Definition of Stereotypic movement disorder:

Stereotypic movement disorder is a condition in which a person makes repetitive, purposeless movements (such as hand waving, body rocking, or head banging) for at least four weeks. The movements interfere with normal activity or have the potential to cause bodily harm.

Causes, incidence, and risk factors:

Stereotypic movement disorder is more common among boys than girls. The repetitive movements appear to increase with stress, frustration, and boredom.

The cause of this disorder, when it occurs in the absence of other conditions, is unknown.

Stimulants such as cocaine and amphetamines can prompt a severe, but short period of stereotypic movement behavior. The behavior may include repetitive and purposeless picking, hand wringing, head tics, or lip-biting. Long-term abuse of stimulants may lead to longer periods of stereotypic movement behavior.

Head injuries may also cause stereotypic movements.