Not Just a Childhood Disorder: Closing the Diagnostic Gap for Adults with ADHD

Once considered a childhood-limited condition, attention-deficit/hyperactivity disorder (ADHD) is now recognized as a chronic neurodevelopmental disorder that frequently persists into adulthood. Current estimates suggest that roughly 6% of U.S. adults meet diagnostic criteria (Staley et al., 2024), yet many remain undiagnosed or are identified years after symptom onset. Diagnostic challenges include inconsistent use of validated tools, reliance on retrospective self-report, and symptom presentations that differ from those seen in children—particularly among women, who are more likely to display inattentive features that are easily overlooked. The Clinical Assessment of Attention DeficitAdult (CAT-A; Bracken & Boatwright, 2005) addresses these gaps by integrating retrospective and current symptom scales, contextual and functional impact measures, and validity indices, offering a comprehensive framework for improving the accuracy and equity of adult ADHD assessment.

Historical Perspective

Prior to the 1960s, the focus of ADHD was largely on children, with little clinical recognition of ADHD persisting into adulthood. The Diagnostic and Statistical Manual of Mental Disorders, Second Edition (DSM-II; American Psychiatric Association, 1968) included a disorder called hyperkinetic reaction of childhood; later, the third edition (DSM-III; American Psychiatric Association, 1980) included attention deficit disorder (ADD). However, ADHD was still seen as a disorder that children would typically grow out of by adolescence or early adulthood (Weiss & Hechtman, 1993). By the early 1990s, growing clinical and research evidence began to illustrate that many individuals diagnosed with ADHD in childhood would continue to struggle with symptoms into adulthood—especially in areas related to executive functioning, emotional regulation, occupational challenges, and relationship difficulties. The fourth edition of the DSM (DSM-IV; American Psychiatric Association, 1994) retained a childhood onset requirement, but the acknowledgement of persistence into adulthood was more explicit (e.g., Barkley et al., 2002). The fifth edition of the DSM (DSM-5; American Psychiatric Association, 2013) formally updated the criteria for ADHD to be more adult-inclusive. ADHD is now understood as a chronic neurodevelopmental disorder, not just a childhood diagnosis. However, despite significant shifts in understanding ADHD in adults, diagnostic gaps remain (Moffitt et al., 2015). 

Prevalence

The National Comorbidity Survey Replication (2001–2003) estimated the prevalence of adult ADHD at 4.4% (Kessler et al., 2006), with higher rates found among males (5.4%) compared to females (3.2%; National Institute of Mental Health, n.d.). However, more recent data (Staley et al., 2024) indicated that approximately 15.5 million adults, or 6% of the adult population, have a current diagnosis. Of these, 56% received their diagnosis during adulthood.

Addressing the Diagnostic Gap

Many adults with ADHD are misdiagnosed, undiagnosed, or diagnosed years after symptom onset. In addition to the historical misconceptions already described, several other well-documented reasons exist for the underdiagnosis of ADHD in adults. 

Inadequate Use of Validated Tools

Despite the establishment of recommendations for the assessment of ADHD (e.g., National Institute for Health and Care Excellence, 2018)—which include the use of rating scales—surveys of clinicians have reported diagnostic practices that are not in line with these guidelines (Goodman et al., 2012; Knutson & O’Malley, 2010; Schneider et al., 2023). Many providers, including psychologists and physicians, do not consistently use standardized tools; most (82%) rely on unstructured clinical interviews (Schneider et al., 2023). Some practitioners (33%) report that one of the greatest challenges to diagnosing ADHD among adults is the lack of consensus regarding “gold standard” measures (Schneider et al., 2023).

However, administering self-report scales in addition to gathering collateral reports has been shown to optimize diagnostic sensitivity (Sibley et al., 2017). Using the CAT-A, a comprehensive, psychometrically sound selfreport ADHD rating scale for adults, may help providers comply with assessment guidelines. Of course, selfreport rating scales should never be used as the sole diagnostic determinant. They are an important source of data that can contribute to greater diagnostic accuracy and better treatment recommendations.  

Retrospective Symptom Reporting

Unlike a childhood ADHD diagnosis, which relies on behavioral reports from teachers and parents that are often readily available, adult ADHD diagnosis requires adults to be able to recall childhood symptoms. The CAT-A is unique in that it includes both retrospective (childhood memories) and current symptom sections, allowing clinicians to assess the developmental continuity of ADHD symptoms—an essential component of diagnosis per DSM-5 criteria (American Psychiatric Association, 2013). This dual-focus approach is particularly important for adults who may struggle to recall specific childhood behaviors asked about during an interview. By providing a structured format that allows the adult to reflect on early-life symptoms, the CAT-A supports the documentation of symptom onset prior to age 12 years while also capturing how ADHD manifests in present-day functioning.

Symptom Presentation Differences in Adults

Another challenge centers around symptom presentation: Adult ADHD symptoms often manifest differently than in children, potentially with less overt hyperactivity and more issues related to inattention and executive functioning. 

