As many as 3.8 million concussions are reported every year.
Most people think of male athletes when they think of concussions - but new research is showing young women may be more likely to suffer this injury.
Claire Stieg has a passion for horses. She's been riding since she was a little girl.
But at age 14, Stieg's favorite sport turned dangerous. While playing polo, she was thrown from her horse.
"I hit the ground so hard that I blacked out and had a seizure," she said.
Stieg suffered a concussion, and she isn't alone. Recent research shows female athletes get just as many - if not more - concussions as males.
"Typically, concussions occur around some event when you receive a blow to the head," said Philip Stieg, MD, chief of neurosurgery at New York Presbyterian/Weill Cornell Medical Center.
One study found high school girls who play soccer are 68 percent more likely to have a concussion than boys.
In sports played by both genders, girls are reporting nearly twice as many concussions - and studies have shown girls take longer to recover from concussion symptoms.
"They can have headaches; they can have sleep disorders, appetite disorders and cognitive disorders," Dr. Stieg said.
Doctors are still trying to figure out why more females are being affected.
A reason may be that girls neck muscles are less developed making them more susceptible to head shaking and secondary concussion.
"Women are more likely to report they've had concussive injuries than men," Dr. Stieg said.
Stieg suffered headaches and was extremely tired after her concussion. But after two weeks of rest, she felt better - and is now playing college polo!
"I wasn't afraid to get back on the horse. I really wanted to get back on and ride," Stieg said.
Dr. Stieg says most concussions resolve themselves within seven days but if you are still having symptoms like headaches or trouble sleeping, you should see a doctor immediately.