Our study aims to determine whether omega-3 fatty acid supplementation can improve sleep, mood, and behavior in children with sleep problems and symptoms of Autism Spectrum Disorder (ASD), Attention-Deficit/Hyperactivity Disorder (ADHD), or both. By using a transdiagnostic approach-focusing on specific symptoms rather than diagnostic labels-we aim to identify which children may benefit most from omega-3 supplementation, thereby enhancing inclusivity. Many previous studies have excluded children with both ASD and ADHD, or those without a formal diagnosis.