(as defined by the American Academy of Pediatrics)
Tics are rapid, repetitive movements or vocal utterances. They may be motor (like excessive eye blinking) or vocal (such as a habitual cough or chronic repetitive throat clearing noises), chronic (continuing throughout childhood), or transient (lasting less than 1–2 years). In children who eventually develop tic disorders and ADHD, the ADHD usually develops 2 to 3 years before the tics.
Tics tend to resemble certain ADHD-related symptoms— fidgeting and making random noises in particular—and may occasionally are mistaken for signs of ADHD. True tics, however, differ from ADHD-type fidgetiness or hyperactivity in that they almost always involve rapid, repeated, identical movements of the face or shoulders or vocal sounds or phrases—they may cause a child to become socially isolated.
Tourette syndrome, which is quite rare, is a more severe form of tic disorder involving motor and vocal tics that occur many times per day. The average age at which it appears is 7 years. While children with Tourette syndrome may develop ADHD, the 2 disorders are separate and independent conditions. Attention-deficit/hyperactivity disorder is not a variant of Tourette syndrome, and Tourette syndrome is not just a variety of ADHD. Research has shown that chronic tic disorders, Tourette syndrome, and OCD may stem from some common factors, and a child with any of these conditions is quite likely to also have ADHD.
For more on this topic, please visit: Tic Disorders