That said, what are the perspectives for genome-wide association studies in ADHD? The results of the first studies—though most not genome-wide significant—are already very exciting and change the way in which we think about genetic factors involved in ADHD etiology. For now, GWAS holds the greatest promise for understanding the genetic architecture of ADHD! However, we need to improve the design of these studies by increasing sample size for more power and by further improving/extending phenotypic assessment to better reflect and partition the phenotypic complexity of the disorder. The former will only become possible through collaboration. As a field, ADHD has the good fortune of having several thousand samples collected world-wide, with collaborative efforts supported by the National Institute of Mental Health. Investigators with ADHD GWAS datasets are also participating in the Psychiatric GWAS Consortium (PGC), a confederation of 101 scientists from 11 countries and 48 institutions having GWAS datasets on ADHD, autism, bipolar disorder, schizophrenia and major depression (Psychiatric GWAS Consortium Steering Committee 2009). The PGC investigators have agreed to participate in coordinated mega-analyses both within and across disorders.
