Title: Diagnosing Autism and ADHD in Adults by Observation Rather Than Interrogation: A Longitudinal, DBT-Informed Assessment Model

Article type: Analysis

Author: Marie Meronym

Affiliation: Independent service design contributor

Correspondence: Email: mariemeronym@gmail.com

Competing interests: The author has received clinical confirmation of autism (Part 1 assessment, October 2025) and combined ADHD (January 2026). Formal diagnostic documentation remains incomplete due to financial barriers to Part 2 assessment and unresolved GP access issues. No financial competing interests are declared. 

Diagnosing Autism and ADHD in Adults by Observation Rather Than Interrogation:

A Longitudinal, DBT-Informed Assessment Model

Article type: Analysis
Author: Marie Meronym
Affiliation: Independent service design contributor
Correspondence: mariemeronym@gmail.com
Competing interests: The author has received clinical confirmation of autism (Part 1 assessment, October 2025) and combined ADHD (January 2026). Formal diagnostic documentation remains incomplete due to financial barriers to Part 2 assessment and unresolved GP access issues. No financial competing interests are declared. 

Summary points

•        Late diagnosis of autism and ADHD in adults, particularly women, is well documented and remains common in NHS services. [1] [2] [3]

•        Current assessment pathways rely heavily on single-point interviews and self-report tools that are poorly suited to masked or late-presenting adults. [4] [5] [6] [7]

•        Neurodevelopmental conditions are defined by patterns of functioning over time, yet current diagnostic models rarely allow longitudinal observation. [3] [5]

•        A diagnostic pathway adapted from existing Dialectical Behaviour Therapy (DBT) service structures could improve diagnostic accuracy while remaining scalable within current NHS infrastructure. [8] [9] [10] [11] [12]

Introduction

Late diagnosis of autism and attention-deficit/hyperactivity disorder (ADHD) in adults is increasingly recognised as a significant clinical and service-delivery problem in the UK and internationally. Women in particular are frequently diagnosed only in adulthood, often after many years of contact with mental health services for anxiety, depression, emotional dysregulation, or recurrent burnout. [1] [2]

Qualitative research consistently shows that late-diagnosed adults often recognise neurodevelopmental difference long before formal diagnosis, yet encounter repeated barriers to referral and assessment. [1] [3] [4] These barriers include gendered diagnostic stereotypes, masking and compensation strategies, and assessment tools that rely heavily on neurotypical language and retrospective self-report. [4] [5] [6] As a result, individuals may be excluded from diagnosis despite substantial functional impairment and lifelong neurodevelopmental differences. [3] [7]

This article argues that current adult autism and ADHD assessment models are structurally misaligned with the presentation patterns of many late-diagnosed adults. It proposes a longitudinal, observation-based diagnostic pathway adapted from existing Dialectical Behaviour Therapy (DBT) service models. By using repeated observation across individual and group contexts, this model supports more accurate diagnosis, reduces misattribution, and provides safer post-diagnostic care.

Limitations of current adult diagnostic pathways

Standard adult autism and ADHD assessments typically involve one or two clinical appointments supported by self-report questionnaires and, where available, informant histories. While efficient, this model has several systemic limitations when applied to adults who mask or compensate effectively.

Single-point assessments disproportionately reward verbal fluency, insight, and social competence—all of which may be highly developed in late-diagnosed adults through sustained effort rather than neurotypical processing. [5] [6] Screening tools and diagnostic interviews also rely on language that presumes normative social experiences, often requiring individuals to translate complex internal states into externally framed descriptors. [9] Brief assessments further limit opportunities to observe consistency, variability, or contrast in functioning across contexts. [3] [7]

Neurodevelopmental conditions are defined by pervasive patterns over time, yet current diagnostic models often assess performance under optimal, time-limited conditions. This mismatch increases the risk of false negatives and misattribution to alternative psychiatric diagnoses. [3] [7] [8]

Why longitudinal observation matters

Autism and ADHD are enduring neurodevelopmental differences that shape cognition, communication, and regulation across the lifespan. Diagnostic confidence improves when clinicians can observe patterns of functioning longitudinally and across environments.

