The causes of this disorder, when it occurs in the absence of other conditions, are unknown. The movements appear to increase with stress, frustration, and boredom. Stereotypic movement disorder is more common among boys.
Stimulants (such as cocaine and amphetamines) can prompt a severe, but short (a few hours) period of stereotypical movement behavior, which 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 can also cause this disorder.
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