An Examination of the 2D:4D Ratio, Handedness and Footedness in Attention Deficit Hyperactivity Disorder

Abstract

Aim: Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition more common in boys than girls, although this gender variation has yet to be explained. The purpose of this study was to examine hand 2D:4D ratios and their association with ADHD. The study was also intended to compare hand 2D:4D ratios according to hand and foot dominance in individuals with ADHD. Methods: 168 children were included in the study, 91 diagnosed with ADHD and 77 healthy volunteers. All participants were evaluated via DSM-5 based psychiatric examinations, and their sociodemographic data were collected using forms prepared by the authors. The participants’ ADHD symptoms were assessed using the Conners’ Parent Rating Scale-Revised Short Form. 2D:4D ratios were determined by measuring the lengths of the bilateral second and fourth fingers using a digital compass. Hand and foot dominances were determined by evaluation in a clinical setting. The scores obtained were then compared. Results: Lower right and left hand 2D:4D ratios were determined in the individuals with ADHD than in the healthy controls (p=0.001 for both). No correlation was found between ADHD subscales and right or left hand 2D:4D ratios in the case group. No differences in 2D:4D ratios were also observed according to hand and foot dominances in the case group. Conclusion: This study produced important findings concerning whether hand 2D:4D ratios can be used as a marker of ADHD. We think that the data obtained may be of assistance to other studies assessing the phenotype characteristics of individuals with ADHD.