Background: This study estimated the true prevalence of chronic motor and vocal tic disorders, and Tourette's syndrome in students as well as its comorbidity with attention deficit/hyperactivity disorder (ADHD).
Methods: A random clustered sample of elementary students was selected from schools in Tabriz, Iran. Students were screened by Conner's teacher rating scale for ADHD and a detailed history from parents and teachers for the presence of any type of tic was obtained. Next, a clinical interview based on the Kiddie Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version (K-SADS-PL), and an interview with parents lead to the definitive diagnosis.
Results: A total of 1658 children were evaluated. Vocal tic was observed in 3.2% (±SD = 0.02) students, and was more prevalent in boys. ADHD was diagnosed in 45.5% of these students. Motor tic was observed in 7.3% (±SD = 0.02) of students. Almost half (48.1%) of these students had ADHD. Tourette's syndrome was observed in 1.3% (±SD = 0.01), with a male/female ratio of 3.5:1.
Conclusion: This is the first study to provide the prevalence of chronic tics in elementary school students in Iran. ADHD is more common among students with chronic tics and Tourette's syndrome.