Nonverbal learning disability has been identified as a neurodevelopmental disorder for over 50 years, but it is not listed as a diagnosis in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). It has been hard to develop a set of criteria for NVLD that are generally agreed-upon. In the Journal of the American Academy of Child & Adolescent Psychiatry (February, 2022), an editorial by Irene Mammarella, Ph.D. advocates for the development of clear diagnostic criteria, and presumably, this would allow for the inclusion of NVLD as a diagnosis in the DSM-5 (and subsequent editions).
A Google search for NVLD yields several diagnostic criteria: (1) normal verbal skills with deficits in visual construction abilities; (2) math reasoning difficulties; (3) visual memory difficulties; (4) social difficulties.
The testing database that we have at The Neuropsychology Service tracks 149 measures, and as of July, 2022, we have 348 cases that fit the NVLD diagnostic criteria listed above.
The average Verbal Comprehension Index score for the group was 100, so our NVLD population exhibited verbal skills in the average range. The average Full Scale IQ score was 91, and this lower score was due to problems with visual-spatial tasks (and processing speed tasks). Our data comes from both the WISC-IV and the WISC-V, and the Block Design and the Matrix Reasoning subtests are common to both batteries.
The average Block Design scaled score was 6.9; the average Matrix Reasoning scaled score was 7.6. A scaled score of 10 would be average (the standard deviation is 3). The low Block Design score pattern is significant and the low Matrix Reasoning pattern borders on significance.
In academic testing, our data comes from the Wechsler Individual Achievement Test – Third Edition (WIAT-III) and the Wechsler Individual Achievement Test – Fourth Edition (WIAT-4). The average math computation standard score was 92. The word reading average was 99; the spelling average was 98. The math computation score, then, was typically lower than the single word reading and the spelling scores.
Developmentally, our NVLD group started to use sentences at 24 months (average); the group average for walking independently was 13 months (average).
This data cannot be considered a scientific sample. It represents data collected in a clinical practice on the North Shore of Massachusetts. No attempt has been made to adjust the data to match the US population in general.
Regarding the DSM-5, Psychiatrists have used psychological testing data to help with the diagnosis of intellectual disabilities. It may be that testing data is required for the diagnosis of NVLD also.