Differential diagnosis: Understanding nonverbal learning disorder and autism spectrum disorder

Previous research has suggested that children with Nonverbal Learning Disorder (NLD) share similar clinical profiles to those with autism spectrum disorder (ASD). Three groups of children were identified for the purpose of the current study: NLD (n = 41), ASD (n = 55), and ASD with a NLD profile (n = 17). Children who met DSM-5 criteria for ASD after a neuropsychological evaluation were included in this sample. The NLD group was defined by VSI < VCI, with a minimum of a 15-point discrepancy between indices and average to above average verbal intelligence, whereas children who met DSM-5 criteria for ASD and also demonstrated visual-spatial deficits met criteria for the NLD + ASD group. As anticipated, the ASD group performed better on measures of VSI compared to the NLD and ASD + NLD groups. There was not a significant difference between groups on measures of visuomotor and construction abilities, visual integration, motor processing speed, and academic achievement. No significant differences between groups were found on the CBCL/TRF Social Problems, Attention Problems, or Internalizing/Externalizing Problems scales, indicating similar phenotypes. However, there was a significant difference between groups on the Thought Problems subscale for teacher and parent rating scales. Results corroborate previous research indicating similarities between neuropsychological profiles and suggest that the ASEBA Thought Problems scale may aid in discriminating individuals with ASD from those with NLD.