Clinical Constructs and Historical Insights of the Autism Spectrum Disorder in adults

OBJECTIVE: Autism spectrum disorder (ASD) is clinically heterogeneous, and adult presentations, especially among individuals requiring Level 1 support, may be subtle, shaped by adaptation, and obscured by comorbidity and diagnostic overshadowing. We review the historical evolution of autism-related constructs and their implications for recognising and interpreting ASD in adults. METHODS: We conducted a narrative review in MEDLINE (PubMed). Searches combined "autism", "autism spectrum disorder", and "ASD" with predefined constructs (central coherence, theory of mind, social skills, sensory processing differences, repetitive behaviours, restricted and intense interests, executive functions, alexithymia, sleep disturbances, motor abnormalities, and camouflaging). A second search focused on adult autism (adulthood, autistic adults, late diagnosis, and compensatory mechanisms). Grey literature was also considered; publications available up to December 2025 were included. RESULTS: The literature reflects a progressive refinement of the autism construct from descriptive behavioural syndromes to mechanism-oriented models that better accommodate phenotypic variability across development. In adults, these constructs help explain how pragmatic-communication difficulties, rigidity, intense interests, sensory reactivity, and executive-attentional differences can coexist with preserved language and intelligence. Recognition of compensatory strategies and social camouflaging helps explain delayed or missed diagnoses and associated distress. Shifts in diagnostic boundaries and awareness complicate inference from apparent prevalence increases. CONCLUSION: A historically grounded, construct-based framework can improve recognition of clinically meaningful adult ASD, sharpen differential diagnosis amid comorbidity, and support nuanced interpretation of changing diagnostic practices and epidemiological findings. It may inform individualized assessment and support planning as occupational, relational, and adaptive demands increase across adulthood substantially.