Do adolescents with severe autism spectrum disorder develop motor and vocal tics?

Tics in Adolescents with Severe Autism Spectrum Disorder

Yes, adolescents with severe ASD commonly develop tics, with reported rates ranging from 18-67% depending on assessment methods, and these tics are clinically indistinguishable from those seen in primary tic disorders. 1, 2

Prevalence and Clinical Significance

The occurrence of tics in ASD is substantially higher than in the general population and should not be overlooked:

• In clinical samples of children and adolescents with ASD, 22% present with tic disorders: 11% meet criteria for Tourette disorder and 11% have chronic motor tics 1
• Video-based expert review reveals even higher rates: 67% of patients with severe ASD and stereotypies showed possible comorbid tics when recordings were systematically analyzed by movement disorder specialists 2
• Recent large-scale studies confirm: 18.4% of individuals with ASD (ages 4-18 years) demonstrate tic symptoms when assessed with standardized instruments 3

Relationship Between ASD Severity and Tic Occurrence

Higher cognitive functioning paradoxically correlates with increased tic prevalence in ASD:

• The proportion of tic symptoms is significantly higher among individuals with ASD who have IQ scores ≥70 3
• An association exists between the level of mental retardation and tic severity, with various degrees of cognitive impairment present in all individuals with comorbid ASD and tics 1
• Individuals with ASD and tics have significantly higher full-scale IQ scores compared to those with ASD alone 3

Characteristic Tic Presentations in ASD

The most frequently observed tics in adolescents with severe ASD include:

• Motor tics: Eye blinking, shoulder shrugging, neck bending, and staring 2
• Vocal tics: Throat clearing, sniffing, grunting, coughing, squeaking, and barking 4, 5
• Distribution pattern: Both motor and vocal tics commonly co-occur (40% of those with tics) 3
• Severity: Mean Modified Rush Videotape Rating Scale score of 5, indicating mild tic severity in most cases 2

Critical Diagnostic Considerations

Tics in ASD are frequently misdiagnosed as stereotypies, leading to inappropriate management:

• Tics in ASD are phenomenologically indistinguishable from tics in Gilles de la Tourette syndrome, with similar distribution patterns but generally less severe presentation 6
• The differential diagnosis between stereotypies and tics can be difficult in severe ASD but is clinically relevant due to treatment implications 2
• Key distinguishing feature: Tic awareness is markedly limited in ASD—only 50% of adults with ASD and tics are aware of their tics, compared to 100% awareness in primary Tourette syndrome 6

Associated Clinical Features

Adolescents with ASD and comorbid tics demonstrate more severe overall symptomatology:

• Significantly higher scores on Social Responsiveness Scale-2, Child Behavior Checklists, and Yale-Brown Obsessive-Compulsive Scale compared to ASD without tics 3
• The severity of core and comorbid ASD symptoms correlates positively with both the occurrence and severity of tic disorders 3
• Interestingly, patients without tics have a higher total number of stereotypies (p=0.01), suggesting possible diagnostic overlap or misclassification 2

Common Diagnostic Pitfalls to Avoid

The American Academy of Neurology and American College of Chest Physicians warn against several critical errors:

• Avoid misdiagnosing tics as "habit behaviors" or "psychogenic symptoms," which leads to inappropriate interventions and treatment delays 4, 5
• Do not use outdated terminology like "habit cough" or "psychogenic cough"—use "tic cough" to align with DSM-5 classification 5
• Avoid performing excessive medical testing, as tic diagnosis is primarily clinical and unnecessary testing causes iatrogenic harm 4
• Do not assume tics cannot occur during sleep—cough tics can persist during sleep in Tourette syndrome, contradicting outdated teaching 7

Clinical Assessment Approach

When evaluating repetitive behaviors in adolescents with severe ASD:

• Systematically assess for suppressibility and premonitory sensations, though these features may be difficult to elicit in severe ASD due to limited tic awareness 4, 6
• Look for the characteristic waxing-waning pattern that fluctuates over weeks to months 4, 5
• Note whether behaviors diminish when attention is diverted elsewhere and can be modified by suggestion 5
• Screen for common comorbidities: ADHD (present in 50-75% of Tourette syndrome cases) and obsessive-compulsive behaviors (30-60% of cases) 4

Prognosis Considerations

Natural history differs between primary tic disorders and ASD-associated tics:

• In primary Tourette syndrome, nearly half of patients experience spontaneous remission by age 18, with less than 20% continuing to have clinically impairing tics as adults 4
• The long-term trajectory of tics specifically in severe ASD populations requires further longitudinal study, as current evidence focuses primarily on cross-sectional assessments 1, 2, 3