title: Empirical tests of natural selection-based evolutionary accounts of ADHD: a systematic review.
abstract: 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 natural selection-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 natural selection-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 favouring 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 symptoms of ADHD, and that their conclusions therefore lack validity for the disorder.
  
  
  CONCLUSIONS
  This review indicates that the natural selection-based accounts of ADHD have not been subjected to empirical test and therefore remain hypothetical.
authors.affiliation: 1Psychosis Research Unit,Aarhus University Hospital,Risskov,Denmark.
authors.forename: Marthe S
authors.initials: MS
authors.lastname: Thagaard
authors.affiliation: 2Departments of Psychiatry and of Neuroscience and Physiology,State University of New York (SUNY) Upstate Medical University,Syracuse,New York,USA.
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Faraone
authors.affiliation: 4Academic Unit of Psychology,University of Southampton,Southampton,UK.
authors.forename: Edmund J
authors.initials: EJ
authors.lastname: Sonuga-Barke
authors.affiliation: 1Psychosis Research Unit,Aarhus University Hospital,Risskov,Denmark.
authors.forename: Søren D
authors.initials: SD
authors.lastname: Østergaard
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000235:genetics*; D005075:Biological Evolution; D005787:Gene Frequency; D056084:Genetic Fitness; D006801:Humans; D015995:Prevalence; D050638:Receptors, Dopamine D4 / Q000235:genetics; D012641:Selection, Genetic
chemical_list: D050638:Receptors, Dopamine D4
keywords: adaptation; attention deficit disorder with hyperactivity; biological; biological evolution; genetic; selection