Sensory and Motor Difficulties Predict Severity of Autism Symptoms

Background: Recent research has linked motor coordination difficulties with atypical sensory processing, and demonstrated abnormalities in either sensory processing and motor coordination separately in Autism Spectrum Conditions (ASC).  However, few studies have explored both sensory and motor difficulties together, and their impact on the severity of autism symptoms.

Objectives: 1) To explore whether children with ASC have significant motor and sensory difficulties compared to typically developing (TD) children; 2) To explore whether sensory and motor difficulties predict severity of ASC symptoms.

Methods: 36 children took part: 18 (13 male, 5 female) children with ASC (mean age = 9.93 years, SD = 2.71) and 18 (7 male, 11 female) TD children (mean age = 9.16 years, SD = 1.89), matched on age and non-verbal IQ. All children completed a battery of tasks to assess performance IQ (WASI), receptive language ability (BPVS-III), motor coordination (Movement ABC), visual motor integration (BEERY-VMI), sensory processing (Sensory Profile) and autistic traits (Social Communication Questionnaire; SCQ). Autism diagnosis was confirmed and severity measured using both the Autism Diagnostic Observation Schedule General (ADOS-II), and the Autism Diagnostic Interview Revised (ADI-R). 

Results: Children with ASC scored significantly higher on parent reported autistic traits (SCQ) (p < 0.001, d = 0.831) than TD children, and significantly lower than TD children on receptive language ability (BPVS-III) (p < 0.001, d = 0.565), Movement ABC total (p < 0.001, d = 0.616), Sensory Profile total (p < 0.001, d = 0.797), and Modulation of Movement (a sensorimotor sub-component of the Sensory Profile) (p < 0.001, d = 0.565). After Bonferroni correction, there was no significant group difference in visual-motor integration (BEERY VMI) (p = 0.009, d = 0.529).  Stepwise multiple regression analyses were conducted with autism severity as outcome measures (ADOS-II, ADI-R and SCQ), and the Sensory Profile, Movement ABC, and BPVS scores as predictors. In the ASC group the BPVS and Sensory Profile were retained as significant predictors of ADI-R Communication (R² = .55, p < 0.05); the BPVS was retained as a significant predictor of ADI-R total (R² = .36, p < 0.01); the Movement ABC was retained as a significant predictor of ADOS-II Communication (R² = .46, p < 0.01) and ADOS-II total (R² = .42, p < 0.01); and the BPVS and Sensory Profile total were retained as significant predictors of the SCQ (R² = .79, p < 0.001). Modulation of Movement significantly predicted autism symptom severity across all measures (ADOS, ADI-R and SCQ) (all p < 0.05). 

Conclusions: Results show that children with ASC have significant difficulties in sensory processing, motor coordination, sensorimotor integration and receptive language compared to controls. Furthermore, after accounting for receptive language difficulties in the ASC group, the Sensory Profile significantly predicted parent reported autism symptom severity (ADI-R and SCQ), whereas the Movement ABC significantly predicted an in-person measure of autism severity (ADOS-II). Additionally, sensorimotor integration difficulties significantly predicted autism symptom severity across all diagnostic measures. These results suggest that sensory and motor difficulties together impact severity of autism symptoms.