Empirical tests of natural selection-based evolutionary accounts of ADHD: a systematic review

Abstract

(248 words)Objective: ADHD is a prevalent and highly heritable mental disorder associated with significant impairment, morbidity and increased rates of mortality. This combination of high prevalence and high morbidity/mortality seen in ADHD and other mental disorders presents a challenge to naturalselection-based models of human evolution. Several hypotheses have been proposed in an attempt to resolve this apparent paradox. The aim of this study was to review the evidence for these hypotheses. Methods:We conducted a systematic review of the literature on empirical investigations of naturalselection-based evolutionary accounts for ADHD in adherence with the PRISMA guideline. The PubMed, Embase, and PsycINFO databases were screened for relevant publications, by combining search terms covering evolution/selection with search terms covering ADHD. Results:The search identified 790 records. Of these, 15 full-text articles were assessed for eligibility, and three were included in the review. Two of these reported on the evolution of the seven-repeat allele of the ADHD-associated dopamine receptor D4 gene, and one reported on the results of a simulation study of the effect of suggested ADHD-traits on group survival. The authors of the three studies interpreted their findings as favoring the notion that ADHD-traits may have been associated with increased fitness during human evolution. However, we argue that none of the three studies really tap into the core ADHD phenotype, and that their conclusions therefore lack validity for ADHD. Conclusions:This review indicates that the natural-selection-based hypotheses for ADHD have not been subjected to empirical test and therefore remain entirely speculative. Keywords:Attention Deficit Disorder with Hyperactivity; Biological Evolution; Selection, genetic; Adaptation, Biological. 3 Summations-The search conducted for our systematic review of empirical investigations of natural-selectionbased evolutionary accounts for ADHD identified 790 records. Of these, 15 full-text articles were assessed for eligibility, and only three were included in the review.-The authors of the three studies included in this review interpreted their findings as favoring the notion that ADHD-traits may have been associated with increased fitness during human evolution. However, we argue that none of the three studies really tap into the core ADHD phenotype, and that their conclusions therefore lack validity for ADHD.-This review indicates that the natural-selection-based hypotheses for ADHD have not been subjected to empirical test and therefore remain entirely speculative. We suggest that this gap in knowledge should be addressed in future studies. Considerations-Publications relevant for this topic may have gone undetected in our search.-It is noteworthy that there are more publications raising hypotheses for the evolutionary background for ADHD than there are studies testing them empirically.

Genetics in the ADHD Clinic: How Can Genetic Testing Support the Current Clinical Practice?

“…One explanation for this – also known as the mismatch theory ( Crawford and Salmon, 2002 ; Durisko et al, 2016 ) or the anachronism of ADHD ( Arcos-Burgos and Acosta, 2007 ) – could be that changes in human societies have occurred so rapidly that they have outpaced the much slower evolutionary changes required to select for these traits ( Jensen et al, 1997 ). Another potential approach is the natural positive selection theory ( Thagaard et al, 2016 ), which suggests that ADHD traits may have been beneficial in certain circumstances. For example, in a hunter-gatherer environment which is typically characterized by the depletion of resources, and also time-critical and novel-rapidly changing conditions, hyperactivity could have been advantageous in spotting new opportunities or migrating toward better climates, whereas impulsivity as related to the response-readiness and the ability to fight-or-flee, and inattention, as a high-scanning behavior could have likely been adaptive under these environmental conditions ( Jensen et al, 1997 ).…”

The Relationship of Personality Style and Attention Deficit Hyperactivity Disorder in Children

“… 6 , 10 However, others have argued the constructs associated with ADHD may be adaptive and represent a positive adjustment to a disorganized and chaotic world. 11 , 12 …”

Genomic analysis of the natural history of attention-deficit/hyperactivity disorder using Neanderthal and ancient Homo sapiens samples

“…The fact that ADHD poses such a burden on individual life quality 9 and yet is so prevalent seems counterintuitive from an evolutionary perspective, as one might expect natural selection to purge the risk alleles from the population 10 . In this regard, several hypotheses have been put forward to explain the evolutionary persistence of this disorder, each of them emphasising on different aspects of the ADHD phenotype (Table 1).…”

“…Overall, mismatch-related hypotheses in ADHD have been speculative 9 , but current genomic data allows to assess the evidence supporting each proposed model. Here we study the evolutionary nature of ADHD from a genomic perspective by analysing traces of selection in AMH and assessing the role that archaic interbreeding played in the genetic variation associated with this trait.…”