Audience
Individuals with Tourette Syndrome or another Tic Disorder, families and caregivers, researchers, clinicians, and other community members
Selection Bias and the Natural History of Tics
Explore the science, explained clearly by a researcher. Dr. Kevin J. Black will dive into evidence that Tourette Syndrome and Provisional Tic Disorder are far more common and longer lasting than suggested by clinic-based samples, with roughly half of children showing observable tics at some point in elementary school and at least one quarter—likely more—meeting criteria for a chronic tic disorder, although only a minority experience clinically meaningful impairment or ever receive a diagnosis. Dr. Black argues that selection and ascertainment biases at every step—from who tics, to who is noticed, brought to medical attention, enrolled in studies, and followed over time—profoundly distort our understanding of tic epidemiology and prognosis. He’ll go over his findings from population-based data, school observations, and the New Tics prospective cohort, presenting what a less biased picture looks like. The perceived prevalence of Tic Disorders affects research and clinical decisions, making this kind of research vital.
This presentation by Dr. Black mirrors his keynote lecture from the European Society for the Study of Tourette Syndrome (ESSTS) annual meeting, “If a tree tics in the forest and no one is around to hear it, does it have a tic disorder? Selection bias and the natural history of tics.”
About the Tics + Topics Research Series
Key Takeaways
- Tic Disorders are far more common than we think. Roughly half of children show observable tics during elementary school, and at least a quarter likely meet criteria for a Chronic Tic Disorder, much higher rates than clinic-based samples suggest.
- Most children with tics are not significantly impaired and never get diagnosed. Despite the high prevalence, only a minority experience clinically meaningful impairment or ever come to medical attention, meaning the cases we see in clinics represent a skewed, unrepresentative slice of the population.
- Bias at every level distorts our understanding of tics. Selection and ascertainment biases. Such as, from who gets noticed, to who sees a doctor, to who enrolls in research studies, systematically warp what we know about the epidemiology and prognosis of Tic Disorders, making the condition appear rarer and more severe than it is.
Kevin J. Black, MD
Dr. Black is a movement disorders neuropsychiatrist whose research and clinical care have focused on Tourette Syndrome (TS) and Provisional Tic Disorder (tics occurring less than a year after onset). His laboratory demonstrated both clinical and, for the first time, neuroimaging predictors of outcome at the most clinically relevant time point (one year after tics began). He has also contributed to single-site and multisite clinical trials of TS, and has written reviews and book chapters.
Publications from the New Tics study received widespread attention; his 2016 review of Provisional Tic Disorder was viewed over 150,000 times. He also contributed to the 2021 Tourette Association of America position paper on the phenomenon of social media-inspired functional tic-like behavior and to the 2021 Martino et al. consensus document defining treatment failure in TS. He serves as co-investigator for the ENIGMA-TS genetics and neuroimaging study, the largest brain imaging study to date in TS.
