Understanding Restricted, Repetitive and Stereotyped Patterns of behavior in Autistic Disorder

Restricted, repetitive and stereotyped patterns of behavior are diagnostic symptom domains of autism spectrum disorder (ASD). Restricted and repetitive behaviors occur in most people with most forms of autism spectrum disorder. However not everyone with a diagnosis of an autism spectrum disorder will have the same restricted and repetitive behaviors. Stereotypical behaviors are not specific to autism and are associated with other disorders such as Tourette's syndrome, schizophrenia and mental retardation (Stoppelbein, et al. 2005; Kraepelin, 1899).

Repetitive stereotyped behaviors have been problematic to define due to the variation in the topography of type of movements. Repetitive stereotyped behaviors have been associated with tremor (more or less regular, rhythmic contracting of muscles and their antagonists.) There are various types of tremors: a) tics (sudden, brief, recurrent, inappropriate, and other irresistible movements, simple or complex, without purpose or aim), b) tardive dyskinesia (involuntary movements of the lips, jaws, and tongue), perseveration (repetition of recent movements, action, or speech in spite of the individual’s effort to produce a new movement), c) stereotypy (an action or group of actions or words monotonously repeated or a posture maintained abnormally long), d) mannerism (a normal goal-directed behavior which is performed in a peculiar stylized and idiosyncratic manner) and e) obsessional phenomena (repetitive, purposeless voluntary phenomena which the subject feels compelled to carry out, but does so under the influence of his or her own will) (Frith and Done, 1997). Baker (1992) divided repetitive stereotyped behaviors in two categories: 1) As consequence of a restricted environment and 2) repetitive stereotyped behaviors triggered by the central nervous system. According to Garner (2005) and Turner (1997), repetitive stereotyped behaviors can be defined as behaviors that are inappropriate, repetitive and unvarying in either goal or motor pattern. Repetitive stereotyped behaviors may be subdivided into two basic categories based on the unvarying manner in which the behaviors are repeated: (1) Stereotypies involve the unvarying inappropriate repetition of a particular set of movements and/or body postures that lack any goal or function. (2) Impulsive/compulsive behaviors involve the repetition of an inappropriate goal with variable flexible goal-directed behavior (Garner 2005). Cuccaro and colleagues (2004, 2007) identified two factors in the repetitive stereotyped behaviors: Factor 1) Repetitive sensory motor actions and Factor 2) Resistance to change. Esbensen and colleagues (2008) found that repetitive behaviors are a heterogeneous group of behaviors, with the subtypes of repetitive stereotyped behaviors having their own individual patterns across the lifespan. Stereotyped patterns of behavior include not only excessive atypical movement but also the loss of typical movement (e.g., catatonia) in this broader definition (Stoppelbein, et al. 2005; Heffernan, et al., 2003).

Motor stereotyped behaviors are apparently purposeless ranging from simple movements, such as flapping arms or hands, flipping fingers in front of eyes, making repetitive sounds such as "eeeee" or "dika dika dika", jumping up and down , clenching muscles or turning in circles, clapping and finger tapping, to more complex whole-body movements. Self-injurious behaviors (SIB) seem to be a form of restricted stereotypical behaviors (RSB) and share some similarities with symptoms of Obsessive-Compulsive Disorder (OCD) such as preoccupations, rituals, distress over changes in environment or routine and an insistence on sameness. Although restricted stereotypical behaviors have some comorbilities with OCD, however, OCD is not the same as the restricted and repetitive behaviors seen in many individuals with autism spectrum disorder. In a comparison on a range of repetitive behaviors between individuals with autism and individuals with obsessive-compulsive disorder (OCD), individuals with OCD reported more compulsive and obsessive behaviors than individuals with autism spectrum disorder and both groups reported more compulsions and obsessions than a typically developing comparison group (Zandt et al. 2007). However, autistic individuals are more likely to engage in repetitive ordering, hoarding, telling or asking, touching, tapping or rubbing, and self-injurious behaviors (SIB).

According to Turner (1997, 1999) restricted stereotyped behaviors in autism can be divided into “lower-level” behaviors characterized by repetitive movement, and “higher-level'” behaviors characterized by preoccupations, insistence on sameness, and restricted patterns of interest. According to Turner (1997, 1999, Moy, et al., 2008) “higher-level” repetitive stereotypical behaviors (RSB) are more specific to autism than “lower-level”. Abramson and colleagues (2005) found that repetitive stereotyped behaviors in autism may be on a spectrum with obsessive-compulsive traits, which may allow genetic researchers to identify different phenotypes groups in the autism spectrum disorder.

Although self-injurious behavior is not specific for autism spectrum disorder, it constitutes one of the most challenge forms of “lower-level” repetitive stereotyped behaviors.

There are several hypotheses about self-injurious behaviors as a repetitive stereotyped behavior. One leading theory explains repetitive stereotyped behaviors as an attempt to adjust arousal levels to maintain homeostasis by producing needed sensory stimulation or avoiding over-stimulating situations (Frith and Done, 1997). Applied behavior analysis (ABA) proposes that repetitive stereotyped behaviors may play a role in modulating the frequency and severity of the behaviors. Social theories suggest that repetitive stereotyped behaviors are coping strategies designed to decrease anxiety caused by social impairments. According to Hughes (2001) executive dysfunction such as deficits in cognitive flexibility, working memory, and response inhibition have been positively associated with repetitive stereotyped behaviors. Some neurobiological hypotheses have implicated various brain regions such as the caudate, cerebellar vermis, and frontal lobes as well as serotonin, opiod and dopamine systems play a significant role in repetitive and stereotyped behaviors (Stoppelbein, et al. 2005). For instance, short-term dietary depletion of the 5-hydroxytryptamine (5-HT) precursor tryptophan has been associated with an exacerbation of behavioral symptoms in autistic adults. In addition, genetic studies have associated the repetitive stereotypical behaviors with specific chromosomal regions.

MRI studies have demonstrated an increase in the volumes of the right caudate both OCD patients and autistic individuals [caudate nuclei: specific areas of the basal ganglia which are broadly responsible for body movement, sensorimotor coordination, including response selection and initiation (Grahn, et al., 2008)] Enlargement of the right caudate and total putamen has been positively associated with repetitive stereotyped behaviors in autistic adults (Hollander, et al. 2005) The corpus striatum has also been implicated in the pathophysiology of obsessive-compulsive disorder (OCD). Turner and colleagues (2006) using functional connectivity Magnetic Resonance Imaging (fcMRI) to examine functional neural networks incorporating the caudate nuclei found that in part atypically enhanced functional connectivity between caudate nuclei and other brain regions in autistic individuals may indicate more diffusely organized fiber tracts, possibly due to reduced synaptic pruning.