Testing the evolutionary advantage theory of attention-deficit/hyperactivity disorder traits.

Abstract

To reconcile the strong secular persistence of attention-deficit/hyperactivity disorder (ADHD) despite its impairing effects, ADHD traits have been postulated to offer an evolutionary advantage. It has been proposed that such advantages should in particular be observable under time-critical, novel, and resource-depleted conditions requiring response-readiness and high levels of scanning and exploration/foraging. Our objective was to provide the first behavioral test of this hypothesis. Schoolchildren from the general population with no/few (n = 56), mild (n = 50), moderate (n = 48), and severe (n = 48) ADHD traits, defined according to their ADHD-Rating Scale IV (ADHD-RS-IV) total score, participated in an exploratory foraging and response-readiness laboratory test. Here, children searched for coins hidden in locations of varying obscurity in an unfamiliar room for 1min. Test-performance (number of coins found) adjusted for age, sex, and estimated IQ was analyzed categorically using multiple linear regression analyses and dimensionally by fitting a regression model including the ADHD-RS-IV score as a continuous measure. There were no differences in the mean number of coins between the No/Few (Mean = 7.82), Mild (Mean = 7.76), Moderate (Mean = 7.58), and Severe (Mean = 7.88) groups [F(3,195) = 0.24, p = 0.871]. Furthermore, excluding children with functional impairment, adjusting for verbal working memory and response inhibition, and stratifying for sex did not change these findings. Finally, continuous ADHD traits were not found to be related to test-performance [F(3,195) = 0.73, p = 0.536]. While our results do generally not support the evolutionary advantage theory (i.e., ADHD traits neither conferred an advantage nor a disadvantage), this does not disprove that ADHD traits may have offered advantages via other mechanisms.