Doctors around the world believe a rise in cases of tics in young girls are the result of watching TikTok videos about Tourette syndrome.
The condition causes people to develop symptoms like sudden twitches or noises - but hospitals are reporting an increase in teenage girls coming in after developing similar behaviours, according to People.
Experts say this is unusual as tics are more common in boys than in girls.
Canadian, American, British and Australian experts studied patients for months and found that a common factor among all the girls was their interest in watching TikTok creators who talk about having Tourette syndrome, according to the Wall Street Journal.
Texas Children's Hospital reported 60 cases of teen girls being admitted with tics since March 2020, compared with just one or two the previous year.
And other researchers from children's hospitals around the world found that referrals for these behaviours climbed during the pandemic, particularly in girls aged 12 to 25.
They wrote that they saw a "similarity between the tics or tic-like behaviours shown on social media and the tic-like behaviours of this group of patients".
Doctors from Rush University Medical Centre looked at TikTok videos tagged "tic", "Tourette" and "tourettes,", writing that they "believe this to be an example of mass sociogenic illness", in which people copied the behaviours they saw in the videos.
They even called the Tourette TikToks a "pandemic within a pandemic".
Rush movement-disorders fellow Caroline Olvera told the publication that several teen girls had a tic causing them to say "beans" in a British accent. She started watching Tourette videos on TikTok and found that a top influencer with Tourette syndrome was British and would often say "beans".
It's not likely that the teenagers are actually developing Tourettes itself, but a functional movement disorder able to be resolved with therapy.
Doctors also found that many of them had previous diagnoses of anxiety or depression, which intensified amid the pandemic.
Their recommendation to parents seeing these behaviours in their teens is to encourage their kids to take a break from social media or block Tourette videos on their TikTok account.
Resisting the urge to overreact and trying to help their kids keep a normal routine will also help, they said.