Retinal nerve fibre layer, and ganglion cell layer thicknesses in children with ADHD: associations with subtypes and symptom severity

Background To investigate retinal nerve fibre layer (RNFL) and ganglion cell layer (GCL) thickness in different attention-deficit/hyperactivity disorder (ADHD) subtypes and their association with ADHD symptom severity. Methods This is a cross-sectional study included children aged 6–8 years in Hong Kong. ADHD diagnoses were made by psychiatrists based on ICD-10 criteria. Results Among 6431 children included in the study, 309 (4.80%) were diagnosed with ADHD and 6122 served as controls. Children with ADHD showed thinner p-RNFL, m-GCL, and p-GCL than controls ( P = 0.002; P = 0.03; P = 0.003, respectively). Among the 309 ADHD, 149 were categorized as the combined (C) type, 74 as the Inattentive (IA) type, 39 as the hyperactive/impulsive (HI) type. The ADHD-C subtype exhibited thinner p-RNFL (mean difference [MD] = -2.47, P = 0.03), m-GCL (MD = -1.10, P = 0.03), and p-GCL (MD = -0.85, P = 0.007) than controls. The p-RNFL, m-GCL, and p-GCL thicknesses showed a decreasing trend across ADHD subtypes, being thickest in the ADHD-HI, followed by the IA, and then the C subtype ( P = 0.04, P = 0.005, and P = 0.04, respectively). Higher SWAN-combined scores were associated with thinner p-RNFL, m-GCL, p-GCL, and m-RNFL ( P = 0.04; P = 0.002; P = 0.005; P = 0.02, respectively). Conclusion RNFL and GCL thicknesses varied across ADHD subtypes. The combined subtypes exhibited thinner measurements than controls. An overall trend toward thinner RNFL and GCL thicknesses was observed across subtypes. RNFL and GCL thicknesses were negatively associated with severity of combined ADHD symptoms. Clinical trial number Not applicable.