Background Autism spectrum disorder (ASD) is a neurodevelopmental disorder defined by persistent deficits in social functioning and the presence of restricted and repetitive behaviours (RRBs). RRBs refer to four subtypes of behaviour including repetitive movements, speech, or use of objects; insistence on sameness; restricted interests; and sensory processing abnormalities. Many individuals with ASD also experience anxiety, which compounds ASD-related difficulties and inhibits daily functioning. RRBs have been found to be positively associated with anxiety; however, our understanding of the interplay between RRB subtypes and anxiety remains unclear. Thus, the current review aims to clarify the association between RRBs and anxiety by conducting a systematic review and meta-analysis. Methods To identify relevant studies, we will search five databases: CINAHL Plus, Cochrane Central Register of Controlled Trials, Ovid MEDLINE, PsycINFO, and Scopus. Articles included in the review will have their titles, abstracts, and full texts reviewed by two independent authors and their methodological quality assessed via the modified Newcastle-Ottawa Scale. Random-effects meta-analyses will then be conducted to calculate the pooled association between RRB subtypes and anxiety. Sensitivity analyses will also be conducted to assess the potential impact of bias, missing data, outliers, and methodological differences on this relationship. Additionally, this review will collate the factors which may influence the anxiety-RRB relationship to help identify who is most vulnerable to developing anxiety. Discussion This will be the first review to examine the association between the four subtypes of RRBs and anxiety in individuals with ASD. Understanding this relationship, and the factors associated with this, may help clinicians understand the different underpinnings and presentations of anxiety within this population with potential implications for assessment and treatment. Systematic review registration PROSPERO CRD42020185434

BackgroundAutism Spectrum Disorder (ASD) is a neurodevelopmental disorder defined by persistent deficits in social functioning and the presence of restricted and repetitive behaviours (RRBs). RRBs refer to four subtypes of behaviour including repetitive movements, speech or use of objects; insistence on sameness; restricted interests; and sensory processing abnormalities. Many individuals with ASD also experience anxiety, which compounds ASD related difficulties and inhibits daily functioning. RRBs have been found to be positively associated with anxiety, however our understanding of the interplay between RRB subtypes and anxiety remains unclear. Thus, the current review aims to systematically review and meta-analyse the association between RRBs and anxiety. Methods This review will collate studies which analyse the association between RRBs and anxiety in individuals with ASD. We will search five databases: CINAHL Plus, Cochrane Central Register of Controlled Trials, Ovid MEDLINE, PsycINFO, and Scopus. Articles included in the review will have their titles, abstracts and full texts reviewed by two independent authors and their risk of bias assessed via the modified Newcastle-Ottawa Scale. DiscussionThis will be the first review to examine the association between anxiety and the four subtypes of RRBs in individuals with ASD. Understanding this relationship, and the factors associated with this, may help clinicians understand the different underpinnings and presentations of anxiety within this population with potential implications for assessment and treatment.Systematic Review Registration PROSPERO CRD42020185434