Stereotypic movement disorder is characterized by repetitive, seemingly driven, nonfunctional movements including hand-waving, head-banging, body-rocking, fiddling with fingers, self-biting, or hitting various parts of one’s own body. These behaviors can be problematic for a number of reasons because they may result in self-injury, affect general health, result in significant social stigmatization, interfere with acquisition of new skills, and interfere with performance of existing skills.

20.2.1 Diagnostic Features

Stereotypies are repetitive, driven, and nonfunctional motor behavior. They are voluntary, lack variability, persist over time, are immutable even when the environment changes, and are inconsistent with the person’s expected development. Stereotypic movements are problematic when they interfere with a person’s overall functioning, become socially stigmatizing, or result in self-injury.

20.2.2 Epidemiology

Stereotypic movements are relatively common. For example, as many as 90% of typically developing children engage in body-rocking as a normal part of motor development, and 10% of normally developing 2-year-olds engage in head-banging while having tantrums.

Stereotypic movements are present but rare in populations of adults with average intelligence. These behaviors are predictably longer-lived and more impairing in developmentally delayed populations. In fact, the more severe the level of retardation, the more likely the person is to exhibit stereotypic movements, and the more likely these will be self-injurious.

20.2.3 Comorbidity

Stereotypic movement disorder occurs most frequently in people with mental retardation, or pervasive developmental disorders. Because they are both related to conditions of neglect, stereotypic movement disorder may co-occur with RAD. Several other conditions are also associated with stereotypic movements. Some genetic syndromes associated with it are Lesh–Nyhan syndrome (self-biting of the forearms), Prader–Willi syndrome (picking skin of the back of the hands), and Fragile X syndrome.

20.2.4 Differential Diagnosis

The stereotypic behaviors must be distinguished from a variety of other movements. Like most other DSM-IV-TR diagnoses, the behaviors must be severe enough to cause impairment in functioning. Stereotypic movement disorder is often diagnosed in people with mental retardation. However, stereotypic movements are considered a feature of pervasive developmental disorders and therefore would not be given a separate diagnosis when they occur in such individuals.

Stereotypic movement disorder must also be distinguished from a variety of different behaviors. For example, compulsions associated with obsessive–compulsive disorder (see Chapter 15) can look like stereotypic movements. Likewise, movements from the effects of certain medications, such as the antipsychotic group, should be taken into consideration and ruled out.

Developmentally appropriate self-stimulatory behaviors such as thumb-sucking can be differentiated by the appropriateness of the behavior to the child’s developmental level, changes in the behavior in response to the environment, and extinction of the behavior as the child develops.

Trichotillomania is another condition that must be distinguished from stereotypic movement disorder. Factitious disorder with predominantly physical signs and symptoms, and self-mutilation associated with personality disorders, mood disorders, and psychotic disorders, should also be differentiated from stereotypic movement disorder.

20.2.5 Etiology

Stereotypic movement disorder has a multifactorial pathophysiology involving a complex interaction between several neurological pathways, psychological factors, and social factors. Considerable research had addressed the neurobiology of stereotypies. Dopaminergic, serotinergic, and endogenous opioid systems have been associated with stereotypic movements and self-injurious behavior.

Though little is known about the genetic factors affecting stereotypic movements, several genetic syndromes do predispose people to stereotypic movements and self-injurious behavior. These syndromes have unique mechanisms likely resulting in changes in the dopaminergic neurons and other changes leading to stereotypic movements.

Stereotypic movements may be understood as a form of operant behavior that is maintained and reinforced by consequences of the behavior. In addition, other factors may contribute to the timing and intensity of the behavior. For example, the behavior will be decreased in the presence of social stimulation. Stereotyped behavior is also decreased following strenuous exercise, although not following mild exercise.

Stereotypic and self-injurious behaviors may develop and persist in the absence of stimulation. Functional analysis of stereotypic behavior shows it can be maintained by positive reinforcement (e.g., sensory stimulation), negative reinforcement (e.g., removal of an unpleasant physical stimulus), or some combination of social and nonsocial reinforcement (e.g., social positive and automatic reinforcement).

Deprivation is the environmental factor most associated with stereotypic behavior. The self-stimulating effect of stereotypies has long been proposed as its function, thus explaining the increased prevalence of stereotypies in individuals living in institutions.

20.2.6 Treatments

Treatments include several classes of medication, as well as behavior plans and social interventions. In approaching treatment, the first step should be addressing the patient’s deprivation with social interventions, if possible. Behavioral treatments and medications can be used secondarily as needed for management of the patient’s symptoms.

No medications have been approved by the US Food and Drug Administration. However, several classes of medication have shown some efficacy in treatment of this disorder. Serotonin-reuptake inhibitors have shown some efficacy.

Antipsychotics are some of the most commonly prescribed drugs for people with mental retardation and behavioral problems. Studies and even case reports for stereotypic movements and self-injurious behaviors are sparse over the past decade, and previous studies were often seriously methodologically flawed. Despite widespread use of antipsychotics to treat stereotypies, they have limited evidence of efficacy and significant side-effects, and some scholars have suggested their use may not be appropriate. A few recent studies, however, have provided modest support for their use. In the autism literature, there are some studies that show improvement in stereotypic and self-injurious behavior with risperidone.

One study of valproic acid in the treatment of stereotypic behavior in autistic children showed a significant reduction in the stereotypic behavior in 13 patients as measured by the Children’s Yale–Brown Obsessive Compulsive Scale (C-YBOCS). Opioid receptor blockers have also been used for the treatment of self-injurious behavior with some efficacy.