Barriers to an adult autism diagnosis: limitations of the ADOS-2

Increasing numbers of adults are recognising autism in themselves and seeking a diagnostic assessment. In this blog, we explore one barrier that can impede and confound a formal diagnosis: the ADOS-2.

The Autism Diagnostic Observation Schedule (ADOS)

Although the ADOS-2 is widely used and is often described as a “gold-standard” observational measure within a comprehensive autism diagnostic assessment, our extensive clinical experience with the diagnostic assessment of adults and related research has identified significant issues with the ADOS-2's psychometric properties and its sensitivity to the nuances of adult presentations of autism.

Psychometric Limitations

Research has raised concerns about the sensitivity of ADOS-2 Module 4 for some autistic adults with average or above-average intellectual ability. Across adulthood, social communication can be supported by learned conversational scripts, rehearsed gestures, and compensatory strategies (often described as camouflaging).  In a brief observational context, these adaptations may reduce the salience of observable autistic social communication features and may contribute to under-identification (false negative results) if ADOS-2 scores are interpreted without integration of developmental history and collateral information (Lai et al., 2011; Langmann et al., 2017).

Evidence also indicates potential limitations in specificity in community mental health contexts. In adults with complex psychiatric presentations, ADOS-2 classifications can include false positives, including among adults experiencing psychosis, highlighting that elevated scores may sometimes reflect overlapping social cognitive or communication difficulties rather than autism per se. This supports cautious interpretation of ADOS-2 results and a structured differential diagnostic process when co-occurring psychiatric conditions are present (Maddox et al., 2017).

ADOS-2 assessment tasks and acceptability in adulthood

The ADOS-2 includes components that can be appropriate for adult assessment, including structured conversational prompts that explore social experiences, relationships, and emotional understanding. However, some Module 4 tasks can feel artificial or developmentally incongruent for some adults, such as constructing a story from picture materials or enacting actions through gesture. Where tasks feel mismatched to adult communication norms, this can reduce comfort and rapport, and may influence engagement during the session and the perceived credibility of the assessment process.

Clinical judgement remains central in adult autism diagnosis. Best practice relies on a comprehensive clinician-led assessment that integrates developmental history, current functioning across contexts, collateral information, and standardised tools such as the ADOS-2. Within this approach, the ADOS-2 is treated as one source of evidence rather than a determinant of diagnostic outcome.

Taken together, these limitations reinforce why adult autism and AuDHD assessment requires more than procedural administration of standardised instruments. Our upcoming masterclass is designed to strengthen clinicians’ discipline-specific knowledge and applied skills in the diagnostic assessment of autistic and AuDHD adults. It focuses on integrating DSM-5-TR criteria with developmental history, lived experience, and differential diagnosis in the context of co-occurring presentations, so that assessment conclusions are accurate, respectful, and clinically useful.

For clinicians seeking to extend learning beyond diagnostic assessment, Masterclass Day 2, Support and Therapy for Autistic and/or AuDHD Adults, focuses on translating assessment understanding into neurodiversity-affirming care. It examines biopsychosocial contributors to mental health in neurodivergent adults, outlines adaptations across therapeutic modalities, and provides practical strategies to support identity development, safe and supported unmasking, and responsive care for common co-occurring concerns, including burnout, depression, anxiety, and trauma.

References

Lai, M. C., Lombardo, M. V., Pasco, G., Ruigrok, A. N., Wheelwright, S. J., Sadek, S. A., ... & Baron-Cohen, S. (2011). A behavioral comparison of male and female adults with high functioning autism spectrum conditions. PloS one, 6(6), e20835.

Langmann, A., Becker, J., Poustka, L., Becker, K., & Kamp-Becker, I. (2017). Diagnostic utility of the autism diagnostic observation schedule in a clinical sample of adolescents and adults. Research in Autism Spectrum Disorders, 34, 34-43.

Maddox, B. (2020). The Accuracy of the ADOS-2 in Identifying Autism Among Adults with Complex Psychiatric Conditions., 1-2. https://doi.org/10.1007/978-1-4614-6435-8_102372-1

Nayyar, J. M., Stapleton, A. V., Guerin, S., & O'Connor, C. (2025). Exploring lived experiences of receiving a diagnosis of autism in adulthood: A systematic review. Autism in Adulthood, 7(1), 1-12. https://doi.org/10.1089/aut.2023.0152