An evidenced-based perspective on the validity of attention-deficit/hyperactivity disorder in the context of high intelligence
Section snippets
Background
Despite the fact that ADHD occurs in 6–8% of children and 2–3% of adults (Simon et al., 2009, Thomas et al., 2015) and high intelligence only in 2–5% of the population depending on the definition/cut-off, it is vigorously debated whether or not the combination of both occurs more often than expected by chance. Intelligence is a well-researched topic in ADHD literature. Meta-analyses suggest that, compared with controls, IQ is nine points lower in pediatric populations with ADHD (Frazier et al.,
Methods
The current systematic review of available literature regarding the association between high intelligence and behavioral traits of ADHD (or closely associated features) was organized according to the sample ascertainment source: (1) population based, (2) gifted programs/school nominations/associations for giftedness, or (3) clinically referred for a psychiatric evaluation. Initially, the core symptoms of ADHD were considered (attention, impulsivity, hyperactivity). Thereafter, associated
Methodological issues
A primary methodological issue is the large discrepancies that exist in the operationalization of high intelligence. Cut-off-scores for high intelligence ranged from ≥1 SD (IQ ≥ 115) to ≥3 SD (IQ ≥ 145). In other words, the upper 16% to 0.1% of the population were considered both as having high intelligence. A second methodological issue is that studies differed substantially in ascertainment methods. Population studies including a representative group of highly intelligent students (i.e., based on
Discussion
We set out to systematically review the available literature, hoping to answer a set of questions to determine the validity of an ADHD diagnosis in the context of high intelligence. We hypothesized that if high intelligence mimics the symptoms of ADHD in the absence of the specific pathophysiological pathways for ADHD and their correlates, that persons with high intelligence and ADHD symptoms (1) would demonstrate less functional impairment, (2) would have a more favourable course, (3) would
Research agenda
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Urgently needed are large longitudinal population/twin based cohort studies that incorporate validated assessments of ADHD symptoms and intelligence addressing the following research topics:
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How prevalent and persistent are ADHD symptoms in children with high intelligence compared to average intelligent children?
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How prevalent and persistent are ADHD symptoms in children with high intelligence enrolled in gifted education classes compared to children with high intelligence enrolled in general
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Clinical recommendations
Given the lack of relevant, high quality studies, only clinical suggestions rather than conclusive statements can be made. First, the main clinical recommendation is that clinicians should feel comfortable applying standard diagnostic criteria for ADHD to high IQ individuals. When diagnosing ADHD in individuals with a high IQ, data about symptoms can be elicited in the usual manner. However, the main clinical challenge is defining impairment. In many clinical contexts, impairment may be defined
Financial disclosure/Acknowledgements
Nanda Rommelse, Marieke van der Kruijs, Jochem Damhuis, Kevin Antshel, Ineke Hoek, Lianne Hoogeveen and Stijn Smeets reported no biomedical financial interests or potential conflicts of interest. In the past year, Dr. Faraone received income, potential income, travel expenses and/or research support from Arbor, Pfizer, Ironshore, Shire, Akili Interactive Labs, CogCubed, Alcobra, VAYA Pharma, Neurovance, Impax, NeuroLifeSciences. With his institution, he has US patent US20130217707 A1 for the
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