Sensory Hypersensitivity and the Predictability of Repetitive Behaviours in Autism Spectrum Disorder

Background: Repetitive behaviours (RBs) are a core diagnostic symptom of Autism Spectrum Disorder (ASD) and tremendously impact individuals' day-to-day lives, yet the underlying factors of RBs are not fully understood. Recent work suggests that sensory issues related to ASD, specifically sensory sensitivities, contribute to RBs. While these studies have provided evidence for a relationship between RBs and hypersensitivity in individuals with ASD, these studies have not (1) identified if this relationship is specific to a particular sensory modality, nor (2) included adequate control groups to test if this relationship is specific to ASD.

Objectives: (1) Determine if hypersensitivity in specific sensory modalities contributes to the presence and severity of RBs. (2) Compare the relationship between sensory sensitivity and RBs in children with and without ASD to examine whether this relationship is specific to ASD.

Methods: Parents of 70 children (ASD, n=38; TD, n=32) completed questionnaires reporting on sensory processing (Sensory Profile-2, SP-2), and RBs (Repetitive Behaviours Questionnaire-2; Repetitive Motor Movements subscale). Cognitive ability was tested and matched using the Wechsler Abbreviated Scale of Intelligence–2 (WASI-II). A two-step analysis was employed. First, correlational analyses were conducted to identify relationships between sensitivities in individual sensory modalities in TD and ASD. Second, hierarchical regressions were conducted to examine the unique contributions of sensory sensitivities while controlling for demographic variables.

Results: Correlations confirmed a strong relationship between the RBs and the Sensitivity/Sensory Subscale of the SP-2 not only in ASD (r2=0.3133, p<0.001), but also in TD (r2=0.1621, p=0.022). The relationship between RBs and processing in individual sensory modalities, however, differed between groups. In ASD, we found that RBs significantly correlated with each individual sensory modality, including audition (r2=0.1812, p=0.010), vision (r2=0.1698, p=0.013), and touch (r2=0.3206, p<0.001). In TD, however, only audition showed a significant correlation (r2=0.3154, p=0.002), not vision or touch (ps>0.05). Hierarchical regressions revealed that sensory sensitivities were predictive of RBs even when controlling for age, gender, and intelligence in both ASD (p<0.001) and TD (p=0.034) groups. Similar to the correlation findings, in TD, the main driver of RBs was auditory sensitivity (p=0.031). In the ASD group, however, touch was identified being the most predictive of RBs (p=0.015).

Conclusions: These data provide evidence that hypersensitivity contributes to RBs in individuals with ASD, but also suggest that this relationship is not restricted to ASD, but is seen in TD as well. Although hypersensitivity relates to RBs in both ASD and TD, exacerbated levels of hypersensitivity in ASD resulted in more severe RBs that surpassed a clinical threshold. While similarities were observed in the overall relationship between sensory sensitivities and RBs, this correlation was apparent across modalities in ASD, but limited to audition in TD. Furthermore, results of the hierarchical regression suggest that in ASD but not TD, sensitivity to touch is particularly predictive of RBs. In sum, these results suggest that (1) sensory sensitivities are strongly related to RBs in individuals with and without ASD, but (2) the pattern of these relationships across sensory modalities diverge between groups.