The relationships between restrictive/repetitive behaviours, intolerance of uncertainty, and anxiety in autism: A systematic review and meta-analysis

Autistic people are more likely to experience anxiety than their non-autistic peers. Understanding mechanisms underpinning anxiety in autism is a vital aspect of developing effective interventions. Intolerance of uncertainty (IU) and restrictive/repetitive behaviours (RRBs) are proposed to contribute to anxiety for autistic people. This paper includes the first meta-analysis to investigate the associations between all three of these variables. A systematic search identified 33 papers that measured anxiety, IU and RRBs in 8347 autistic participants. Evidence was found for positive correlations between all three variables. Analysis of average participant age demonstrated that the relationship between anxiety and IU was stronger in younger participants. No significant differences were found between the associations in studies that included participants with intellectual disabilities and those that did not. A quality assessment framework identified methodological threats to validity. Most studies had good methods of recruitment; however, many anxiety and IU measurement tools were unvalidated in autistic populations. Results suggest that IU and RRBs should be considered when designing anxiety interventions for autistic people, however, the role of RRBs in particular needs to be investigated further to prevent interventions from taking away important coping strategies due to misunderstanding of causal relationships.