A Genome-Wide Association Meta-Analysis of Attention-Deficit/Hyperactivity Disorder Symptoms in Population-Based Pediatric Cohorts.

Objective: The aims of this study were to elucidate the influence of common genetic variants on childhood attention-deficit/hyperactivity disorder (ADHD) symptoms, to identify genetic variants that explain its high heritability, and to investigate the genetic overlap of ADHD symptom scores with ADHD diagnosis.
Method: Within the EArly Genetics and Lifecourse Epidemiology (EAGLE) consortium, genome-wide single nucleotide polymorphisms (SNPs) and ADHD symptom scores were available for 17,666 children (<13 years of age) from nine population-based cohorts. SNP-based heritability was estimated in data from the three largest cohorts. Meta-analysis based on genome-wide association (GWA) analyses with SNPs was followed by gene-based association tests, and the overlap in results with a meta-analysis in the Psychiatric Genomics Consortium (PGC) case-control ADHD study was investigated.
Results: SNP-based heritability ranged from 5% to 34%, indicating that variation in common genetic variants influences ADHD symptom scores. The meta-analysis did not detect genome-wide significant SNPs, but three genes, lying close to each other with SNPs in high linkage disequilibrium (LD), showed a gene-wide significant association (p values between 1.46 × 10(-6) and 2.66 × 10(-6)). One gene, WASL, is involved in neuronal development. Both SNP- and gene-based analyses indicated overlap with the PGC meta-analysis results with the genetic correlation estimated at 0.96.
Conclusion: The SNP-based heritability for ADHD symptom scores indicates a polygenic architecture, and genes involved in neurite outgrowth are possibly involved. Continuous and dichotomous measures of ADHD appear to assess a genetically common phenotype. A next step is to combine data from population-based and case-control cohorts in genetic association studies to increase sample size and to improve statistical power for identifying genetic variants.
Competing Interests: Dr. Hudziak has received grant or research support from the National Institutes of Health, the National Institute of Mental Health, the National Institute of Diabetes and Digestive and Kidney Disease, and the state of Vermont. His primary appointment is with the University of Vermont. He has additional appointments with Erasmus University in Rotterdam, Netherlands, Washington University School of Medicine in St. Louis, Missouri, and the Geisel School of Medicine at Dartmouth in Hanover, New Hampshire. Drs. Middeldorp, Groen-Blokhuis, St Pourcain, Greven, Pappa, Tiesler, Nolte, Ebejer, Zhao, Davies, Ehli, Evans, Guxens, Hottenga, Jugessur, Kemp, Martin, Myhre, Ormel, Ring, Standl, Stergiakouli, Stoltenberg, Thiering, Timpson, Trzaskowski, van der Most, Nyholt, Medland, Neale, Jacobsson, Sunyer, Hartman, Whitehouse, Pennell, Heinrich, Plomin, Smith, Tiemeier, Posthuma, Boomsma, Ms. Hammerschlag, Mr. Ouwens, Mr. Ang, Ms. Vilor-Tejedor, Mr. Bacelis, Ms. Fedko, Ms. Krapohl, Mr. Murcia, and Ms. Wang report no biomedical financial interests or potential conflicts of interest.
(Copyright © 2016 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.)