Repetitive behavior

Relevance to autism:

Repetitive movements and manipulation of objects are among the first signs of autism to emerge in toddlers^1,2. Scores on tests of repetitive behavior at 2 years of age best predict autism at age 9³.

New findings about the importance of restricted and repetitive behaviors underlie the proposed revisions to the diagnostic criteria for autism proposed for the forthcoming fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, DSM-5, scheduled for 2013.

In DSM-IV, an autism diagnosis does not require an individual to exhibit restricted and repetitive behaviors, but in DSM-5, these behaviors are one of two domains required for diagnosis of an autism spectrum disorder.

Background:

Although ‘insistence on sameness’ was one of the core signs of autism noted by pioneering researchers Leo Kanner and Hans Asperger, researchers throughout the 20th century tended to focus more on the social and communication deficits characteristic of the disorder.

Consequently, knowledge about the role of these behaviors is sparse. They are believed to relieve anxiety in individuals with autism. However, there is little data to support this view. New research suggests that in autism, the brain’s reward system may be over-activated by some types of repetitive behavior and focused interests, at the same time that the nucleus accumbens, striatum and other brain regions involved in the reward circuitry are under-activated by social stimuli^4,5.

Researchers have long associated repetitive motor movements such as hand-flapping with low cognitive function, and higher-order restricted behaviors, such as intense focus on a particular object or interest, with good language and cognitive abilities.

But this assumption too is being reevaluated as new research shows that repetitive motor movements are present in individuals across the autism spectrum. There is some evidence to suggest that males may be more prone to these behaviors than females, but as gender differences in autism and repetitive and restricted behaviors are both understudied, more research is needed to confirm this.

Many of these behaviors are difficult to measure, though researchers are working on automated systems to quantify repetitive motor movements.

There are few treatments for restricted and repetitive behaviors and interests. Advocates urge researchers to tread carefully when attempting to ameliorate these behaviors as they serve important functions for individuals with autism.