Longitudinal observation allows clinicians to distinguish masking from an absence of difficulty. It helps identify cognitive and social load under shared attention, observe variability in regulation across weeks, and recognise consistent narrative and relational patterns. [3] [4] [5] [6] Despite this, few adult diagnostic pathways incorporate structured observation beyond the clinical interview.

DBT as an existing structural scaffold

DBT services within the NHS already operate a service architecture that addresses several of these structural gaps. Core features include continuity of clinician contact, parallel individual and group sessions, structured and predictable social environments, and rolling cohort intake. [12]

While DBT is designed as a therapeutic intervention, its service structure provides a viable scaffold for a redesigned diagnostic pathway. The clinical literature already recognises that DBT delivery mechanisms can be adapted to accommodate cognitive processing differences without abandoning the core model. [13] This proposal does not suggest using DBT content to diagnose neurodevelopmental conditions, but rather adapting its structure to enable longitudinal observation.

Proposed diagnostic pathway

The proposed pathway is a rolling, three-month neurodevelopmental assessment programme embedded within existing DBT-style service structures and delivered by a multidisciplinary team.

Participants receive:

•        one weekly structured group session

•        one weekly individual session with a named nurse

•        observation by a consistent team including a nurse and a psychologist and/or psychiatrist

New participants join the programme at regular intervals. This "rolling cohort" model is crucial because it reduces the severe delays associated with fixed-cohort models, where patients must wait months for a new group to form.

Role of individual sessions

Weekly individual sessions provide an optimal-conditions environment. Here, the named nurse can observe narrative organisation and coherence, emotional and sensory language, interpretation of social and relational events, executive functioning, and consistency of presentation over time.

This context captures how individuals present when regulated and supported. This is often the setting in which many autistic and ADHD adults appear outwardly "typical" and are therefore frequently missed in standard, high-pressure assessments. [4] [5] [6]

Role of group sessions

Group sessions provide a contrasting but predictable social context. Observations focus on social timing and reciprocity, masking behaviours and effort, cognitive load under shared attention, responses to group norms and structure, and changes in presentation across sessions. [4] [5] [6]

The same nurse attends both individual and group sessions, allowing direct comparison of presentation across contexts. A psychologist or psychiatrist is present for group facilitation and diagnostic observation. This dual-context model enables the identification of neurodevelopmental patterns that may not be evident in interview settings alone.

Diagnostic decision-making and outcomes

Diagnostic conclusions are informed by longitudinal observation across contexts, multidisciplinary discussion, and the consistency of behavioural and narrative patterns rather than single responses.

At the end of the three-month assessment period, individuals meeting diagnostic criteria receive a formal diagnosis, while those who do not receive a clear formulation and appropriate onward referral.

Recognising the vulnerability associated with late diagnosis, individuals who receive an autism or ADHD diagnosis remain within the programme for up to four additional weeks. This phase supports psychoeducation, stabilisation, and transition planning. This prevents the common "diagnose and discharge" cliff edge and mitigates the distress commonly reported following abrupt discharge. [10]

Implications for services

This model has the potential to improve diagnostic accuracy for masked and late-presenting adults, reduce inappropriate exclusion from neurodevelopmental pathways, and decrease repeated presentations to generic mental health services. By utilising existing DBT infrastructure, it supports scalability and cost-effectiveness while increasing clinician confidence through pattern-based assessment. [8] [11]

Conclusion

Late diagnosis of autism and ADHD reflects limitations in current assessment models rather than a lack of patient insight. A longitudinal, observation-based diagnostic pathway adapted from DBT service structures offers a pragmatic, humane, and evidence-aligned alternative to current models. By prioritising replication, contrast, and continuity, services can better identify neurodevelopmental differences and support adults who have historically been overlooked. Pilot evaluation is warranted.

References

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[11] NICE. Autism spectrum disorder in adults: diagnosis and management (CG142). London: NICE; 2012.
[12] Linehan MM. Cognitive-Behavioral Treatment of Borderline Personality Disorder. New York: Guilford Press; 1993.
[13] Brown J. Improving Accessibility to Dialectical Behaviour Therapy for Individuals with Cognitive Challenges. In: The Oxford Handbook of Dialectical Behaviour Therapy. Oxford Handbooks Online; 2017.