Autism Spectrum Disorder in Childhood: Early signs and the impact of delayed diagnosis

Abstract

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental condition whose defining features often emerge before school age, although formal diagnosis may still occur after several missed opportunities for recognition. This narrative review critically analyzes early signs of ASD in childhood and the clinical, developmental, family, educational, and health-system consequences of delayed diagnosis. A selective, interpretive synthesis of guidelines, surveillance reports, systematic reviews, validation studies, and clinically relevant observational evidence was conducted, prioritizing publications from the last 15 years while retaining foundational diagnostic and screening sources. Early manifestations include reduced social reciprocity, atypical eye contact, limited response to name, delayed or unusual communication, restricted and repetitive behaviors, sensory differences, motor atypicalities, and developmental regression in some children. Evidence indicates that structured developmental surveillance, autism-specific screening, culturally adapted instruments, and rapid referral pathways can shorten the diagnostic pathway, but inequalities persist by sex, race, socioeconomic position, language, geography, and availability of specialized services. Delayed diagnosis may postpone early intervention, intensify family stress, increase school difficulties, contribute to mislabeling or diagnostic overshadowing, and widen disparities in access to care. The review concludes that earlier recognition should not depend exclusively on a definitive label; rather, children with developmental concerns should receive timely, individualized, family-centered support while diagnostic clarification proceeds.