Sensory processing difficulties have been commonly described in autism spectrum disorder (ASD) and have been considered a prominent feature in the clinical presentation. A sensory processing dysfunction subscale has been added recently to the restrictive and repetitive behaviors (RRB) domain criteria for ASD in the new DSM 5.
The current research aims at elucidating the characteristics and impact on functioning of two common major sensory processing modalities, hypo-and hyper-sensitivities in ASD. Firstly, the frequencies of sensory hypo-and hyper-sensitivities were assessed in the entire study group. Secondly, the association between having sensory hypo- and/or hypersensitivity and the severity of the clinical phenotype in autism symptoms, cognitive ability and adaptive skills were evaluated.
The study was conducted at ‘The Autism Center’ a national tertiary center involved in diagnosis, treatment and research in ASD. The cohort included 679 participants (590 males, 89 females) diagnosed with ASD, within the age range of 18 m.-15 y. (M=44.1m.±28.7). Participants underwent a neurological assessment and behavioral and cognitive evaluations by a skilled interdisciplinary team. Assessment of ASD was obtained using standardized tests, the Autism Diagnosis Interview-Revised (ADI-R), and the Autism Diagnosis Observation Schedule (ADOS). Autism severity was assessed using the ADI-R algorithm, the ADOS algorithm, and the ADOS severity scale scores. Cognitive and developmental abilities (IQ/DQ) were assessed using standardized tests and adaptive skills using the Vinland adaptive behavior scales (VABS). Information regarding sensory processing dysfunction specifically in hypo-and hyper-sensitivities, were obtained from the relevant ADI-R items with scores of one or above. Sensory hyposensitivity referred to both having seeking behaviors and tolerance to pain. Sensory hypersensitivity referred to active avoidance of one or more sensory modalities.
Sensory hyposensitivity was observed in 70.4% and sensory-hypersensitivity in 66.0% of the ASD group. The ASD subgroup with sensory hyposensitivity had significantly more severe autism symptoms than the subgroup without sensory hyposensitivity. The sensory hyposensitivity subgroup had significantly higher ADI-R scores in all the three examined domains (social interaction, communication and RRB) (p<.001), significantly higher scores in the ADOS algorithm, and in the autism severity scale scores (p<.001) than the subgroup without hyposensitivity. Regarding cognitive ability, the sensory hyposensitivity subgroup had significantly lower IQ/DQ scores than the subgroup without hyposensitivity. Regarding adaptive skills, the subgroup with sensory hyposensitivity had significantly lower VABS scores than the subgroup without hyposensitivity in: communication, daily living skills and socialization domains (p<.001). In contrast, the subgroup with sensory hypersensitivity had only significantly higher ADI-R scores than the subgroup without sensory hypersensitivity and only in the RRB domain (p<.001). No significant differences in ADOS algorithm, autism severity scale, IQ/DQ and VABS scores were noted between the groups with and without sensory hypersensitivity.
In ASD, having sensory hyposensitivity is highly associated with more severe clinical presentation affecting numerous developmental domains. It is suggested this clinical phenotype has a unique neurobiological origin. The current findings emphasize the importance of including sensory processing dysfunction as a core criterion for ASD and the need for developing specific treatment strategies to address sensory hyposensitivity.
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