Clinicians can use the CAT-A clinical scales individually and in combination to identify the presence of symptoms that are often more commonly found in adults. These clinical scales are directly aligned to the DSM-5 criteria of Inattention, Hyperactivity, and Impulsivity.

Trends from archival CAT-A data from 2024–2025 for more than 5,300 adult respondents were recently examined. Mean scores on Inattention, Hyperactivity, and Impulsivity illustrate this common presentation, with adults reporting higher rates of inattention when compared to impulsivity and hyperactivity—even those with CAT-A clinical index scores in Very Significant Clinical Risk range (see Table 1).

Sex Biases

Sex plays a significant role in the underdiagnosis, misdiagnosis, and delayed diagnosis of ADHD in adults. These biases shape both how symptoms are expressed and how they are interpreted by clinicians, often leading to disparities in identification and treatment. As mentioned earlier, approximately 6% of adults in the U.S. have a current ADHD diagnosis, with males diagnosed at a higher rate than females (National Institute of Mental Health, n.d.; Staley et al., 2023).

Inattentive symptoms, which are more common in females, are less disruptive and less likely to draw attention in school or clinical settings. Similar results were found in the CAT-A archival data, wherein females had significantly higher scores on the Current Symptoms and Childhood Memories Inattention scales when compared to males. Females (M = 69.91, SD = 11.31) scored significantly higher than males (M = 67.34, SD = 12.39) on the Current Symptoms Inattention scale (t[5322] = 6.822, p < .001) and on the Childhood Memories Inattention scale (females M = 66.87, SD =11.41, males M = 62.90, SD = 12.12, t(5322) = 11.983,  p < .001). Madhoo and Quinn (2014) found that women are more likely than men to be diagnosed later in life and are more frequently misdiagnosed with mood disorders. Women with ADHD tend to internalize their struggles, leading to chronic feelings of shame, burnout, and low self-esteem. These emotional consequences may mask core ADHD symptoms and lead clinicians to focus on emotional distress rather than attentional dysfunction. Social expectations often pressure women to overcompensate through perfectionism or high emotional intelligence, which can temporarily hide ADHD symptoms. Masking may be mistaken for successful coping, delaying or preventing diagnosis.

Lack of Contextual Evaluation

Standard assessments may not adequately consider the individual’s functioning across various settings, such as work, home, and social environments, which is crucial for an accurate diagnosis. The CAT-A offers insights across context clusters (Personal, Academic/Occupational, Social) and locus clusters (Internal and External). This multidimensional approach allows clinicians to better understand the functional impact of ADHD across environments and the distinction between internal struggles (e.g., racing thoughts, emotional restlessness) and external symptoms (e.g., fidgeting, interrupting). These distinctions are often critical in adult evaluations, wherein outward hyperactivity may have diminished but internal symptoms remain impairing.

Data on the differences between a sample of individuals who were not suspected to have ADHD (CAT-A clinical index score < 65) and a sample of individuals with suspected ADHD (CAT-A clinical index score > 65) from the archival CAT-A dataset illustrate the utility of the context clusters and locus clusters (see Table 2).

Response Distortion

The CAT-A also addresses a common barrier in adult ADHD assessment: response distortion. Many adults underreport or exaggerate symptoms based on self-perception, stigma, or secondary gain. The CAT-A’s embedded validity scales (Negative Impression, Positive Impression, and Infrequency) help flag inconsistent or biased responses, enhancing the accuracy and interpretability of the results.

• Negative Impression (NI): Detects potential exaggeration of symptoms or negative response bias.
• Infrequency (IF): Identifies atypical or inconsistent response patterns that may indicate random answering or misunderstanding of items.
• Positive Impression (PI): Assesses the tendency to underreport symptoms or present oneself in an overly favorable light.

These scales help clinicians evaluate the credibility of the self-reported data and identify any potential response biases.

As shown in Table 3, individuals in the archival sample with suspected ADHD (CAT-A clinical index score > 65) tended to have an increased prevalence of scores in the atypical and very atypical ranges on the Negative Impression and Infrequency scales compared to individuals in the CAT-A normative sample. 

Furthermore, the CAT-A’s alignment with DSM-5 diagnostic criteria (American Psychiatric Association, 2013)—alongside strong psychometric properties, including high internal consistency and representative normative data—ensures that clinicians have access to a developmentally informed, standardized, and diagnostically relevant tool. It serves as clinical tool for assessing ADHD in adults, supporting diagnostic accuracy, guiding treatment planning, and enabling longitudinal tracking of symptoms and functional impairments across personal, academic/occupational, and social contexts.

Summary

The CAT-A directly addresses the core challenges that have historically contributed to gaps in adult ADHD diagnosis: inadequate childhood history, variability in adult symptom expression, under-recognition of internalizing symptoms, and concerns about response validity. Its structure and content make it an important addition to the clinician’s toolbox when working with adult populations at risk for overlooked or misunderstood ADHD presentations.

