Background:

Autism research has relatively neglected restricted repetitive behaviors (RRB) and autistic adults compared with the social domain of autism and autistic children. With this review, we aimed to synthesize what is currently known about autistic adult’s self-reported RRB, researcher’s use of methods, and consideration of masking and gender, and to highlight gaps in our knowledge to inform future research.

Methods:

We conducted a systematic search of five databases that we last ran in February 2023. We included studies where autistic adults self-reported on one or more subtypes of their repetitive behaviors. We conducted a narrative synthesis to summarize results. We used the Mixed Methods Appraisal Tool to assess the quality of included studies.

Results:

Our database search identified 35 studies to include for review. The majority of included studies focused on the sensory domain of RRB with other subtypes comparatively neglected. The narrative synthesis identified subject areas of stimuli characteristics, internal reactions, moderators, recovery, self-regulation, and social pressure. We uncovered a narrative where most autistic adults experience hypersensitivity to some sensory stimuli, the unpleasantness of which they then try to avoid, but in doing so may also avoid social situations, contributing to loneliness and increased anxiety surrounding social situations. We identified a cycle of stress where existing stress increased sensory sensitivities leading to more stress and less ability to deal with additional stressors. While the self-regulatory benefits on emotion, cognition, and self-fulfillment of RRB should help with stress, this was prevented by autistic people’s awareness of stigma surrounding these behaviors, leading to masking, which is also stressful.

Conclusion:

The review highlighted the need for a less categorical and more interrelated approach in researching this domain of autism and a need for more awareness surrounding sensory issues and the benefits of RRB. Future research should also strive to improve study sample representation, particularly regarding gender, race, and IQ.

Community Brief Why is this an important topic?

Historically, research has focused on autistic children and social differences rather than on autistic adults and their repetitive behaviors such as repetitive movements, insisting on sameness, sensory sensitivities, and special or preferred interests. Research has often asked parents and carers about these behaviors rather than asking autistic adults. As such autistic adults’ own experiences of their repetitive behaviors are not well known in research.

What was the purpose of this review?

The purpose of this review was to find out: -

Which repetitive behaviors have already been studied in self-reporting autistic adults.

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How self-reporting autistic adults’ repetitive behaviors have been studied.

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What the findings of those studies were and to summarize them.

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If masking (the “hiding” of autistic behaviors) and gender differences have been considered in these studies.

What did the researchers do?

We conducted a systematic review looking at papers where autistic adults self-reported/participated in studies exploring one or more repetitive behaviors. A systematic review searches and summarizes all existing research on a topic to answer specific questions and make clear what we already know about a topic and what still needs to be researched. Our search ran until February 2023 and found 35 papers.

What were the results of the review?

We found that sensory sensitivities are researched more than other repetitive behaviors, followed by special interests. We also found that autistic adults’ repetitive behaviors are self-fulfilling and help them manage their emotions and attention. This helps them to cope with things that might cause stress, such as sensory sensitivities. Autistic people said that they had strong internal reactions to sensory stimuli, especially those such as loud or high-pitched noises, bright lights, scratchy textures, and strong smells. This was made worse where multiple of these things were present; multiple stimuli overlapped, they couldn’t control the sensory stimuli, were already stressed, and because of past or present negative reactions of others. Repetitive behaviors are often viewed negatively or stigmatized by others, and so many autistic adults mask or hide these behaviors. This may cause problems for autistic people—although very little research has looked into this. Gender differences were also not considered often. There was no gender difference in the amount or intensity of repetitive behaviors; females seemed to have increased sensitivity to taste and smell and had different special interests to males.

What are the next steps?

Future research should consider repetitive behaviors as a whole and how they relate to one another. Researchers should recruit participants to better represent autistic adults of all backgrounds, particularly regarding gender, race, and IQ, as current findings are fairly limited to white autistic adults of average or above average intelligence within the gender binary.

What are the potential weaknesses of the review?

The review looks at self-reporting autistic people; this means that the review does not look at autistic people who cannot self-report, and so the findings may not apply to them. It is also possible that we missed potentially relevant studies in our search, although every effort was made to avoid doing so. Some studies had to be excluded because results were reported in a way that did not separate the experiences of autistic adults from other groups such as children or adults with attention-deficit hyperactivity disorder (ADHD) who were not autistic. This increases the review’s relevancy to autistic adults but means that some potentially relevant findings were not reported.

How will these findings help autistic adults now or in the future?

The findings in this review help to highlight the areas of restricted repetitive behavior (RRB) research that are lacking, particularly regarding insistence on sameness behaviors and repetitive movements. This will hopefully prompt more research in these areas and increase understanding of these misunderstood behaviors. The findings also highlighted the experience of sensory sensitivities and the benefits of other forms of RRB, which challenges the stigma surrounding these behaviors and increases awareness.