In October 2011, something very strange happened at a high school in upstate New York. Over the course of the following months, around 18 people at the Le Roy Junior-Senior High School started to experience uncontrollable twitching, spasms, and verbal tics – much like the symptoms of Tourette's syndrome. Except for one boy and one older woman, all of the affected people were teenage girls attending the school. 

By early 2012, the sensational story had hit the mass media, with news articles appearing everywhere from the New York Times Magazine to Reuters, as well as a number of high profile TV cable news shows such as Good Morning America, The Today Show, CNN, and Dr Drew. Many of the girls widely shared videos of their unusual symptoms on Facebook and YouTube, spurring waves of attention on certain corners of social media. 

As per Newsweek, the story even caught the curiosity of Erin Brockovich, the activist depicted in the 2000 Julia Roberts film, after there was some speculation it could be linked to a 41-year-old chemical spill a few miles from the school. Others blamed a nearby fracking site, or suspected it could be the side effect of a vaccination. 

Together with the school, the New York State Department of Health, the New York State Department of Environmental Conservation, and the Environmental Protection Agency swooped in to get to the bottom of the case. However, most of their avenues of inquiry quickly closed. Reuters reported that the school and the area around it were tested, while other agencies collected soil samples, but the investigation by state health authorities found that environmental factors were not a factor. Latent side-effects from drugs or vaccines were also ruled out, as were genetic factors.

Eventually, Dr Laszlo Mechtler, a neurologist from the Dent Neurologic Institute who treated most of the girls, came to share their diagnosis: the students were experiencing a form of conversion disorder and mass psychogenic illness, also known as mass hysteria. This is a psychological phenomenon in which a group of people within a certain community or population subconsciously copy behavior or pick up similar symptoms, often in response to trauma or a perceived threat.

Some of the girls’ parents were not happy with this diagnosis, however, as they felt it suggested the serious symptoms were simply “in their heads.” Furthermore, some accused the school and health authorities of a cover-up, maintaining that some kind of environmental factors sparked the girls’ condition. 

By summertime, many of the students’ symptoms improved, and most had returned to “normal life”. However, it turned out that one of the girls was diagnosed with Tourette's syndrome, a neurological condition characterized by repetitive, involuntary movements and vocalizations called tics. Dr Mechtler suspects that this one case may have somehow set the tone for the collective psychological phenomenon that followed.  

“We noticed that the kids who were not in the media were getting better; the kids who were in the media were still very symptomatic,” Dr Mechtler said, per Reuters. 

“One thing we’ve learned is how social media and mainstream media can worsen the symptoms,” he said. “The mass hysteria was really fueled by the national media, social media - all this promoted the worsening of symptoms by putting these people at the national forefront.”