Tics occur three to four times as often in boys as girls.
Tics may affect as many as one-fourth of all children at some time. These tics often involve the eyes or facial muscles. The most commonly seen facial tics are repetitive eye blinking, squinting, wrinkling of the nose, and twitches around the mouth. Repetitive throat clearing or deep throaty sounds or grunts may also be considered tics. Certain medications such as methylphenidate, used to treat hyperactivity in children, may precipitate tics in children already prone to the disorder or may worsen existing tics.