title: Masculinized finger-length ratios of boys, but not girls, are associated with attention-deficit/hyperactivity disorder.
abstract: Gonadal hormones may exert permanent organizational effects on sexually dimorphic finger-length ratios and sexually dimorphic behavior expressed in childhood attention deficit-hyperactivity disorder (ADHD). This study extended recent work examining associations between finger-length ratios (specifically, 2D:4D) and ADHD in a well-characterized, clinically diagnosed, community-recruited sample of boys and girls. A multistage, diagnostic procedure was utilized to identify 113 children with ADHD and 137 non-ADHD comparison children. Right-hand digit ratios showed significant mean differences by gender, as well as associations with ADHD diagnosis. Boys with ADHD had more masculinized digit ratios than control-group boys. More masculine right 2D:4D and 3D:4D ratios were correlated with parent- and teacher-rated inattentive and hyperactive-impulsive symptoms in boys but not in girls. Masculinized finger-length ratios were associated with hyperactive-impulsive and oppositional- defiant symptoms, but associations were largest with symptoms of inattention. It is concluded that prenatal, organizational effects of gonadal hormones may play a role in the development of ADHD and contribute to explaining sex differences in the prevalence rates of this childhood disorder.
authors.affiliation: Department of Psychology, Michigan State University, East Lansing 48823-1116, USA. martelmi@msu.edu
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Martel
authors.forename: Kyle L
authors.initials: KL
authors.lastname: Gobrogge
authors.forename: S Marc
authors.initials: SM
authors.lastname: Breedlove
authors.forename: Joel T
authors.initials: JT
authors.lastname: Nigg
mesh_terms: D000293:Adolescent; D000886:Anthropometry; D001289:Attention Deficit Disorder with Hyperactivity / Q000235:genetics / Q000503:physiopathology*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D005260:Female; D050278:Finger Phalanges / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D009929:Organ Size / Q000235:genetics; D012016:Reference Values; D012727:Sex Characteristics; D012733:Sex Differentiation / Q000502:physiology*; D018709:Statistics, Nonparametric