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Expert Opinion: High intelligence is inversely related to problems related to ADHD

High intelligence is inversely related to problems related to ADHD

Background

High intelligence scores have been associated with positive outcomes, such as better behavioural, cognitive and emotional control in addition to good academic performance and improved mental and physical health and mortality.1 However, several studies have found high intelligence scores and superior school performance to correlate with a predisposition towards developing bipolar disorder, psychosis and schizophrenia.2-4 For attention-deficit hyperactivity disorder (ADHD) it is argued that high intelligence is inherently related to high activity levels, low impulse control, boredom, frustration and poor attention span. Although, it has also been stated that these problems are not characteristic for ADHD as they are non-pervasive and solely specific for situations that evoke boredom and frustration. Conversely, it is hypothesized that ADHD is underdiagnosed in highly intelligent individuals as high intellect may mask ADHD problems and cognitive deficits. These opposing hypotheses have been heavily debated and not studied methodically. For this Expert Opinion article, the methodology and relevance of the first large general population based study on the relation between intelligence and ADHD problems related to ADHD will be reviewed.

Summary of abstract 

Rommelse N, Antshel K, Smeets S, et al. High intelligence and the risk of ADHD and other psychopathology. Br J Psychiatry. 2017;211(6):359-364.

 Background

High intelligence may be associated with positive (adaptive, desired) outcomes, but may also come with disadvantages.

Aims

To contribute empirically to the debate concerning whether a trade-off in IQ scores exists in relation to attention-deficit hyperactivity disorder (ADHD) and related problems, suggesting that high intelligence – like low intelligence – increases the risk of ADHD.

Method

Curves of the relation between IQ score and ADHD problems were fitted to questionnaire data (parent, teacher, self-report} in a population-based study of 2221 children and adolescents aged 10-12 years. Externalizing and internalizing problems were included for comparison purposes.

Results

Higher IQ score was most strongly related to fewer attention problems, with more rater discrepancy in the high v. average IQ range. Attention problems – but only minimally hyperactivity/impulsivity problems – predicted functional impairment at school, also in the higher IQ range.

Conclusions

Attention problems in highly intelligent children are exceptional and affect school performance; they are therefore a reason for clinical concern.

Review

The study aims to provide empirical evidence for reciprocity between high IQ scores and ADHD by utilizing the TRAILS population cohort, which has followed 2230 individuals in the northern part of the Netherlands from early adolescence into adulthood. IQ scores have been tested and ADHD related problems, such as attention problems, hyperactivity-impulsivity, externalizing problems and internalizing problems have been scored. Contrary to hypothesis, a linear inverse relation was found between IQ scores and attention problems, externalizing and – to a lesser extent – hyperactivity-impulsivity and internalizing problems.

A large unselected population-based sample, the use of multiple raters (parent, teacher and self-scoring) for problems that are related to ADHD and the use of multiple continuous IQ score measures instead of arbitrary cut-off points are among the strengths of the study. The use of multiple raters helped discern whether attention problems existed among children in multiple settings.

On the other hand, the use of only questionnaire data instead of diagnostic interview data may result in bias. Furthermore, there are several limitations concerning the reliability of the IQ scoring. Firstly, only two IQ tests were used to assess the IQ of subjects. It is argued that these IQ score estimations appeared valid, however, as they correlated strongly with school performance and socioeconomic status. Secondly, the influence of attention disorders on IQ test performance remains unknown, possibly resulting in depreciation of IQ scores in children with severe attention problems. To mitigate this, only IQ tests that did not depend on the working memory were used, which may in turn cause overvaluation of IQ scores in children with severe attention problems, although the inverse relationship between IQ score and attention problems seems to disprove this. Thirdly, children of non-Dutch parents had significantly lower IQ-scores, suggesting that language problems may influence IQ score results.

Concerning the added value of the study, doubts are raised on the relevance of the study; the article has not clearly motivated the importance of settling the debate on the association between high intelligence and the existence of ADHD and related problems. It only states that attention problems are a reason for clinical concern.

Conclusion

The discussed study is of fair methodological quality. The study population is large and unbiased, accounts for both attention problems in school and at home and uses continuous IQ score measures instead of arbitrary cut-off points. There are limitations concerning the reliability of IQ tests however, which may lead to confounding among different population characteristics. The study does not clearly motivate the relevance of settling the debate on whether high intelligence can be associated with attention problems.

D. Simons & P. Koning

References

  1. Plomin R, Deary IJ. Genetics and intelligence differences: five special findings. Molecular psychiatry. 2015;20(1):98-108.
  2. Gale CR, Batty GD, McIntosh AM, Porteous DJ, Deary IJ, Rasmussen F. Is bipolar disorder more common in highly intelligent people? A cohort study of a million men. Molecular psychiatry. 2013;18(2):190-194.
  3. Holahan CK, Holahan CJ. Being labeled as gifted, self-appraisal, and psychological well-being: a life span developmental perspective. International journal of aging & human development. 1999;48(3):161-173.
  4. Karlsson JL. Relation of mathematical ability to psychosis in Iceland. Clinical genetics. 1999;56(6):447-449.
  5. Sternberg RJ GE, Bundy DA. The predictive value of IQ. Meryll Palmer Quarterly. 2001;47:1-41.

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