Stereotypic movement disorder is characterized by repetitive, non-functional motor behavior that has lasted at least 4 weeks. Certain drugs sometimes cause this condition, but symptoms last for a shorter period of time or stop when the offending medication is discontinued.

The cause of this disorder, when it occurs in the absence of other conditions, is unknown. The repetitive movements appear to increase with stress, frustration, and boredom. Stereotypic movement disorder is more common among boys than girls.

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.

With chronic stimulant abuse, these periods may last longer, but they usually resolve with cessation of the drug use.

Tourette's syndrome and autism may also cause this disorder.

• Rocking
• Head-banging
• Self-biting
• Nail-biting
• Hitting own body
• Handshaking or waving
• Mouthing of objects

A clinical exam is usually sufficient to diagnose this disorder. Tourette's syndrome, stimulant abuse, autism, and other potential causes should be considered and appropriate tests conducted.