Tics and Tic‐like Phenomena—Old Questions on a Grand New Scale Invited Editorial on TikTok and Tics

Among the classes of hyperkinetic movement disorders, tics occupy a rather unusual space. Their phenomenology may be indistinguishable from that of voluntary actions, and, therefore, an analysis of movement patterns and behaviors that may be labeled as tics relies mostly on the contextual factors that drive their occurrence. This means that in order to reliably classify a single motor event, including phonations and vocalizations, as a tic, more information is necessary, such as its rate of occurrence and the contingencies associated with its presence. This is very different from other movement disorders, where the kinematics of the motor event clearly depart from physiologic movement patterns, and leads to a degree of imprecision in the diagnostic approach. Clinical experience and individual expertise traditionally minimize this imprecision, but at the same differ according to schools of thought and medical training. It may appear surprising to many, but discussions with non‐movement disorder neurologists, and colleagues from other disciplines such as (neuro)psychiatrists and pediatricians often highlight the differences in the perception and language used to define this single unit of observation that is a tic.

One way to minimize difficulties in phenomenological labeling has been to rely on those clinical features that are consistently present in a common syndromic presentation, as in Gilles de la Tourette syndrome. Although this approach is not unique to tics (for example the approach to dystonia and paroxysmal movement disorders has been in many ways similar), it has provided a clinical stronghold in their definition. As a consequence, knowledge on the movement disorder of tics stems mostly from clinical observations made based on primary tic disorders, such as Gilles de la Tourette syndrome. This allowed narrowing down the defining characteristics of tics to repetitive and brief movements or sounds that are largely preceded by sensory antecedents (known as premonitory urges) and are most often temporarily suppressible with cognitive effort. However, the flipside of this approach was to merge phenomenology with etiology, thereby adding more layers of complexity to an already difficult topic. Of note, repetitive motor phenomena with characteristics akin to tics are not unique to Gilles de la Tourette syndrome and are observed in a range of different conditions, including functional neurological syndromes and other, often neuropsychiatric, disorders. ¹ , ² , ³

Recently, perhaps exacerbated by the COVID‐19 pandemic, a surge of mostly adolescents with repetitive movements or sounds, many of which would fall under the tic rubric, presented in clinics worldwide. ⁴ , ⁵ , ⁶ , ⁷ The majority of these cases had surprisingly similar clinical characteristics, as also described by Hull et al. in Movement Disorders Clinical Practice. ⁵ For example, in most cases, there was a sudden and often explosive onset of repetitive behaviors constituting a wide range of mostly complex phenomena. Self‐injurious behaviors, as well as repetitive hitting and throwing objects were also commonly observed, as were coprolalic utterances, often expressed as context‐specific statements. Unusual triggers and phenomena incompatible with tics, as demonstrated in the videos provided by Hull et al. ⁵ were also noted. Intriguingly, despite the large geographic diversity of the reported cases, the clinical phenomenology was in many ways uniform, which prompted the search for common denominators in the lives of affected individuals. This led to the identification of exposure to specific content in different online media platforms, such as TikTok or YouTube, portraying the very same or akin behaviors shared under the tic and/or Tourette's label. In fact, the study by Olvera et al. also published in the Movement Disorders Clinical Practice journal specifically analyzed the phenomenology of video content provided from individuals with the highest popularity (mean number of followers/individual: 2.5 million; range, 143,500–12.7 million; mean number of views/video, 11.8 million; range, 282,000–44.2 million) which were labeled as either tics or Tourette's. ⁷ Their results demonstrate significant phenomenological overlap between the video content and the behaviors of the cases discussed above. In fact, first Olvera et al., ⁷ followed by others, suggested that this rapid worldwide increase of cases in adolescents could reflect an example of mass sociogenic illness mediated through the wide outreach of online platforms.

There are several important points to highlight here. In most cases, the etiological labeling of a functional neurological disorder has been applied. Indeed, as noted above functional neurological syndromes may be one of the many etiologies that could present with complex repetitive behaviors. This is something to consider when approaching such cases, specifically with regard to their pathophysiology, which may in turn guide therapeutic decisions. Another aspect also relates to the novelty of the observed phenomenon. This is not the first time in medical history that people present with repetitive behaviors, including tics and tic‐like phenomena due to functional and other etiologies (discussed in ⁸ ). A read of the chapter on “Tics and Hysteria” in Meige and Feindel's phenomenological classic “Tics and their Treatment” offers one clear example out of many. ⁹ However, it is the scale of the current phenomenon that is unprecedented. One wonders, therefore, whether this might just be one of many (neuropsychiatric) phenomena that may surge, where both supervised and random exposure to social media may play a critical role. In this regard it may be of paramount importance to engage in discussion and consult with our colleagues from the neighboring disciplines of psychiatry, psychology, sociology and anthropology just to name a few, and also those on the translational interface of the ever‐expanding technologies for behavior modification. This brings us also to the very last point, which is phenomenology; what are these movements? How and based on which criteria do we distinguish between tics, tic‐like behaviors and non‐tic repetitive phenomena? This matter may appear contrived to some of the experts who do feel that this distinction, including etiological labeling is very clear. However, for most of us, many cases remain challenging, specifically when overlapping phenomena are present. It appears we are back at square one. How do we define our unit of observation that is a tic? The time is now to address this.

Author Roles

1. Research project: A. Conception, B. Organization, C. Execution;

2. Statistical Analysis: A. Design, B. Execution, C. Review and Critique;

3. Manuscript Preparation: A. Writing of the first draft, B. Review and Critique;

C.G.: 1A, 3A

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The approval of an institutional review board and informed patient consent were not necessary for this work. The author has read the Journal's position on issues involved in ethical publication and affirms that this work is consistent with those guidelines.

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