In the United States (U.S.), attention‐deficit/hyperactivity disorder (ADHD) is one of the most prevalent neurodevelopmental disorders diagnosed in childhood (
1). The 2016
National Survey of Children's Health (NSCH) estimated that 8.4% of children aged 2–17 had a current ADHD diagnosis (
2). More recent NSCH data from 2022 suggests that 10.5% (∼6.5 million) of U.S. children are currently diagnosed with ADHD (
3). Although ADHD was originally conceptualized as a childhood disorder, extant literature suggests symptoms often endure into adulthood (
4). Current prevalence estimates for persistent adult ADHD range from 2.5% (∼139 million) to 6.7% (∼366 million) worldwide (
5). Increasing prevalence estimates across time may be due to a growing awareness of ADHD through the use of social media platforms (which can lead to over‐evaluation through the sharing of [oftentimes] misleading information), increased efforts to seek care for ADHD, and/or heightened levels of mental health challenges during the COVID‐19 pandemic (
6,
7,
8).
ADHD prevalence rates vary by several demographic factors, including sex, socioeconomic status, geographic region, and race/ethnicity (
2,
9,
10,
11). Notably, ADHD diagnosis is more prevalent among non‐Hispanic White children and adults compared to racially/ethnically minoritized individuals (
12,
13,
14,
15). However, these differential prevalence rates largely reflect racial and ethnic health disparities in both the diagnosis and treatment of ADHD (
12,
15,
16). Both structural and attitudinal barriers to treatment (i.e., socio‐economic status and access to healthcare resources, trust in the medical system, general healthcare utilization) likely explain why non‐Hispanic White children and adults are overtreated/over‐diagnosed with ADHD while racially/ethnically minoritized groups are undertreated/underdiagnosed (
12,
17,
18).
Interestingly, although disparities in ADHD diagnosis are well documented among minoritized individuals, relatively little research has examined for other differences, particularly neurocognitive test performance and co‐occurring psychopathology. Outside of ADHD populations, research has shown significant group differences in neuropsychological test performance between adult non‐Hispanic White and racial/ethnic minorities in the U.S. compared to non‐Hispanic White adults on tests of language, visuoconstruction, attention, nonverbal processing speed, and executive functioning (
19,
20,
21). Additionally, significant differences in psychological symptom (e.g., depressive symptoms) reporting are present across racial/ethnic groups in adults, with minority individuals often reporting higher levels of psychological distress (
22,
23). Despite these findings, few studies have examined potential differences in either neurocognitive performance or psychological symptoms among adults with ADHD from diverse ethnic groups. This lack of clarity is concerning given the rise of ADHD prevalence in the U.S. and the present healthcare disparities experienced by racial/ethnic minority groups.
Future research is warranted to delineate race‐based differences in neurocognitive test performance and psychological symptom reporting among adults with ADHD. Assessing group differences may aid clinicians by reducing diagnostic errors and improving treatment outcomes for underserved patients with ADHD (
24). This study was designed to expand upon the limited representation of racial/ethnic minorities in neuropsychological research by investigating race‐based disparities in neurocognitive test performance and psychiatric/ADHD symptom reporting among groups in a demographically diverse sample.
METHODS
Participants
Data from 913 consecutive adults referred for neuropsychological evaluation at an academic medical center psychiatry department for ADHD diagnostic clarification or treatment planning related to established ADHD were analyzed. All patients received a comprehensive diagnostic evaluation, which included record review, detailed patient history questionnaire, clinical interview, self‐report measures of ADHD and psychological symptomology, and a focused neuropsychological test battery (see Measures below). Study exclusion criteria were: (1) no ADHD diagnosis following evaluation; (2) evidence of invalid test performance on objective performance validity tests (PVTs); (3) “other” patient‐identified race/ethnicity (i.e., biracial/multiracial, non‐Black, ‐Hispanic, ‐Asian, ‐White); and/or (4) below average estimated IQ (i.e., <90) based on the test of premorbid functioning (TOPF; (
25)). Following application of exclusion criteria, the final sample consisted of 491 patients with a mean age of 28.62 (SD = 7.16) and education of 16.10 years (SD = 2.12). The sample was 42% male/58% female with the following patient‐identified racial/ethnic breakdown: 51% White (
n = 252), 22% Hispanic (
n = 110), 15% Black (
n = 74), and 11% Asian (
n = 55). Notably, all patients identified English as their primary language and 30% (
n = 148) of the total sample identified as bi‐lingual (White = 12%; Hispanic = 75%; Black = 14%; Asian = 59%). Additionally, of the entire sample, 4% (
n = 18) had a history of comorbid learning disability, of which the demographic breakdown was as follows: White 4% (
n = 10); Hispanic 6% (
n = 7); Black 1% (
n = 1); Asian 0%.
Measures
Neuropsychological Test Battery
The battery consisted of the following tests: TOPF, Rey Auditory Verbal Learning Test (RAVLT; unstructured verbal learning and memory), Weschler Adult Intelligence Scale‐Fourth Edition (WAIS‐IV) Digit Span (DS; working memory), Letter‐Number Sequencing (LN; working memory), Coding (CD; processing speed), and Symbol Search (SS; processing speed) subtests, Trail Making Test Parts A & B (TMT‐A, psychomotor processing speed/sequencing; TMT‐B; mental flexibility and set‐shifting), and Stroop Color and Word Test (SCWT; Inhibition Trial; response inhibition). As part of this battery, two freestanding (Dot Counting Test (
26) and Rey‐15 item and Recognition (
27)) and two embedded (RAVLT Effort Score (
28) and Stroop Word Reading T‐score (
29)) PVTs were examined. Those with ≥2 failures were excluded for performance invalidity.
