even and has high FA. More random water movement and a drop in FA, however, suggest brain abnormalities.

Although none of the players sustained a concussion, by the end of the season the players in the heavy-hitter group had more significant decreases in FA in certain parts of the brain than those in the light-hitter group, the researchers noted.

The study’s conclusion? More long-term studies are needed. In the meantime, the nearly 3 million high school football players in the U.S. need better helmets and increased education for trainers, coaches and parents.