Increased Prevalence of Psychiatric Disorders in Children with RASopathies: Comparing NF1, Noonan Syndrome Spectrum Disorder, and the General Population

<b>Background/Objectives</b>: Neurofibromatosis type 1 (NF1) and Noonan syndrome spectrum disorders (NSSD) are the most common RASopathies, resulting from germline mutations that affect the RAS-MAPK signaling pathway. Both are associated with increased risk for neurodevelopmental and psychiatric conditions, yet few studies have used structured diagnostic interviews to compare their psychiatric comorbidities. <b>Methods:</b> We conducted clinician-administered DSM-5 diagnostic assessments (KSADS) in 123 children with RASopathies (NF1 = 29, NSSD = 94; ages 5-15). Diagnosis prevalence was compared within each group and to population-based estimates. <b>Results:</b> Psychiatric diagnoses were highly prevalent, at 79.3% in NF1 and 76.6% in NSSD, with ADHD (NF1 = 72.4%, NSSD = 51.1%) and anxiety disorders (NF1 = 37.9% and NSSD = 43.6%) being the most common, rates substantially higher than those reported in general population estimates. Behavioral and sleep disorders were identified in approximately 25% of both groups. Notably, social anxiety disorder was identified in 14.9% of NSSD but not in NF1. Full-scale IQ did not significantly differ by diagnosis status. Specific anxiety disorders, elimination disorders, obsessive-compulsive disorder, and post-traumatic stress disorder were characterized, expanding the known psychiatric phenotype of RASopathies. <b>Conclusions:</b> Children with NF1 and NSSD demonstrate similarly high rates of ADHD, anxiety, and behavioral disorders compared to the general population; in addition, we report sleep disorders in NSSD and characterize psychiatric disorders not previously described in RASopathies. The shared psychiatric profiles may reflect the common effect of RAS-MAPK pathway dysregulation on psychiatric outcomes. These findings highlight the need for early, syndrome-informed mental health screening and intervention in the clinical care of individuals with RASopathies.