Development of a new scale to assess hyperactivity, impulsivity, and inattentive behaviours across neurodevelopmental disorders

Difficulties with attention, impulsivity, and hyperactivity are thought to be at least as common, if not more so, among children with intellectual disability (ID) as they are in typically developing children. Although rating scales exist that are able to measure ADHD symptomatology, few if any can reliably measure the range and severity of behaviours within the ID population. Limitations to existing measures include the inappropriateness of some items for children operating within the intellectually disabled range, the lack of replicability of the factor structure, and/or that they have not been used or validated in ID populations. This study aimed to develop and evaluate a new teacher completed rating scale to measure ADHD symptomatology in children with ID. Phase 1 involved the identification of behaviours related to hyperactivity, impulsivity and inattention that were specific to children with ID, including a review of existing rating scales, diagnostic manuals, and observational and descriptive data from existing research. These behaviours were organised into a rating scale: the Scale of Attention in Intellectual Disability – Teacher version (T-SAID). Focus group discussions were held with nine health professionals (six psychologists and three paediatricians) and nine teachers who worked in special schools. Comments and feedback from these discussions were used the further refine the scale. Phase 2 involved a community survey of 176 teachers who completed the T-SAID for children aged 5 to 13 years from mild to severe/profound ID. Diagnoses of the children included autism spectrum disorder (ASD), Down Syndrome (DS) and idiopathic ID. The results indicated that the T-SAID is a reliable and valid measure for use with children with ID. It had excellent internal consistency and strong test-retest reliability. It had strong convergent validity with corresponding subscales on the Conners Third edition and the Developmental Behaviour Checklist – Teacher version and moderate divergent validity with the total score on the Vineland Adaptive Behaviour Scales – Second edition. The T-SAID also had good content validity and good discriminant validity across children with a diagnosis of ADHD and those who did not. An exploratory factor analysis of the T-SAID yielded a four factor solution: Hyperactivity/Impulsivity, Inattention, Following Instructions, and Verbal Communication. When comparing the T-SAID total score across degrees of ID, regression analyses revealed that children with severe/profound ID exhibited a greater breadth of behaviours compared with those who had mild or moderate ID, and these behaviours were significantly more severe. There was also a significant negative effect for age, suggesting that as children age their ADHD symptomatology decreases, with fewer behaviours exhibited and these behaviours being less severe. Cross-syndrome comparisons suggested that children with ASD had a significantly greater breadth of hyperactive/impulsive behaviours than those with DS or idiopathic ID. Children with ASD also had significantly greater difficulties with behaviours that make up the Verbal Communication subscale than children with DS or idiopathic ID, and that the intensity of these behaviours was also significantly greater. This study has successfully developed a reliable and valid measure for identifying ADHD symptomatology in children with ID. Further research would be needed to establish its utility in clinical, school and research settings. Integrating this scale with neuropsychological and clinical research holds exciting promise for enhancing our understanding of the nature of difficulties with attention and hyperactivity/impulsivity within the ID population.