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Functional tic-like behavioursDissociative identity disorder

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Case study

When similar movements are not the same disorder

Reports of rapid-onset functional tic-like behaviours during the social-media era are the strongest current clinical illustration that apparently similar symptoms can arise through different mechanisms. They are not a theory of all youth mental health.

What we know

Multiple specialist centres described a 2020–2022 surge of atypical, often explosive tic-like behaviours, mostly in adolescent females, differing from classic Tourette phenomenology. Functional neurological symptoms are genuine, not feigned.

How we know it

Clinical series, phenomenological comparison, some content analyses of TikTok ‘tic’ videos. No randomized exposure study. No solid community incidence.

What else could explain it

Pandemic anxiety and deprivation; disrupted care; recognition/referral effects; co-occurring functional and neurodevelopmental tics; selection into tic content.

What we don't know yet

Causation; community prevalence; persistence; whether social media produced symptoms or supplied a model for symptoms that stress would have produced anyway.

Tourette syndrome versus functional tic-like behaviours

Tourette syndrome

  • Typical onset: childhood, often 5–7 years.
  • Sex ratio: more commonly identified in males.
  • Course: waxing and waning; rostrocaudal march often described; premonitory urges common.
  • Phenomenology: brief, variable tics; coprolalia uncommon.
  • Associates: ADHD, OCD frequently co-occur.

Functional tic-like behaviours

  • Typical onset: abrupt, often adolescence, sometimes overnight in descriptions.
  • Sex ratio: published waves predominantly female.
  • Course: rapid escalation to complex, disabling sequences.
  • Phenomenology: longer, more elaborate, highly variable, often suggestible; coprophenomena more prominent than in clinic Tourette.
  • Context: high reported exposure to tic content; high anxiety/pandemic stress in many series.

Social-media exposure evidence

Müller-Vahl et al. (2022), Pringsheim et al. (2021), Heyman, Liang and Hedderly (2021), Olvera et al. (2021) and Hull and Parnes (2021) collectively document (a) a clinical wave, (b) a mismatch with typical Tourette, and (c) a temporal and sometimes reported-exposure association with popular tic content. That is association plus phenomenology, not a closed causal demonstration.

Competing explanations

Treatment and meaning

In FND care, explanation, reduced accidental reinforcement, treatment of anxiety, and rehabilitation are ordinary tools. None of that requires telling a young person they were faking. Functional diagnosis is a mechanism claim, not a character judgement.

If this case is used as a master key for ADHD, autism, depression, or DID, it is being misused. Its value is narrower and greater: it shows how to compare phenotypes, list confounders, and refuse both denial of a clinical wave and conversion of that wave into a culture-war slogan.