Family based association analysis of statistically derived quantitative traits for drug use in ADHD and the dopamine transporter gene

Abstract

Objective To determine whether SNPs within the dopamine transporter gene (DAT) are associated with quantitative phenotypes generated from drug frequency variables in an ADHD sample.

Method 35 SNPs were genotyped in and around DAT. We developed a quantitative phenotype at each SNP by weighting the drug frequency variables. The weights were selected to maximize the heritability at each SNP. Once a quantitative phenotype was generated at each SNP, a screening procedure was used to select and test the SNPs with the greatest power to detect an association in DAT.

Results No SNPs in DAT were associated with the quantitative phenotypes generated from the drug frequency variables after the multiple comparisons adjustment; however, some SNPs achieved nominal significance. A sliding window of analysis of 3 SNPs also resulted in only nominal associations.

Conclusions SNPs in DAT do not appear to be associated with the phenotypes generated from drug frequency variables among individuals with ADHD.