Stereotypy refers to repetitive, invariant behavior patterns with no obvious goal or function. Stereotypies are common in a variety of neurodevelopmental disorders, including autism spectrum disorder, intellectual disability, and fragile X syndrome. Some examples of stereotypy include hand flapping, body rocking, repeating words or phrases, and repeatedly lining up toys. Stereotypies can interfere with learning and social interaction, so understanding these behaviors is important. In this article, we will provide an overview of stereotypy, looking at what defines it, what causes it, who it affects, and how it is treated.
What defines stereotypy behavior?
Stereotypies are defined by several key features:
- Repetitive – The behavior is repeated over and over in a similar manner.
- Invariant – Each time the behavior occurs, it is carried out the same way with little variation.
- Seemingly purposeless – The behavior does not appear to serve an obvious goal or function.
- Ritualistic – Stereotypies often have a ritualistic, “just right” quality.
- Automatic – The person may perform the behavior somewhat unconsciously without trying.
Stereotypies are distinguished from other repetitive behaviors like tics, compulsions, and self-stimulatory behavior based on these defining features. They are not goal-directed like compulsions, not suppressible like tics, and do not provide generalized sensory stimulation like self-stimulation.
What causes stereotypy?
The exact causes of stereotypy are still unclear, but research points to abnormalities in the basal ganglia region of the brain. The basal ganglia help regulate and inhibit motor movements and behaviors. Dysfunction in these neural circuits may allow repetitive behaviors like stereotypies to persist unchecked.
Genetic conditions like fragile X syndrome directly impact basal ganglia development. Environmental factors like sensory deprivation or social isolation may also play a role by depriving the brain of needed input and stimulation during key developmental periods.
Role of the basal ganglia
The basal ganglia are a group of structures deep in the brain involved in controlling voluntary motor movements and behaviors. One of their main functions is to inhibit unnecessary or competing motor patterns, allowing wanted behaviors to proceed smoothly.
Studies of individuals with stereotypy show reduced volume and cell density in basal ganglia structures like the caudate nucleus and putamen. Abnormalities in the neurotransmitters dopamine and GABA have also been found. This suggests impaired functioning in the very regions and systems that normally inhibit repetitive, functionless behaviors.
Genetic syndromes
Many genetic syndromes involve stereotypy as a common symptom. Fragile X syndrome,Angelman syndrome, Prader-Willi syndrome, and Rett syndrome all have high rates ofstereotypy. These conditions involve mutations or abnormalities in genes important for brain development.
For example, Fragile X syndrome is caused by a mutation affecting production of the FMRP protein, which regulates synapses. Loss of this protein disrupts brain circuits during development. The basal ganglia are especially impacted, setting the stage for later emergence of stereotypy.
Environmental influences
While genetics play a clear role, research also suggests environmental factors can contribute to stereotypy. Social isolation, sensory deprivation, stress, and lack of stimulation are all proposed risk factors, especially early in development.
In animal studies, isolation rearing of young rats leads to higher rates of motor stereotypies. This implies a need for varied, enriched input during critical learning periods. When key brain regions do not receive needed stimulation, normal circuit wiring may fail to occur.
Who is affected by stereotypy?
Autism spectrum disorder
Stereotypy is very common in autism spectrum disorder, occurring in over 90% of individuals. Hand flapping, body rocking, spinning, and repeating words or phrases are some frequently seen stereotypies. These behaviors typically first appear around ages 2-4 during key stages of language and cognitive development.
Intellectual disability
Stereotypies are seen in around 30-60% of those with intellectual disability. Repetitive self-injurious behaviors like head hitting are more common in this group compared to those with autism. More severe intellectual impairment is associated with higher stereotypy rates.
Fragile X syndrome
Nearly 90% of males and over 60% of females with fragile X syndrome display stereotypies. Hand biting, hand flapping, and repetitive speech are most common. These behaviors may worsen during periods of stress or excitement.
Prader-Willi syndrome
About 60-80% of individuals with Prader-Willi syndrome exhibit stereotypy behaviors. Skin picking, hand flapping, and lining up objects are frequently reported. Rates are higher in those with greater cognitive impairment.
Angelman syndrome
Over 80% of children with Angelman syndrome show stereotyped behaviors. Hand flapping, mouthing of objects, and flipping pages repetitively are commonly seen. Stereotypies typically persist and do not diminish with age in this group.
Rett syndrome
Stereotypies like hand wringing, hand mouthing, body rocking and hand clapping are core diagnostic features of Rett syndrome, occurring in nearly all individuals. These behaviors may lessen after ages 5-8 but often reemerge during adolescence.
How are stereotypies treated?
Several treatment approaches may help reduce stereotypy behavior:
Behavioral interventions
Applied behavior analysis uses reinforcement and redirection to decrease stereotypy and teach replacement skills. Functional communication training can teach appropriate ways to communicate wants and needs. Rewarding desired behaviors while withholding reinforcement for stereotypy can be effective.
Antipsychotics
Medications like risperidone, aripiprazole and olanzapine may reduce stereotypy, but side effects like weight gain and sedation can occur. Data on long-term efficacy is limited.
Cognitive behavioral therapy (CBT)
CBT aims to improve cognitive control and awareness of behaviors. Strategies include self-monitoring, modifying antecedents, and providing alternative activities. CBT requires cognitive skills, so is more suitable for higher-functioning individuals.
Enriched environments
Enriched home and classroom settings with greater structure, sensory-motor stimulation, and opportunities for engagement may prevent or interrupt repetitive behaviors. Customizing activities to individual interests is most effective.
Alternative therapies
Massage, acupuncture, music therapy and animal therapy show initial promise in small studies. These may act by enhancing relaxation, sensory stimulation and social engagement. More research on longevity of effects is needed.
Conclusion
Stereotypy encompasses a range of repetitive, invariant motor and vocal behaviors commonly seen in neurodevelopmental disorders. Dysfunction in the basal ganglia and genetic mutations disrupt normal inhibition of unnecessary movements. While sometimes serving a self-regulatory function, stereotypies can interfere with learning and socialization. Behavioral and environmental modifications are first-line treatments, with medications used judiciously due to side effects. Further research on behavioral neuroscience and long-term treatments will enhance outcomes for this complex group of disorders. Understanding the origins and functions of stereotypies in individual cases is key for making progress.