For years, soccer was Joanna Roy's life.

The 17-year-old began playing the sport at six, but was forced to stop after suffering a severe concussion from heading a ball.

"Not only was it my favourite thing to do, it was the thing that I did every single day. It was my life," said Roy, who spent more than a year recovering from the concussion. "It was how I spent my spare time. I never knew anything else."

Doctors have long raised concerns over heading in soccer and the possibility of traumatic effect on players' brains. A new U.S. study, however, shows female players may be more vulnerable to brain injuries from repeated heading.

Conducted by the Albert Einstein College of Medicine in New York, the study of 49 male and 49 female amateur soccer players found that on average, the volume of damaged brain tissue was five times more extensive in women than in men. Both groups were in the same age range and reported a similar number of headings in the past year.

Roy, a lifelong soccer player, had to stop after a hard header led to a concussion' 1:11

Study leader Dr. Michael Lipton said while female players have been known to fare worse following head injuries, some have suggested that is because women are more willing to report symptoms. However, this research measured objective changes in the brain through diffusion tensor imaging, a type of magnetic resonance imaging.

"This finding from an imaging study has nothing to do with what the players report, it's what we actually measure in their brain tissue," Lipton said.

Scanning brain structure

The scans measured the diffusion of water in deep brain tissues that co-ordinate communication between brain regions. The more uniform the diffusion of water, the better micro-structural integrity of the tissue, the study said.

Imaging by the Albert Einstein College of Medicine shows areas of microstructural abnormality in male and female players' brains. The areas in blue on the template brain are the regions that suggest damage from heading. (Todd Rubin/Albert Einstein College of Medicine)

The assessment found that the women studied had an average of eight regions of the brain where greater levels of heading resulted in damage, compared to only three regions in men.

Researchers have still not confirmed why women might be more vulnerable to head injuries. They speculate it may be caused by differences in neck strength, hormones or genetics.

In 2014, researchers at Toronto's St. Michael's Hospital also found a higher incidence of concussions among female soccer players — for what they believe are similar causes.

Trying to understand risk

Lipton was clear that one heading does not necessarily result in immediate injury.

"In fact, it's remarkable that the brain seems to be pretty resilient to low levels of heading. What we need to do is find out what the thresholds are that confer a risk," he said.

The solution? Rather than ban heading altogether, which Lipton said is unlikely to happen and may be unnecessary, he would like to gain a better understanding of how the impact of heading the ball accumulates and causes damage.

"Once we find out where that level is, what these findings are suggesting is it's likely that the threshold may differ between men and women — and women may need to limit the amount of heading they do more than men."

Prioritizing safety

Veteran youth soccer coach Carolyn McCaughey says her priority is the safety of her young players.

"I've played the game for a long time. I've headed the ball for a long time — so I see that side of it. But I'm also a mother with a daughter who I want to stay safe in the game," she said.

Carolyn McCaughey is a veteran youth soccer coach. She says there are no restrictions on young soccer players heading the ball in Canada. (CBC)

She said if research shows cause for concern around heading, that's something regulatory bodies should consider.

"If there's data to say we shouldn't do this, it's something policy-makers need to look at and impact how we teach and possibly, how we play."

The research extends beyond Lipton's new study.

Dr. Paul Echlin, a primary care sports medicine specialist at Ontario's Elliott Sports Medicine Clinic, said research over the years has confirmed that heading is the main culprit for soccer-related brain trauma, not the incidental head to ground or head to post injuries.

"We now know because of MRI and advanced MRI imaging and analysis that it does cause trauma and that can't be ignored."

Researchers have yet to fully understand why women might be more vulnerable to head injuries. (Jean-Pierre Clatot/Getty Images)

In 2015, the U.S. Soccer Federation implemented a ban on heading for players 10 and under and restrictions on the practice for players aged 11-13. Canada's governing body for soccer recommends coaches not teach younger players heading, but it does not currently have formal age restrictions on the practice.

But for Roy, whose soccer career has ended due to header, a ban on heading is not the solution. She said there should be more of an emphasis on teaching the proper form for headers.

"Regardless of whether it's allowed or not, people are going to do it and if it's allowed, then people will learn how to do it properly. I think that can help reduce injuries."