Stereotypic Movement Disorder

The essential feature of Stereotypic Movement Disorder is motor behavior that is repetitive, often seemingly driven, and nonfunctional.

This motor behavior markedly interferes with normal activities or results in self-inflicted bodily injury that is significant enough to require medical treatment (or would result in such injury if protective measures were not used.

If Mental Retardation is present, the stereotypic or self-injurious behavior is sufficiently severe to become a focus of treatment . The behavior is not better accounted for by a compulsion (as in Obsessive-Compulsive Disorder), a tic (as in the Tic Disorders), a stereotypy that is part of a Pervasive Developmental Disorder, or hair pulling (as in Trichotillomania).

The behavior is also not due to the direct physiological effects of a substance or a general medical condition. The motor behaviors must persist for at least 4 weeks.

Prevalence

There is limited information on the prevalence of Stereotypic Movement Disorder. The estimates of prevalence of self-injurious behaviors in individuals with Mental Retardation vary from 2% and 3% in children and adolescents living in the community to approximately 25% in adults with severe or profound Mental Retardation living in institutions.

Course

Course There is no typical age at onset or pattern of onset for Stereotypic Movement Disorder. The onset may follow a stressful environmental event. In nonverbal individuals with Severe Mental Retardation, stereotypic movements may be triggered by a painful general medical condition (e.g., a middle ear infection leading to head banging). The stereotypic movements often peak in adolescence and then may gradually decline.

Diagnostic criteria summarized from:

American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders, fourth edition. Washington, DC: American Psychiatric Association.