Abstract
Neurodiversity research has historically emphasized early diagnosis of conditions such as Autism Spectrum Disorder (ASD), Attention-Deficit/Hyperactivity Disorder (ADHD), and Dyslexia, aiming to leverage timely interventions. However, many individuals discover their neurodivergent identity only in adulthood or even old age. Growing evidence indicates that a considerable portion of adults remain undiagnosed until later in life, challenging assumptions that diagnosis is strictly a childhood milestone. This paper examines the multifaceted implications of late diagnosis. First, it explores identity formation and re-conceptualization of self after a midlife or later-life diagnosis. Second, it investigates retrospective coping strategies developed without formal support. Third, it identifies service gaps for older adults, including barriers in healthcare, social services, and employment. Drawing on research that estimates the prevalence of underdiagnosed neurodivergence among adults, cross-national policy comparisons, and data illustrating the economic burdens on healthcare systems, this review underscores the urgent need to address late-life diagnosis through tailored interventions, policy reforms, and improved clinical training. In doing so, it highlights a critical gap in current practice and scholarship: the recognition and support of neurodivergent identities throughout the entire lifespan.

1. Introduction
Early diagnosis of neurodevelopmental conditions has traditionally been viewed as essential for implementing effective interventions and maximizing positive outcomes (Lai, Lombardo, & Baron-Cohen, 2014). However, increasing data from epidemiological and clinical research suggest that a significant proportion of individuals with ASD, ADHD, and other neurotypes remain undiagnosed until adulthood or later (Brugha et al., 2011; Kessler et al., 2006). In the United States, for example, studies estimate the prevalence of adult ADHD at around 4.4%, yet historically, fewer than 20% of these adults receive a diagnosis in childhood, leaving many to discover their condition much later (Kessler et al., 2006; Faraone & Biederman, 2005). In the United Kingdom, the Adult Psychiatric Morbidity Survey found around 1% of adults meet criteria for ASD, closely mirroring childhood prevalence rates, yet the majority had never received a formal diagnosis (Brugha et al., 2011).

Late diagnosis can occur for various reasons: evolving diagnostic criteria, limited awareness among clinicians and individuals themselves, and cultural factors that shape the understanding of neurodivergent traits (Lewis, 2016; Bargiela, Steward, & Mandy, 2016). This late-life recognition often leads to profound personal reflection and identity reformation, prompting reconsideration of past struggles and successes.

This paper focuses on three key research angles:

1. Identity Formation in Later Life: Understanding how a newly discovered neurodivergent identity affects self-concept, relationships, and career trajectories.
2. Retrospective Adaptation: Exploring how late-diagnosed individuals developed coping strategies in the absence of early recognition.
3. Service Gaps for Older Adults: Identifying healthcare, social support, workplace policy gaps, and the economic implications of late or missed diagnoses.

By examining these angles, we move toward a more inclusive understanding of neurodiversity that extends beyond childhood and into every stage of adulthood, carrying lessons for international health policies and economic planning.

2. Identity Formation in Later Life

2.1. Reframing Self-Concept and Interpersonal Dynamics
For late-diagnosed adults, the discovery of a neurodivergent identity can reframe a lifetime of unexplained challenges (Lewis, 2016). In ASD, older individuals often reinterpret difficulties in social communication, sensory sensitivities, and rigid routines as characteristics of their neurotype rather than personal failings. Similarly, adults diagnosed with ADHD in midlife may recast what they once perceived as moral shortcomings or laziness into legitimate neurocognitive differences (Barkley, Murphy, & Fischer, 2008).

This new self-understanding can reduce self-blame, improve self-esteem, and facilitate more open dialogues with family and friends. However, not all repercussions are straightforward. Partners and children may need time to adjust, and established relationship dynamics may shift as the individual seeks accommodations or understanding that were previously absent (Belek, 2019).

2.2. Implications for Career Trajectories
Professionally, late diagnosis can illuminate longstanding work-related struggles. Individuals who previously lacked justification for their organizational difficulties, time-management problems, or challenges in group settings may now recognize the influence of previously undiagnosed ADHD or ASD traits. Some may seek new careers better aligned with their cognitive style; others might request workplace accommodations for the first time, potentially improving productivity and job satisfaction. Still, many older adults encounter workplaces unfamiliar with supporting late-diagnosed employees, necessitating policy improvements (Young & Bramham, 2012).

3. Retrospective Adaptation: Coping Without Formal Recognition

3.1. Masking, Compensation, and Self-Help Strategies
Adults who receive diagnoses late in life often reflect on how they managed to adapt without formal support. Masking—suppressing or camouflaging neurodivergent traits—can be a common coping mechanism, enabling individuals to meet societal expectations at great personal cost (Bargiela et al., 2016). Studies of late-diagnosed autistic women, for instance, reveal that they often adopted intricate social scripts to navigate social interactions, leading to stress and eventual burnout.

In ADHD, many older adults report relying on self-created organizational systems, physical exercise, or choosing jobs that minimize executive function demands. Such self-directed strategies highlight human resilience but also underscore lost opportunities for earlier interventions that could have reduced distress and enhanced life satisfaction (Treweek, Woodhouse, & Martin, 2019).

3.2. Reinterpreting Past Experiences
Armed with a late-life diagnosis, individuals often revisit their personal histories, reframing academic failures, strained relationships, or career instability in terms of unmet support needs rather than moral or intellectual deficits (Lewis, 2016). This retrospective reinterpretation can foster self-compassion and motivate the pursuit of tailored therapies, occupational strategies, or social groups that now make sense in the context of a known neurodivergent identity.

