Lack of association of the dopamine transporter gene in a French ADHD sample

Discrepancies in the role of the 40 bp VNTR polymorphism of the dopamine transporter gene (DAT1) in attention‐deficit hyperactivity disorder (ADHD) could be due to various sources of genetic or phenotypical heterogeneity. We therefore analyzed a sample of 146 ADHD children and their parents, with a transmission disequilibrium test (TDT) design, assessing age, inattention, and hyperactivity dimensions and total score of the ADHD Rating Scale, the number of errors and the total score at Stroop Color‐Word test, and the total score at the Trail Making Test. The TDT for 10‐repeat (10‐R) allele shows a perfect lack of transmission bias (Mc Nemar χ2 = 0) and PBAT analyses showed no role of this polymorphism for any of the studied endophenotypes. Lack of statistical power is always a possibility, but with a sample size above the average of the majority of previous studies, and an odds ratio (number of transmitted versus untransmitted 10‐R allele) of 1.00 exactly, this possibility may be considered as not very likely. © 2008 Wiley‐Liss, Inc.