Picture a fifteen-year-old girl in a neurologist’s office in Hannover, Germany, in the summer of 2021. She has been shouting the word “beans” involuntarily, sometimes hundreds of times a day, for the past three months. She hits herself in the chest, punches walls, throws crockery. The tics arrived within days of each other, fully formed. She has never had a tic before in her life. Her parents are terrified. The neurologist runs the standard tests. EEG, MRI, blood work, psychiatric screening. Everything comes back normal.
The girl in Hannover was one of a rapidly growing number.
Across 2020 and 2021, neurology clinics across Germany, Canada, the United States, Australia, and the United Kingdom began seeing the same presentation, with a frequency that was, at first, dismissed as coincidence and then, when the numbers kept climbing, dismissed as a strange but explainable consequence of pandemic stress. Teenage girls and young women, mostly between the ages of thirteen and twenty, arriving with abrupt-onset motor and vocal tics that looked, on first inspection, like severe Tourette syndrome. The tics were dramatic. They involved shouting swear words and offensive phrases, striking themselves and others, throwing objects, dropping to the floor. Many patients were being medicated for Tourette’s before anyone thought to ask a question the standard diagnostic pathway had not been designed to ask.
Which was: what have you been watching?
What the neurologists worked out
The person who worked it out first, and named the phenomenon in the medical literature, was Dr Kirsten Müller-Vahl, who runs the Tourette outpatient clinic at Hannover Medical School and had been one of the leading European researchers on Tourette syndrome for two decades. She and her colleagues began noticing that the tics arriving in their clinic did not look like Tourette’s. They did not follow the usual pattern of childhood onset, gradual escalation, and characteristic movement categories. They started overnight. They were dramatic in a theatrical way that Tourette tics almost never are. And when Müller-Vahl and her team looked closely, they noticed something else. The tics were the same tics. Not just similar. The same.
Patients across Germany were arriving with the same handful of vocal and motor tics as each other — the same words, the same gestures, the same self-directed movements. The tics did not match Tourette’s. They matched each other.
Müller-Vahl asked the obvious follow-up question. What she found was that almost every patient in the outbreak had been watching a small number of Tourette influencers with very large followings who documented their own tics on YouTube and TikTok. The influencer whose signature tics matched the German cohort most closely ran a YouTube channel with more than two million subscribers and, at the peak of the outbreak, a further large following on TikTok. He had a diagnosed mild form of Tourette syndrome. His most-repeated tic was shouting the word “beans.” Patients arriving at the Hannover clinic had, in most cases, been watching him for weeks or months. And the tics the patients had developed were the tics he performed on camera.
Müller-Vahl and her colleagues published what they had found in the journal Brain in August 2021, in a paper titled “Stop that! It’s not Tourette’s but a new type of mass sociogenic illness”. They proposed a name for what they were seeing. Mass social media-induced illness. It was, on the primary-source record, the first outbreak of mass sociogenic illness ever documented spreading via social media rather than through the physical proximity of a school, workplace, or community.
Within a year, follow-up studies confirmed the same pattern in multiple countries. A 2022 Frontiers in Psychiatry study by the same Hannover team examined 32 patients in detail. Most had been active on TikTok, YouTube, or both. Almost all improved when their social media exposure was reduced.
This video goes into the psychology of what happened:
Why this is not a new phenomenon, exactly
Mass sociogenic illness is one of the oldest documented patterns in medicine. Historians have traced examples back to the dancing plagues of medieval Europe, when whole villages spontaneously began dancing to the point of collapse and death. Salem in 1692. The nuns of Loudun in the seventeenth century. A group of teenage girls at a high school in LeRoy, New York, in 2011, who developed Tourette-like tics with no organic cause. In every case, a group of people, almost always young, almost always female, and almost always emotionally connected to each other in some way, develop the same physical symptoms in rapid succession, and the symptoms cannot be explained by any physical illness the medical system knows how to diagnose.
