Although the evidence for these sex differences has grown over the last few years, some experts would prefer to see these results replicated with further, carefully controlled studies, before the message is widely shared.

Without that corroboration, they worry that inadequately supported public claims may inadvertently harm women’s recoveries. As Melissa McCradden, a neuroscientist and former competitive athlete, argued in a piece for Scientific American in 2017, a patient’s own expectations can influence their progress. “So if we label women in this way, it can have a direct, negative effect on their recovery from concussion,” she wrote.

There is also the fear that this information might put males at greater risk, if they wrongly assume that concussion is only a female problem.

“If you focus too much on any kind of perceived or possible male-female divide, it might give this false perception that actually males are more able to withstand concussion [than they really are],” says Luke Griggs, the deputy CEO of Headway, a charity that offers support for the survivors of brain injury and their carers across the UK. Boys and men might believe they could return to play too early – whereas everyone, he emphasises, should be cautious following a concussion rather than trying to ignore their symptoms.

These are reasonable concerns, but many with concussion have been frustrated by the current lack of awareness about their condition.

Esther told me that some of her doctors were aware of the sex differences. But she would have preferred to know herself, before she ever got concussed. “I had no idea,” she says. “And I think that if you’re an athlete, playing any sport, you deserve to know the potential risks. If you’re a girl playing sports, you deserve to know that maybe you are more at risk than your male counterparts.”

Esther and Jessica emphasise that they wouldn’t have let the risks prevent them from playing the sports in the first place – this should not be taken as another excuse to limit the potential of girls and women. But they hope that female athletes would benefit from having the knowledge to protect themselves from unnecessary injuries and to ensure that they do not feel pressured to return to play too quickly, for instance.

Better awareness of these sex differences could ultimately lead to better care before and after the event.

One strategy might be to build better headgear for women. Unfortunately, it’s not quite that simple: concussions can arise from the sudden movement of the head as well as from a direct blow to the skull, which means that headgear won’t prevent certain causes of concussion (though it can prevent fractures and other head injuries).

Some researchers are taking another approach: designing special exercises which could strengthen female neck muscles, which could reduce the violent movement of the head following an impact. “It could decrease the basic chance for [concussive] brain injuries,” says Inga Koerte.

And if further research shows that the sudden drop in progesterone increases the risks, then it might be a reason for female athletes to take oral contraceptives (though the evidence is not yet strong enough to make this recommendation).

For Jessica, these measures will be too late. She now lives and works in the UK, and after three years, many of her symptoms have subsided enough for her to “mostly live my life without too much trauma”, she says, but she still has a constant lingering headache, and she has to be on constant watch-out for a “flare-up” – which can occur whenever she has over-exerted herself. And small difficulties that she once could have easily managed continue to feel overwhelming.

Indeed, on the day we were due to speak, she had been making some sales forecasts for work. She says it was hardly “rocket science”, yet she soon felt the fog descending.

“I was looking at those numbers, and nothing made sense – like I couldn’t [even] figure out where to start to have them make sense.”

She is still unable to play her beloved roller derby, and even running – with its repeated jolting movements reverberating through the body – is too much to bear, though she has recently taken up climbing, which doesn’t lead to flare-ups. Without any answers from conventional medicine, she’s sought help from acupuncture and osteopathy.

More than anything, the experience means that Jessica is constantly conscious of her brain’s physical presence and its vulnerability. “I mean, you’re normally not aware of your brain. It’s just there – it’s like your feet, it’s like breathing. But for me, I’m always aware of it.”

Wellcome, the publisher of Mosaic, supports research into neuroscience and funds a Research Fellowship in Humanities and Social Science around concussion and dementia in sport.