Functional Tic Disorder: a Pandemic in a Pandemic

In December 2020, a 19-year-old woman presented to our movement disorders clinic with an abrupt and explosive onset of tic-like movements and vocalizations and no previous history of tics.¹ Her tic-like movements were severe, complex, and mainly involving the extremities. She did not have a premonitory urge and her movements were semi-suppressible. She had a complicated psychiatric history including a recent hospitalization for suicidal ideation. She was not following up with a psychiatrist and reported her anxiety and depression had been worsening during the COVID-19 pandemic. She also had significant social stressors including discord between her parents, a mother with chronic illness, and being a victim of bullying at school.

During the COVID-19 pandemic, neurology clinics have seen an influx of similar young women with an abrupt onset of tic-like movements (Table 1).^1-4 Among these reports, a case series described 6 women who presented to a neurology clinic between November 2020 and January 2021,² and a similar case that presented in November 2020.³ Like our patient, these teenaged women did not have a history of tic disorders. None were able to suppress their movements and the minority described a premonitory urge. All described episodes of explosive “tic attacks,” in which movements were even more severe than at their baseline. A history of anxiety and depression were also common. Another case series identified 20 individuals with explosive onset who were almost all women in their second decade of life, most of whom also had a diagnosis of depression or anxiety.⁴

Functional Tics vs Classic Tourette Syndrome

Many features distinguish the cases described above from classic Tourette syndrome. Historically, tic disorders with an explosive and abrupt onset represent only 5% of cases of Tourette syndrome.⁵ A typical neurology clinic may therefore see only a handful of these types of referrals in a year, whereas beginning in late 2020, many neurology clinics began seeing several of these cases each week.^3,4 That the overwhelming majority of these referrals were women in adolescence is also atypical. The onset of tics typically occurs at age 5.6 to 7.3 years,^6,7 and tics classically go into remission during adolescence.⁸ Additionally, Tourette syndrome has a male predominance of 4.3:1.^4,6,7 The phenomenology seen in the recent cases is also different, with greater severity and complexity of motor tics and more coprophenomena (ie, obscene words and gestures or socially inappropriate behaviors) than classically seen in Tourette syndrome.^1-4 Typically, tics are only disruptive to behavior in 12% to 29% of cases,⁹ and only 5.1% of persons with Tourette syndrome ever have to go to the hospital because of severe tics.¹⁰ This new wave of tic-like movements presenting during the COVID-19 pandemic, however, has been causing an extreme degree of disability among those affected.⁴

Considering these unique characteristics, the consensus among neurologists specializing in movement disorders is that most of these new cases represent functional movement disorder (FMD),^1-4 which is covered in more detail in the articles The Diagnosis of Functional Movement Disorder and Treatment of Functional Movement Disorder in this issue. These new cases share phenomenologic and demographic similarities with previously described functional tic disorder and differ from classic Tourette syndrome in similar ways. In comparison with Tourette syndrome, functional tics are less likely to occur in the head and instead tend to involve the extremities.⁷ Functional tics tend to be complex, severe, and insuppressible.⁷ The “tic attacks” seen in these new cases have also been previously described in people with functional tics.^3,11 Functional tics occur more often in women and usually present at a later age, extending into adulthood, compared with Tourette syndrome.^4,12

FMD incidence has increased by as much as 60.1% during the COVID-19 pandemic.¹³ Similar to the cases described in this new wave of functional tics, the increased incidence of FMD is overwhelmingly in female persons who commonly have comorbid psychiatric disorders, typically depression and anxiety. Pringsheim and colleagues compared 20 cases of what they termed “rapid-onset functional tic-like behaviors” to historical data from the Calgary Tic Disorders Clinical Registry and found that the proportion of referrals to their centers for these functional tic-like behaviors increased about tenfold (from 1%-5% to 20%-35%). During that time, all clinics in the registry reported a significant increase in referrals for these functional tic-like behaviors, even those clinics where the overall number of referrals was stable or decreased.

Diagnosis of Functional vs Nonfunctional Tics

Although there is consensus among movement disorder specialists that these new cases are consistent with functional tics, it is important to note the difficulty in deciphering functional vs nonfunctional tic disorder.¹⁴ There are many overlapping features between functional tics and tics of any etiology, including classic Tourette syndrome. Psychiatric comorbidities are common in both,^7,15 although the prevalence of specific psychiatric comorbidities differs between functional and nonfunctional tics. Anxiety has been the predominant comorbidity in the new wave of cases described (Table 1), whereas Tourette syndrome is more commonly associated with attention-deficit disorder and obsessive-compulsive disorder.¹⁵ Phenomenologically, there are similarities between the etiologies (Table 2). For example, both disorders typically present with behaviors that are distractible, suppressible, and suggestible. Behaviors that are classic for tics can be seen in functional and nonfunctional etiologies, including coprophenomena, echophenomena (ie, repeating what another says or does), and paliphenomena (ie, repeating themselves, perseveration), as well as motor and phonic tcs. It is likely that some of these new cases involve a nonfunctional tic disorder that was unrecognized prior to presentation during the COVID-19 pandemic.

