Although both tics and stereotypies both involve repetitive, involuntary movements, stereotypies have an earlier age of onset (usually before age 3) and involve the whole body, whereas tics are commonly seen in the eyes, face or head. Tics are also associated with discomfort or stress, whereas stereotypies are self-stimulatory.
Individuals can engage in non-injurious or injurious stereotypic movements that are individually variable. Examples of non-self-injurious stereotypic movements include, but are not limited to, body rocking, bilateral flapping or rotating hand movements, flicking or fluttering fingers in front of the face, arm waving or flapping, and head nodding. Stereotyped self-injurious behaviors include repetitive head banging, face slapping, eye poking, and biting of hands, lips, or other body parts. Multiple movements may be combined (e.g., cocking the head, rocking the torso, waving a small string repetitively in front of the face). Stereotypic movements frequently seen in adults include skin picking and scratching, nail biting, lip biting and eye rubbing. The movements can last for more than one minute and can occur several times a day. The frequency and intensity of the behaviors are contingent upon environmental and internal factors. The most common triggers for stereotypic behaviors are excitement, happiness, boredom, anxiety, concentration on a task and fatigue.