ADHD/Psychological Symptom Measures
The Clinical Assessment of Attention Deficit‐Adult (CAT‐A; (
30)) is a 108‐item measure in which examinees self‐rate key ADHD symptoms of inattention, impulsivity, and hyperactivity in both childhood and currently. For this study, the childhood, current, and overall clinical index scores were examined. The Beck Depression Inventory‐Second Edition (BDI‐II; (
31)) and Beck Anxiety Inventory (BAI; (
32)) were used to assess severity of depressive mood symptoms and anxiety symptoms, respectively.
Data Analysis
The sample was dichotomized into average (90–109;
n = 174) and above average (≥110;
n = 317) IQ groups based on TOPF‐estimated FSIQ. This was done due to IQ's influence on ADHD outcomes and evidence for greater performance on neuropsychological tests compared those with average IQ or below (
33,
34). The TOPF‐estimated IQ has been shown to correlate highly with WAIS‐IV FSIQ (
35). Analyses of variance (ANOVAs) assessed for significant group differences in demographic variables (i.e., age, education), objective neurocognitive test performance, or self‐reported depression, anxiety, and ADHD symptoms based on patient‐identified race/ethnicity (i.e., White, Black, Hispanic, Asian). The false discovery rate (FDR) procedure controlled the familywise error rate associated with multiple comparisons with a 0.05 maximum FDR (
36).
RESULTS
Groups were well‐matched across age and education among the average and above average IQ groups (
Table 1). For the average IQ group, ANOVAs assessing mean differences between race and neurocognitive performance were nonsignificant, aside from Digit Span, with medium effect size. No differences emerged among self‐reported depression, anxiety, or ADHD symptoms. ANOVAs for the above average IQ group found no significant differences for any of the neurocognitive or psychiatric measures. These findings demonstrate comparable neurocognitive test performance and ADHD and psychiatric symptom endorsement across racial groups undergoing neuropsychological evaluation for ADHD.
DISCUSSION
Overall, findings from the present study demonstrated nonsignificant differences between participants of different racial/ethnic groups with regard to neuropsychological test performance and psychological symptom reporting. Specifically, outside of Hispanic patients performing significantly lower on Digit Span, which is a previously documented phenomenon (
37), there were nonsignificant differences in verbal learning and delayed recall, processing speed, and executive functioning scores between participants who identified as non‐Hispanic White, non‐Hispanic Black, Hispanic, or Asian in both the Average and Above Average IQ groups.
Although disparities in the diagnosis and treatment of ADHD based on race/ethnicity have been well documented (e.g., (
18)), there is less clarity on potential differences in neuropsychological functioning and symptom presentation across racial/ethnic groups, particularly in adult populations. For example, there is evidence that cultural differences such as parenting styles may influence ADHD symptom presentation (
38). Notably, although prior research has demonstrated performance differences on neuropsychological tests between non‐Hispanic White adults and non‐White counterparts across various populations (
19,
21) and less psychological distress reported by non‐Hispanic Whites compared to other racial groups (
22,
23), neither of these have been well‐studied among adults with ADHD. Based on the current findings, there is generally parity in neuropsychological test performance and psychological symptom reporting across individuals of various racial/ethnic backgrounds, when stratified by IQ. While differences emerged on an isolated measure of attention/working memory, scores remained average across groups. Working memory abilities in children have been associated with parental sociodemographic status, which may partly account for disparities maintained throughout adulthood (
39). The replicability of this finding, along with potential moderating variables should be examined in future studies.
This study benefited from several methodological strengths, including a large sample, a neuropsychological test battery that allowed for comparison of performance differences across multiple domains of neurocognitive functioning (e.g., attention/working memory, learning/memory, processing speed, executive functions), and inclusion of multiple PVTs. That said, some limitations warrant notation. The sample was largely composed of undergraduate and graduate/professional students undergoing ADHD evaluation. Consequently, mean education of the sample was higher than the general population average, and findings may not necessarily generalize to broader, community‐dwelling populations. Relatedly, although the sample had a wide range of IQ, there was insufficient data for those with IQs <90 for statistical analysis. Thus, it remains unclear if current findings would replicate among those with below average baseline intellectual function. Finally, some of the subgroup sample sizes were modest, such that replication with larger subgroup sizes and among those who identify as other ethnoracial identities would be beneficial.
ADHD is one of the most prevalent neurodevelopmental disorders in the U.S., though many facets of this disorder remain understudied among adults, especially among adults from minoritized populations. Current results showed largely nonsignificant differences in neuropsychological test performance, ADHD symptom reporting, and active affective psychopathology symptoms between non‐Hispanic White, non‐Hispanic Black, Hispanic, and Asian adults with ADHD referred for clinical neuropsychological evaluation. As such, although prior research has consistently documented racial/ethnic disparities in rates of ADHD diagnosis (primarily among children), current results did not demonstrate neuropsychological performance‐based differences apart from working memory performance among young adults diagnosed with ADHD.