4. Service Gaps for Older Adults

4.1. Healthcare System Limitations and International Variability
Current healthcare infrastructures, across both high-income and low-middle-income countries, primarily focus on early diagnosis and pediatric intervention. In Europe and North America, while awareness of adult ADHD and ASD is growing, many clinicians remain undertrained in identifying these conditions in older adults (Crane et al., 2019; Happé & Charlton, 2012). In countries with universal healthcare, such as Norway or the UK, older adults may more easily access diagnostic evaluations, but long wait lists and scarce specialists remain barriers. In contrast, nations with limited mental health resources often struggle to provide any adult diagnostic services, reflecting stark global disparities (Brugha et al., 2011; NICE, 2012/2021).

4.2. Social Support Structures and Aging Demographics
As populations age globally, more individuals reach older adulthood without having been diagnosed. Social services and community supports for neurodivergent seniors are often minimal or non-existent, leaving families to navigate care with scant guidance. International comparisons reveal that Northern European countries, such as Sweden and Denmark, have begun incorporating autism awareness training into elder care, while other regions lag behind, providing no neurodiversity-informed elderly services (Raymaker et al., 2017).

4.3. Workplace Policies and Economic Considerations
The economic implications of late diagnosis are far-reaching. Undiagnosed adults may face reduced career advancement, underemployment, or increased likelihood of early retirement due to misunderstood difficulties, thereby affecting national productivity (Buescher et al., 2014). For healthcare systems, late diagnosis often means missed opportunities for early, cost-effective interventions, resulting in more expensive mental health care later in life. Workplace policies that fail to recognize and accommodate older neurodivergent employees can lead to turnover, reduced morale, and training costs for replacements.

By contrast, implementing policies that encourage adult screening, provide accommodations, and support late-life transitions can mitigate these financial burdens. The economic case for improving late-life diagnosis and support includes reduced healthcare expenses, increased workforce participation, and improved quality of life, collectively benefiting both individuals and societies (Frazier et al., 2012).

5. Interventions, International Policy, and Economic Implications

5.1. Tailoring Interventions for Late-Diagnosed Adults
Effective interventions for older adults may differ from those for children. Therapy may emphasize understanding and accepting one’s neurodivergent profile, building upon existing coping strategies rather than starting from scratch (Belek, 2019). For ADHD, cognitive-behavioral strategies to manage executive dysfunction can be adapted for older individuals navigating retirement or changing family roles. For ASD, social skills training may focus on community engagement or communication with long-term partners and adult children.

5.2. Comparative Policy Initiatives and Global Lessons
Some European countries are pioneering inclusive policies that consider adult diagnosis and support. In the UK, the National Health Service (NHS) has recognized the need for adult autism services, though capacity remains limited (NICE, 2012/2021). In the U.S., advocacy organizations lobby for insurance coverage of adult assessments, while Canada’s public health strategies increasingly acknowledge adult ADHD. Lessons can be drawn from these efforts and adapted internationally, emphasizing training clinicians, standardizing adult screening protocols, and informing the public about late diagnosis to reduce stigma.

5.3. Economic Considerations: Cost-Benefit Analyses
Economic analyses support expanding adult diagnostic and intervention services. Studies from the UK and U.S. suggest that early identification and support for autism can reduce lifetime costs significantly (Buescher et al., 2014). While research specifically targeting late diagnosis is emerging, it stands to reason that providing timely recognition and moderate accommodations for older adults could similarly prevent costly misdiagnoses, unnecessary mental health treatments, and workforce attrition. Cross-national economic evaluations could offer insights into how investing in adult neurodiversity services might yield long-term savings and societal benefits.

6. Limitations and Directions for Future Research

Current research on late diagnosis is still developing. Many studies rely on small samples, qualitative methods, or focus heavily on ASD while underrepresenting ADHD, Dyslexia, and other neurotypes (Crane et al., 2019; Belek, 2019). Increased quantitative research is needed to determine the exact prevalence of late diagnosis in diverse regions, including Asia, Africa, and Latin America, where diagnostic infrastructures differ.

Future research should also consider socio-economic and cultural variables, examining how religious, cultural, and community norms influence the likelihood of late diagnosis and the availability of support. Moreover, longitudinal studies could investigate the outcomes of interventions tailored for older adults, measuring improvements in mental health, social engagement, employment continuity, and healthcare costs.

7. Conclusion

Late diagnosis of neurodivergence is not a rarity; it reflects evolving diagnostic frameworks, increased public awareness, and growing recognition of neurodiversity throughout life. While receiving a diagnosis in midlife or later can bring relief, self-understanding, and an opportunity to reframe past experiences, it also exposes systemic shortfalls. Healthcare services, social support networks, and workplace policies often remain ill-equipped to meet the unique needs of older neurodivergent adults.

Addressing these challenges requires comprehensive strategies: expanding clinical training to recognize late-life presentations, creating social services and housing arrangements that consider sensory and cognitive diversity, implementing inclusive workplace policies, and conducting cost-benefit analyses that demonstrate the economic advantages of supporting late-diagnosed individuals. By embracing a lifespan perspective on neurodiversity, policymakers, clinicians, researchers, and employers can enhance quality of life, reduce systemic costs, and foster a more equitable and inclusive society for all.

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