Social Media Use & Abrupt Onset of Tic-like Movements

The pathophysiology behind these new cases of abrupt onset of tic-like movements has not yet been studied but is likely similar to that of FMD as a whole. This includes a combination of predisposing factors (ie, genetic) and states (ie, anxiety) that are then subject to environmental or personal triggers resulting in FMD (Figure).¹⁵ In these new cases, the COVID-19 pandemic seems to be a unique environmental trigger.^3,4

Increasing social media use has also emerged as another possible catalyst for the new wave of cases. The women described in the 6-case series all reported having watched videos on the social media platform, TikTok, before developing symptoms, and this has also been reported in other case reports and series.^3,13 TikTok is a phone application and website, where users can create, post, and search for short videos with keywords or the now ubiquitous hashtags (#).¹⁶ Tic- and Tourette syndrome-related content has recently exploded in popularity on this site, and in March 2021, videos with the keywords #tourette and #tic had over 5 billion views.¹⁷

Another study focused not on patient’s phenomenology but rather on the phenomenology of the tic-like movements and vocalizations among the most popular TikTok content creators (ie, so-called “influencers”) who were known for their “tic” content.¹⁷ The 28 most popular videos of these creators had over 300 million views, on the TikTok platform alone, signifying the popularity of each of these videos. The influencers who created these videos are strikingly similar to individuals with tics described in this new wave of functional tic disorder presenting to neurology clinics (Table 1). Creators and their “tics” were also homogenous among the creators, who are mostly female persons, average age 19 years. The majority endorse a coexisting psychiatric disorder (eg, depression, anxiety or bipolar disorder). Their tic-like movements are severe and frequent in videos, and their average tic rate was 29/ minute compared with the 0 to 13/minute seen in Tourette syndrome.⁶ Coprolalia or copropraxia was present in 93%, and more than 85% had severe self-injurious behavior similar to that in the described cases, which typically occur in only a minority of Tourette syndrome cases.⁶

Because of the similarities between those presenting to neurology clinics with rapid-onset explosive, and presumably, functional tics and the TikTok influencers described the phrase “TikTok tics” has emerged and been covered in the global mainstream media.¹⁸ It is likely that this is, in part, related to the interest in social media in general, given its exponential growth over the past decade and especially during the COVID-19 pandemic.¹⁹ Much of the media coverage has alluded to a direct and causative relationship between watching TikTok and developing these more severe functional tics (ie, if you watch “TikTok tics,” you may “catch” tics yourself.) The relationship between social media use and these new tic cases, however, is complex and very unlikely to be simple causation. Patients with an abrupt onset of tic-like movements have reported that social media use may lead to “peer support, recognition and a sense of belonging”; however, “this attention and support may be inadvertently reinforcing and maintaining symptoms.”³ For example, in people with underlying Tourette syndrome, watching videos of tics may lead to echopraxia or echolalia, in which they mimic the movements or vocalizations of others. Therefore, although social media use may be acting as an almost global support group for patients with tics, it may also worsen tic severity or bring out injurious tic phenomena. The COVID-19 pandemic, similarly, has been an obvious source of emotional, physical, and financial stress across the globe, social media use itself may also be a stressor that could trigger these movements. Social media use has been tied to worsening anxiety, psychologic distress, and worsened sense of well-being.^20,21 In the case of “TikTok tic” influencers, financial gain also is also a consideration for etiology because the majority of these content creators sell merchandise via these videos or were paid for appearances.¹⁷ Influencers with the most popular videos, which tended to be those featuring more frequent and severe tics,¹⁷ would likely gain more followers and perhaps thereby increase their income.

Mass Sociogenic Illness

Mass sociogenic illness (also called mass hysteria) is defined as a “rapid spread of illness signs and symptoms affecting members of a cohesive group, originating from a nervous system disturbance involving excitation, loss or alteration of function, whereby physical complaints that are exhibited unconsciously have no corresponding organic etiology.”²² Tic-like movements have spread through social communities as part of mass sociogenic illness several times in the past. In Le Roy, NY in October 2011, 20 teenagers, primarily female persons, developed similar tic-like movements over the span of a month.²³ Famously, the Salem Witch Trials in the spring of 1692 is also theorized to possibly represent a similar phenomenon.²⁴ Mass sociogenic illness is generally a poorly understood phenomenon, partly because it is difficult to study these relatively infrequent occurrences that come and go during very discrete time intervals, often lasting only weeks or months. Today’s “TikTok tics” likely represent another of these unique moments. Individuals linked by TikTok during a global pandemic have developed strikingly similar movement disorders, suggesting that this is the first instance of mass sociogenic illness transmitted via social media rather than traditional social networks.²⁵ This interpretation is supported by reports of these behaviors from around the world, making this phenomenon a “pandemic.” For example, the “TikTok tic” vocalization of the word “beans” was present in the majority of the most popular content creators from around the world. This specific vocalization was also heard from the patients described from our movement disorders clinic.

Prognosis and Treatment of Abrupt Onset of Tic-like Movements

Anecdotally, cases of women in their teens with an abrupt onset of tic-like movements presenting to our movement disorders clinic recently have declined, and those previously affected have had improvement in their tic episodes. The patient described in the case above had improved significantly at follow-up 4 months later, after treatment with guanfacine (a mild medication used for tics) and regular psychiatric care. She now has only mild, intermittent tics that are no longer disruptive to her daily activities.¹ In previous mass sociogenic illness events, the abnormal movements and symptoms resolved within a span of months.^23,24 The natural history of these new cases, thus, may be self-resolving, although for some, tic-like movements may follow the course of functional neurologic symptom disorder and become a chronic condition. Additionally, the psychiatric comorbidities that have been extremely common among these new cases are unlikely to self-resolve without ongoing care, and psychiatric treatment is required. Even in individuals with underlying tic disorders, tics may improve with psychiatric management alone. Both functional tic disorder and psychiatric conditions may respond to cognitive behavioral therapy (CBT) and in the case of tic disorders, comprehensive behavioral intervention (CBIT), which shares many characteristics with CBT, can be helpful. Finally, medication regimens that treat both illnesses are a possibility, although care should be taken because of the risk of adverse effects with the long-term use of neuroleptic medications.