Oral Language Skills of Children and Adolescents with Neurofibromatosis Type 1: a Systematic Review and Meta-analysis

This meta-analysis aimed to robustly estimate mean differences in oral language skills between children and adolescents with neurofibromatosis type 1 (NF1) and the general population, and to examine potential moderators contributing to variability in these group differences. A comprehensive literature search was conducted across Scopus, PsycINFO, Web of Science, PubMed, and ProQuest on March 31, 2025, yielding 2,531 records. Among them, 44 studies met inclusion criteria, comprising 2,479 individuals with NF1 (45.10% female; M_age = 8.58 years, SD = 3.81). Results showed that individuals with NF1 performed significantly lower than controls in overall oral language skills (n = 45, k = 131, g = -0.66, 95% CI [-0.78, -0.54], I² = 82.91%), as well as in all subdomains including core language skills (g = -0.79, 95% CI [-0.99, -0.58]), expressive language (g = -0.63, 95% CI [-0.80, -0.47]), receptive language (g = -0.59, 95% CI [-0.79, -0.39]), and phonological awareness (g = -0.68, 95% CI [-0.86, -0.51]). These group differences remained consistent across studies that vary in sample mean age, sex composition, NF1 inheritance mode, ADHD or learning disorder diagnosis, intelligence, working memory, comparison group type, sampling resources, and measures. The findings highlight the need for targeted interventions to improve oral language skills among individuals with NF1 and emphasize the importance of exploring underlying factors using individual-level data and large representative samples.