References

American Psychiatric Association (1968). Diagnostic and statistical manual of mental disorders (2nd ed.). Author. 

American Psychiatric Association (1980). Diagnostic and statistical manual of mental disorders (3rd ed.). Author. 

American Psychiatric Association (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Author. 

American Psychiatric Association (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Author. 

Barkley, R. A., Fischer, M., Smallish, L., & Fletcher, K. (2002). The persistence of attention‐deficit/hyperactivity disorder into young adulthood as a function of reporting source and definition of disorder. Journal of Abnormal Psychology, 111(2), 279–289. https://psycnet.apa.org/doi/10.1037/0021843X.111.2.279 

Bracken, B. A., & Boatwright, B. S. (2005). Clinical Assessment of Attention Deficit–Child (CAT-C)/Clinical Assessment of Attention Deficit–Adult (CAT-A): Professional manual. PAR.

Goodman, D. W., Surman, C. B., Scherer, P. B., Salinas, G. D., & Brown, J. J. (2012). Assessment of physician practices in adult attention-deficit/hyperactivity disorder. The Primary Care Companion for CNS Disorders, 14(4), PCC.11m01312. https://doi.org/10.4088/PCC.11m01312 

Kessler, R. C., Adler, L., Barkley, R., Biederman, J., Conners, C. K., Demler, O., Faraone, S. V., Greenhill, L. L., Howes, M. J., Secnik, K., Spencer, T., Ustun, T. B., Walters, E. E., & Zaslavsky, A. M. (2006). The prevalence and correlates of adult ADHD in the United States: results from the National Comorbidity Survey Replication. American Journal of Psychiatry, 163(4), 716–723. https://doi.org/10.1176/ ajp.2006.163.4.716 

Knutson, K. C., & O’Malley, M. (2010). Adult attention-deficit/ hyperactivity disorder: A survey of diagnosis and treatment practices. Journal of the American Academy of Nurse Practitioners, 22(11), 593–601. https://doi.org/10.1111/j.17457599.2010.00546.x 

Madhoo, M., & Quinn, P. O. (2014). A review of attention-deficit/ hyperactivity disorder in women and girls: Uncovering this hidden diagnosis. The Primary Care Companion for CNS Disorders, 16(3), PCC.13r01596. https://doi.org/10.4088/ pcc.13r01596  

Moffitt, T. E., Houts, R., Asherson, P., Belsky, D. W., Corcoran, D. L., Hammerle, M., Harrington, H., Hogan, S., Meier, M. H., Polanczyk, G. V., Poulton, R., Ramrakha, S., Sugden, K., Williams, B., Rohde, L. A., & Caspi, A. (2015). Is adult ADHD a childhood-onset neurodevelopmental disorder? Evidence from a four-decade longitudinal cohort study. American Journal of Psychiatry, 172(10), 967–977. https:// doi.org/10.1176/appi.ajp.2015.14101266 

National Institute of Mental Health. (n.d.). Attention-deficit/ hyperactivity disorder (ADHD). U.S. Department of Health and Human Services, National Institutes of Health. https:// www.nimh.nih.gov/health/statistics/attention-deficithyperactivity-disorder-adhd

National Institute for Health and Care Excellence. (2018). Attention deficit hyperactivity disorder: Diagnosis and management [NICE Guideline NG87]. https://www.nice. org.uk/guidance/ng87

Schneider, B. C., Schöttle, D., Hottenrott, B., Gallinat, J., & Moritz, S. (2023). Assessment of adult ADHD in clinical practice: Four letters—40 opinions. Journal of Attention Disorders, 27(9), 1051–1061. https://doi. org/10.1177/1087054719879498

Sibley, M. H., Swanson, J. M., Arnold, L. E., Hechtman, L. T., Owens, E. B., Stehli, A., Abikoff, H., Hinshaw, S. P., Molina, B. S. G., Mitchell, J. T., Jensen, P. S., Howard, A. L., Lakes, K. D., & Pelham, W. E., for the MTA Cooperative Group. (2017). Defining ADHD symptom persistence in adulthood: Optimizing sensitivity and specificity. Journal of Child Psychology and Psychiatry, 58(6), 655–662. https://doi. org/10.1111/jcpp.12620 

Staley, B. S., Robinson, L. R., Claussen, A. H., Katz, S. M., Danielson, M. L., Summers, A. D., Farr, S. L., Blumberg, S. J., & Tinker, S. C. (2024). Attention-deficit/hyperactivity disorder diagnosis, treatment, and telehealth use in adults—National Center for Health Statistics Rapid Surveys System, United States, October–November 2023. Morbidity and Mortality Weekly Report, 73(40), 890–895. https://doi. org/10.15585/mmwr.mm7340a1

Weiss, G., & Hechtman, L. T. (1993). Hyperactive children grown up: ADHD in children, adolescents, and adults (2nd ed.). Guilford Press.