World Cup fever is cooling down, and it’s clear that soccer has taken hold in American society. The sport has become hugely popular among people of all ages, and for good reason: it’s inexpensive, vigorous and fun. Yet similar to football, soccer can also damage your child’s brain.

Although we don’t consider soccer a “contact” sport, it is. An object flying at up to 75 miles per hour meeting with one’s cranium is most certainly “contact.” Heading soccer balls—which a player does an average of 12 times a game—has been linked to poor cognitive performance, brain abnormalities and many behavioral issues. In my new book, “Change Your Brain, Change Your Life (Before 25),” I write about Ethan, a bright and popular 15-year-old who ended up in my office with his mom. She was convinced that Ethan’s plummeting grades and increasingly negative, impulsive behaviors were the result of drug use.

I asked Ethan if he played any sports. “Yes,” he said. “Soccer.”

“Have you had any concussions from playing soccer?” I asked. I quickly saw from their reactions that he had.

At age 11, Ethan’s youth soccer coach thought it would be great to have young players practice headers for a full 45 minutes, nonstop. That night, Ethan complained of headaches and dizziness. His parents headed to the ER, where a number of his teammates had preceded him, all suffering from similar headaches.

It wasn’t until Ethan and his mom saw his brain scans—showing injury, flattening and damage to his prefrontal cortex, the area of the brain in charge of attention, focus, impulsivity, planning and organization—that they admitted that the culprit was probably soccer. Specifically, a poorly informed soccer coach who didn’t realize that young brains are fragile and shouldn’t collide with leather balls for 45 minutes straight.

Ethan is doing well now, but I often wonder how many other youngsters aren’t. I wonder how many may be suffering from some kind of undiagnosed traumatic brain injury related to too much head contact, at too young an age. And how many parents think that the reason for their son or daughter»s seemingly uncharacteristic behaviors is illicit drug use or some other form of mental illness?

I realize that by questioning the safety of such a popular sport, I risk the wrath of die-hard soccer fans. So I’ll be clear: Am I saying to that you should pull your kid out of youth soccer? No. The last thing we need in this country is more sedentary kids. Soccer is a health and fitness-promoting activity—a beneficial game for children in many ways. But part of health is a healthy brain. Coaches should teach proper form for heading a ball; and better yet, try to avoid it entirely with elementary and middle school players. Talk to your youth league officials; talk to your child’s coach.

To paraphrase the admonishment often directed at players whose attention has wandered while on the field: “Keep your head out of the game!”