Within the first several months of the COVID-19 pandemic, doctors around the world noticed something strange. Suddenly, they were seeing a surge of young patients presenting with sudden, explosive tics.

But in many cases, these tics didn’t fit the profile of a tic disorder like Tourette Syndrome. Doctors started searching for a shared source that was causing the outbreak, and that search led them to TikTok.

Experts at the University of Calgary have been leading the research.

Azeen Ghorayshi is a reporter with the New York Times. Today, she takes us through what researchers have found about why so many teens were affected, what the pandemic had to do with it and the role social media played in the spread.