The standard explanation, refined across decades of research on the phenomenon, is that mass sociogenic illness happens when a group of stressed, socially connected people are exposed to a symptom template that the brain and body can, in a real physiological sense, adopt without any conscious decision to fake anything. The symptoms are genuinely experienced. They are not consciously produced. They are also not the result of any measurable damage to the body or the nervous system. What has changed is the interpretive layer through which the body’s ordinary background signals are being processed.
What made the 2020–21 outbreak different from every previous outbreak in the medical record was that the socially connected group was not, in this case, a group of nuns in a convent or a group of girls at the same high school. It was a group of teenage girls, dispersed across four continents, who had spent the pandemic year watching the same handful of creators on the same handful of apps, in isolated bedrooms, with no direct social contact between any of them.
What the algorithm had done, without anyone particularly designing it to do so, was assemble a virtual convent.
What the outbreak was pointing at
The uncomfortable finding from the follow-up research is that the tics were the visible presentation of something deeper. According to the work published by Dr Tamara Pringsheim and colleagues at the University of Calgary in Movement Disorders in August 2021, patients presenting with the outbreak had approximately four to five times the odds of a co-existing anxiety or depressive disorder compared with patients presenting with primary tic disorders (odds ratios of 4.42 for anxiety and 4.92 for major depressive disorder, controlling for age and sex). The tics were not appearing in random teenagers. They were appearing in teenagers who had, in most cases, already been struggling with mental health difficulties that the pandemic had made significantly worse.
What the videos of Tourette influencers were providing, on the strongest reading of the clinical picture, was not just a symptom template. It was a community. Patients had, in many cases, been engaging for months with online groups of other young women who shared the same tic-like symptoms, who supported each other, who understood what they were going through, who legitimised their suffering with a clinical-sounding name. The tics were, in an odd and painful way, giving them something they had not been able to find elsewhere: care, recognition, a place to belong. This is not the same as saying they wanted the tics or produced them for secondary gain. Functional symptoms of this kind are physically real to the person experiencing them, and the involuntary quality is genuine. It is the underlying picture of unmet need — of anxiety, of isolation, of a search for community — that the tics were sitting on top of.
Which meant treatment was complicated. Telling patients to stop watching TikTok was not enough. What clinicians had to do was find something else that would meet the underlying need. In most cases, that meant proper psychiatric treatment for the underlying anxiety or depression, family involvement, and a gradual reduction in social media exposure over months rather than weeks. Where those things were put in place, most patients recovered. Where they were not, some patients continued to worsen.
The outbreak has, in the years since, become something of a case study in what social media can do to a vulnerable adolescent nervous system when the conditions align. The claim is not that TikTok or YouTube is doing something to teenagers that would not have happened anyway. The claim is that when large numbers of teenagers with pre-existing mental health difficulties spend an isolated pandemic year watching the same content, delivered by the same algorithm, the platform becomes something more than an app. It becomes the mechanism through which a very old human phenomenon — the tendency of a stressed group to adopt a shared physical response to that stress — can now propagate at a speed and scale no previous outbreak in medical history has ever managed.
One further complication is worth naming. The influencers themselves were not, in most cases, malicious actors. The most-followed of them had a diagnosed neurological condition and did not set out to cause anyone else’s symptoms. What the outbreak makes visible is a systemic pattern — the interaction between a real condition, an engagement-optimised platform, an isolated and vulnerable audience, and a pandemic year that removed most of the alternative sources of connection those teenagers might otherwise have found.
The girl in Hannover, and the young people like her, mostly got better. Most stopped watching. Most found something else. The Brain paper that first described what was happening to them has been cited more than four hundred times, and the follow-up literature is now working on the broader question of what platforms optimised for engagement do to the developing minds using them. The tics were the visible symptom. The condition beneath them is what the medical literature is still learning how to describe.
Kiran Athar is not a psychologist or a neurologist. She writes about psychology, mental health, and the everyday corners of life where the two intersect, drawing on peer-reviewed research and primary-source scholarship. This piece discusses self-harm behaviours and mental health difficulties in adolescents. If you or someone in your life is struggling, help is available: in the United States, dialling 988 connects to the Suicide and Crisis Lifeline; in the United Kingdom, Samaritans can be reached on 116 123; national equivalents exist in most countries.
