Sensory Processing Abnormalities – a Constant Across the Autistic Spectrum

Background: Sensory processing plays a fundamental role in interpreting and managing a persons social environment.  Also sensory processing abnormalities have been well documented in both children and adults with an autism spectrum disorder (ASD). These abnormalities include both hyper-sensitivity and hypo-sensitivity across all sensory modalities, along with unusual sensory-based behaviours.  Hence sensory processing symptoms were included in the new  Diagnostic Statistical Manual 5^th Edition (DSM-5) criteria for ASD. However, it is unknown whether sensory traits are related to the clinical severity of core ASD symptoms as measured by the Autism Diagnostic Interview (ADI) and the Autism Diagnostic Observation Schedule (ADOS).

Objectives: We conducted the first study to evaluate the relationship between self-reported sensory traits and clinical ASD severity in a population of adults referred for a diagnosis of ASD.

Methods: We included adults (age 18-63) (N=67) referred to a national specialist ASD outpatient service on account of suspected ASD. The patients received a diagnostic assessment using the ADI-R and/or the ADOS Module 4. The patients also completed the widely used, validated self-report Adult/Adolescent Sensory Profile (AASP) questionnaire which includes four subscales: Low Registration, Sensation Seeking, Sensory Sensitivity, and Sensation Avoiding. An additional healthy control sample of 749 individuals who completed the AASP was used to determine the ‘normal range’ of scores on this measure..

Results: Sensory scores in the patient sample were highly abnormal - 50.0% of the patient group scored above the 95^th percentile of the control group, while 87.8% scored above the control population median.  Unexpectedly, however, we found no association between self-reported total AASP sensory scores and either ADOS (r = 0.02, p = 0.93) or ADI (r = -0.334, p = 0.07) total scores in the patient group. Nor were there any significant correlations between any of the four AASP subscales, and any ADI or ADOS symptom domain (all p > 0.1 uncorrected).

Conclusions: Self-reported sensory symptoms are not related to clinical ASD severity in an adult population. It is possible that they are explained by abnormalities in different neural systems than those underpinning most other core symptoms of ASD. This finding has clinical implications, as it suggests that sensory processing abnormalities, which are known to be associated with distress (Jones et al. 2003), should be probed for even in individuals who do not score highly on measures such as the ADI and the ADOS.