Last summer, 17-year-old Eliza began experiencing mild but uncontrollable tics. Her nose would twitch, her eyes would shut and squint. By August, she had been diagnosed with Tourette’s syndrome, and had started developing vocal tics. “I’m more fortunate to not have severe tics, or at least I haven't developed any serious tics yet if I can put it that way,” she says. “But there are people that are suffering, and who try to raise awareness.”

Many of them post on TikTok: videos tagged with #tourettes have been seen more than three billion times, with users demonstrating how they go through everyday situations with the syndrome. One shows a schoolgirl struggling to handle a Covid test while she suffers a series of tics; others feature British father Glen Cooney, known on the app as @this.tourettes.guy, who has nearly three million followers.

These positive representations of Tourette’s have helped to normalise a neurological condition that affects an estimated 300,000 people in the UK. Cooney, 42, spends hours every day answering between 50 and 60 questions he receives via TikTok and Instagram messages from anxious parents and children who believe they may have Tourette’s.

It’s a far cry from his childhood in the late 1980s and early 1990s, when he developed tics after his cousin was killed at the age of 11 on their way to school. “My dad was quite abusive and used to tell me to stop doing it,” he explains. “I got forced to hide it for years and years, because if I said all these things and did all these twitches, I’d get in trouble for it at home.” He was labelled as disruptive at school, which got him into more trouble. “It was hard back then, and it’s still hard now for kids,” he says. “But people who didn’t know it from before are now taking their children to get diagnosed with it because of something I’ve done. I think that’s fucking amazing.”

But the rise of Tourette’s content on TikTok has also sparked a controversial medical debate. Earlier this month, doctors at Great Ormond Street Hospital for Children warned in the British Medical Journal (BMJ) that they were seeing a significant rise in the number of teenage girls – who ordinarily have Tourette’s at a much lower level than boys – in the early months of 2021.

The physicians cautioned “there is some concern that social media and websites such as TikTok that promote the sharing of videos of influencers with symptoms may have a part to play." Others researching Tourette’s and tics responded, saying we could be seeing a 21st century equivalent of the Middle Ages’ “dancing mania”, when people began suffering from attacks of spontaneous dancing which has little cause. (None of the authors of either BMJ paper responded to requests for comment.)

This is still just a theory – and it’s unclear what the mechanism for such a phenomenon might be, or how it would fit into our limited understanding of the causes of Tourette’s syndrome.

Suggestibility could be one root cause, says Uttom Chowdhury, who works in an NHS community clinic focused on tics and Tourette’s in Bedfordshire. His clinic has seen an increase in the number of referrals for teenage girls – unusual given Tourette’s usually affects boys, and usually presents at an early age of five or six, rather than 14 or 15. “These girls who are presenting did not have a family history [of tics], so there’s something different about this cohort,” he says. (Around 50 per cent of those with Tourette’s are likely to pass it on to their children, according to one analysis.)

“There’s a sense of reassurance. But then you do wonder if it’s providing the psychological need,” Chowdhury continues. “Experts and clinicians know there’s suggestibility. If I have a patient in my room and say 'Do you have a tic in your head or neck?', sooner or later they’ll tic.” It’s similar, he says, to the temptation many of us feel to blurt out an objection at a wedding when asked by the minister if there’s any reason why these two people shouldn’t be married. “If they see something, it’s very easy to copy, there’s that suggestibility. Watching these videos could be making people copy it as well,” he says.

Suzanne Dobson of Tourettes Action, a UK charity that supports those who have Tourette’s, and funds research into it, agrees. But she questions whether the immediate feedback of social media is actually eliciting new tics, or just encouraging people to be more open about their existing ones, so they're straining less to tamp them down. “Young women film themselves doing their tics, and post it on TikTok and say: ‘What is happening to me?’ People say, ‘Maybe it’s Tourette’s’, but they get a lot of likes. They gather followers. And so, as their tics become more extreme, the more they post, the more they look for reassurance from their peer group, and the more the negative feedback loop perpetuates.”

It’s impossible to pin the blame on social media. One of the main causes for Tourette’s is believed to be anxiety – and we’re not exactly living in normal times right now. Tourette’s is a “functional illness,” says Chowdhury – it has a purpose, which might be to release anxiety or let off steam. Had those already anxious teenagers, worried about the spread of the pandemic, not seen people with Tourette’s on TikTok, their anxiety may have just manifested itself in a different, potentially more damaging, way.

Neither Chowdhury or Dobson – or anyone else, including the specialists exchanging theories in the BMJ – can say for sure whether TikTok is the chicken or the egg in this situation. “There may be a cohort of people who are very suggestible,” says Chowdhury. “In the same way there was hysteria in different centuries, there’s outbreaks of tics. We don’t know enough, and I’m not saying this is hysterical or made up. I always keep an open mind on it.”

What is clear is how Tourette’s content is helping people with the condition in ways that didn’t happen in the past. “Back in the early 1800s, people with tics were shut away by their family,” Dobson says. “That’s barbaric. It’s not about isolating these young women, but it’s about giving them appropriate support, and people understanding what’s happening to them.”

One of Chowdhury’s most recent patients is a 13-year-old who first began noticing tics when she returned to school after lockdown ended. She was different to many patients the specialist had seen before. “Although she had all these tics and it looked uncomfortable, there was a confidence in her,” he says. “She said: ‘I’ve looked it up and researched it’.” That included on TikTok. “A bit of me was thinking that was good, she’s looked it up and researched it,” he says.

Cooney wasn’t diagnosed with Tourette’s until he was in his 30s. He, his wife, and his daughter were watching The Undateables on television when they pointed out that he was just like a contestant who had Tourette’s. Had TikTok been around back then, his life may have been different. “I may have been one of those kids whose parents spotted someone like me online,” he says. “I would have been sorted way back then. It would have saved a lot over the years, trust me. I’ve lost friends over this, I’ve been in fights over it.”

“To see yourself represented is a good thing,” says Chowdhury. “If you’re a kid with tics, it’s a lonely world. I don’t know whether it’s causing it or making it worse, but I do like the fact it’s educating people.”

That’s why Eliza eagerly supports anyone who presents their tics on TikTok. “It helps me a bunch,” she says. “Tourette’s is such an uncommon thing, and seeing people with it makes me happier. It makes me feel human again.”