McKelvey School of Engineering School of Medicine

Predicting the chaos in Tourette syndrome tics

During the pandemic, news reports surfaced of a surge of young adults showing up at doctors’ offices with unexplainable movement disorders that looked, perhaps to a nonspecialist, a little bit like Tourette syndrome.


But when those patients were sent to see a specialist, “They’d say, ‘that doesn’t look at all like any of my first thousand patients,’” said Kevin Black, MD,  a professor of psychiatry at Washington University School of Medicine in St. Louis. People with experience knew that there were telltale properties of the tics associated with Tourette’s, even though there is no one tool that allows a doctor to give a diagnosis on the spot.


However, research published Feb. 23 in the Journal of the Royal Society Interface by Black and Rajan Chakrabarty, PhD, the Harold D. Jolley Career Development Associate Professor of Energy, Environmental & Chemical Engineering at the university’s McKelvey School of Engineering, may signal that a diagnostic tool is near.

They have replicated and expanded on previous work to show that tics associated with Tourette syndrome have a fractal pattern. They also discovered that a key characteristic of that pattern in any individual can predict how severe the disease will become.

Specialists had long suspected there was some kind of pattern to tics associated with Tourette’s, and in the late 1990s, a seminal paper by Bradley Peterson and James Leckman was able to uncover that pattern — but only over a period of seconds to minutes.

Black, a neuropsychiatrist who specializes in movement disorders, has been heading a research study on tics for years. As part of the New Tics Study, he had collected an impressive amount of data about tics in children as they were going through the yearlong diagnosis process.

He had all that data — nearly 1,000 minutes of footage documenting the timing of tics in 78 kids taken in two sessions, a year apart– but he needed a help of a complex systems scientist to figure out what the noisy datasets were telling him. He reached out to Chakrabarty. “My initial thought was, ‘Let’s just see if we can replicate Peterson’s finding,’” Black said.

Chakrabarty is an aerosol scientist and an expert in studying chaos and patterns in complex environmental systems; examples include studying the chaotic transport properties of pollution particles as they move through air under the influence of everything from wind to humidity to sunlight.

“Tics are chaotic,” Chakrabarty said. “Tics are a kind of chaos in human biology, in our neural networks.” His lab turned to the tools he uses to find the patterns in the chaos of aerosol systems.

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