Aidan’s tics erupted one day after school in early 2021, about a month after the pandemic lockdown had ended. The 16-year-old convulsed while walking into the house, head snapping and arms swinging, letting out high-pitched whistles.

Aidan’s parents looked up from the living room couch with alarm. They had been worried about the teenager’s ratcheting anxiety — related to COVID-19, gender dysphoria, college applications, even hanging out with friends. But they were not prepared for this dramatic display.

“We watched this happen in front of our eyes,” Aidan’s mother, Rhonda, recently recalled.

They rushed Aidan to the emergency room, but doctors found nothing wrong. After calling a neurologist, the family learned that more than a dozen adolescents in Calgary had recently experienced similar spasms.

Over the next year, doctors around the world treated thousands of young people for sudden, explosive tics. Many of the patients had watched popular TikTok videos of teenagers claiming to have Tourette syndrome. A spate of alarming headlines about “TikTok tics” followed.

But similar outbreaks have happened for centuries. Mysterious symptoms can spread rapidly in a close-knit community, especially one that has endured a shared stress. The TikTok tics are one of the largest modern examples of this phenomenon. They arrived at a unique moment in history, when a once-in-a-century pandemic spurred pervasive anxiety and isolation, and social media was at times the only way to connect and commiserate.

Now, experts are trying to tease apart the possible factors that made these teenagers so sensitive to what they watched online.

Four out of five of the adolescents were diagnosed with a psychiatric disorder, and one-third reported past traumatic experiences, according to a study from the University of Calgary that analyzed nearly 300 cases from eight countries. In new research that has not yet been published, the Canadian team also found a link to gender. The adolescents were overwhelmingly girls, or were transgender or nonbinary.

Perhaps as striking as the wave of TikTok tics is how quickly it has receded. As teenagers have resumed their pre-pandemic social lives, new cases have petered out. And doctors said that most of their tic patients had recovered, illustrating the expansive potential for adolescent resilience.

“Adolescence is a period of rapid social and emotional development,” said Dr. Tamara Pringsheim, a neurologist who co-led the studies in Calgary.

“They are like sponges, grabbing on to new skills to cope.”

Pandemic crash

Aidan had always been a sensitive child. At 6, during a turbulent period for the family when their mother was ill, Aidan began to occasionally tic, clearing their throat or rolling their eyes. (The family asked to be identified only by their first names because of privacy concerns.)

Aidan was raised as a boy. By adolescence Aidan came out as bisexual and traded sports for ballet and theater. Aidan was severely bullied. Once, their skull was cracked after being dragged by the ankles into a shower in the boys locker room.

In high school, Aidan came out as nonbinary and began using “they” and “them” pronouns. They grew out their hair and occasionally wore skirts to school, trying to figure out what felt right. Their parents, while supportive, were worried about the changes, making Aidan feel angry and unsettled.

The teenager took refuge in drama class, where being different was encouraged. But in retrospect, Aidan realized that the group glamorized mental illness, sometimes flaunting psychiatric diagnoses.

“It was like a weird fetishization of sadness,” said Aidan, now 18.

When the COVID-19 lockdown was announced, Aidan felt a tinge of relief. Online school allowed the teenager to fly under the radar, drawing or watching videos on their phone.

On TikTok, they found scores of teens who were sharing their experiences with all kinds of health issues, including dissociative identity disorder and Tourette syndrome.

But when school reopened in January 2021, Aidan’s stresses came flooding back. Seated in class one afternoon, the teenager sent their parents a long text message with an urgent request.

“I think I should see a therapist,” Aidan wrote. They had started having panic attacks, they said, sometimes pulling at their skin while struggling to breathe. Their social interests were narrowing as they spent more time on their phone.

Aidan started therapy soon after. But in a month, the convulsions began.

Tic influencers

Around the time Aidan started to tic, Pringsheim and Dr. Davide Martino, movement specialists at the University of Calgary, saw a message in an online forum for the American Academy of Neurology.

“My practice has seen an unprecedented increase in young adolescent women with what appears to be acute explosive motor and vocal tics,” wrote a doctor in Kansas City, Missouri.

The Canadian neurologists had seen the same thing. Most of these new patients did not fit the mold of a typical case of Tourette syndrome, which generally affects boys and begins in early childhood.

Tourette’s tics tend to be simple movements — like blinking or coughing — and they wax and wane over time.

In contrast, the new patients were often rushed to the emergency room with tics that had appeared seemingly overnight. They were relentless, elaborate movements, often accompanied by emotionally charged insults or odd phrases.

The matching accounts from physicians around the world made the neurologists suspect a shared source. Pringsheim’s teen daughter suggested that they look at TikTok, which is used by more than two-thirds of U.S. teenagers.

When they searched for “tic” and hundreds of videos popped up, Pringsheim was stunned.

“This is the person that I saw in my clinic today,” she recalled thinking.

Road to recovery

In August 2021, after missing six months of school, Aidan was offered a coveted spot at a small rehabilitation clinic for functional disorders at Alberta Children’s Hospital. Aidan was constantly lurching, hitting themselves and shouting obscenities. “I hate you!” they often yelled at their mother. “Pay me!” “Beetroot!” “I’m a silly goose!”

At the heart of the rehab program was a cognitive- behavioral approach that addressed the psychological root of the problem and helped patients develop coping skills. They had to accept two things: that they did not have Tourette syndrome, and that their twitches were partly under their control. They had to want to get better.

For eight to 10 hours a week for six months, Aidan met with a speech therapist, a dietitian and a psychiatrist. In therapy, they discussed getting bullied, stress over gender and how isolated they had become during the pandemic. They deleted TikTok and started antidepressants.

Aidan finished the program and returned to school. They wrote and directed a play, and graduated on time, with honors.

Aidan hasn’t had a tic in a year. They no longer use TikTok — not because they’re afraid of getting sick, but because they find it boring.

Aidan has learned to better identify and manage their anxiety. With the support of their psychiatrist, the teenager is planning to wean themselves off antidepressants early next year. Their stress about gender has also faded. They believe that the tics were a byproduct of an earnest, if futile search for definitive answers about their mental health and identity.

“After a year of therapy, I came to the conclusion that labels are stupid,” Aidan said. “I’m just out here.”

Neurologists said that a majority of the adolescents who developed tics during the pandemic — even those who did not have intensive treatment like Aidan — have stopped twitching.

Although Aidan’s illness derailed their lives for a year, Aidan and their parents said the experience pushed them to grapple with painful family dynamics that predated the pandemic. “We’re closer than we were before,” Rhonda said.