Systematic Review: Nonverbal Learning Disability

Objective: To summarize the current state of the research literature on nonverbal learning disability (NVLD), including criteria used to define NVLD in research contexts and the quality of the extant research; and to determine what research can tell us about ways in which NVLD is distinct from DSM neurodevelopmental disorders and typical development. Method: A systematic search of 7 databases was conducted to identify research on NVLD published through February 2019. Criteria used to define NVLD were extracted from identified studies and sorted by category. Each study was assessed for risk of bias and rated “good,” “fair,” or “poor;” findings from studies rated good or fair were summarized. Results: A total of 61 articles (63 studies) met inclusion criteria. There was great heterogeneity in the criteria used to define NVLD. Deficits in visuospatial ability/intelligence was the most common criterion used, followed by discrepancy between verbal and nonverbal intelligence (VIQ>PIQ split of 10 or greater). All studies were cross-sectional and most included small, poorly described samples. Most studies focused on children and young adolescents. Eight studies were rated as good, 42 as fair, and 13 as poor. Review of results from the 50 good or fair studies suggest that there is sufficient evidence that youths with NVLD (as defined by significant deficits in visuospatial abilities) can be clearly differentiated from their typically developing peers, those with verbal learning disorders, and from other clinical groups (eg, individuals with high functioning autism). Conclusion: A standard set of criteria for determining an NVLD diagnosis would greatly improve research studies and the possibility of inclusion in the DSM and the International Classification of Diseases.