Background: Autism spectrum disorder (ASD) is traditionally considered a neurodevelopmental condition typically identified in early childhood. However, a substantial proportion of individuals receive their first diagnosis only in adolescence or adulthood, which may affect mental health, access to support, and overall quality of life. Objective: This review examines late diagnosis of ASD in adults and summarizes current evidence on factors contributing to diagnostic delay, including camouflaging behaviours, psychiatric comorbidities, and suicidality. Methodology: A literature search was conducted using PubMed and Google Scholar to identify studies published between 2000 and 2025. Search terms included combinations of “autism,” “adult diagnosis,” “diagnostic delay,” “camouflaging,” “psychiatric comorbidity,” and “suicide.” Studies focusing on adult populations, diagnostic pathways, and mental health outcomes were prioritized. In total, 36 publications were included. Due to methodological heterogeneity across studies, findings were synthesized narratively. Results: Definitions of late ASD diagnosis vary across studies, with inconsistent age thresholds. Many adults diagnosed with ASD report prior psychiatric diagnoses, although registry data indicate that a substantial proportion had no documented psychiatric conditions during childhood. Camouflaging behaviours, particularly among women, may contribute to delayed recognition and are associated with increased psychological distress. Adults with ASD show elevated rates of depression and anxiety, with lifetime prevalence of depressive disorders reaching 30–40% in some studies. Population-based research also indicates increased risk of suicidality. Conclusions: Late identification of ASD in adulthood is associated with complex diagnostic pathways and a high prevalence of psychiatric comorbidity. Improving awareness of adult autism among clinicians may contribute to earlier recognition and more appropriate support for affected individuals. Further research is needed to refine diagnostic tools and to better understand long-term mental health outcomes in people diagnosed with ASD later in life.
Makowska et al. (Mon,) studied this question.