"Attention deficit hyperactivity disorder (ADHD) is one of the most common and most heritable childhood onset psychiatric conditions. At the same time, genetics of ADHD are largely unknown and increasingly controversial. So far, the genetic risks implicated in ADHD generally tend to have small effect sizes or be rare, or often refer to co-occurring psychopathologies. Thus, there is a growing need for projects pursuing approaches alternative to association studies that have been dominating the field of ADHD genetics in recent years. Motivated by this issue, we propose to examine the epigenetic effects in ADHD. The object is to evaluate imprinting and methylation patterns in ADHD cases and controls. The proposed project aims to utilize methods that complement conventional genetic association studies and have a starting point not limited to hypotheses of specific candidate genes. Imprinting will be analyzed by log-linear regression method, while Illumina Human Methylation 450K chip will be applied to obtain methylation patterns. We will exploit the data of such large cohorts as ALSPAC and Norwegian mother-child study. The assessment of determined epigenetic candidate genes will extend to additional four satellite projects in collaboration with our: (1) clinical group (epigenetics and perinatal factors), (2) neurotargeting group (epigenetics in cell lines), (3) statistical genetics group (epigenome x genome interaction) and (4) animal studies group (epigenetics and stress). The proposal will not only shed light on etiology of ADHD, but also unite several European research groups (Germany, Netherlands, Spain, Norway and UK) as well as create a bridge between the Academia and a private research sector at the University of Bergen (K.G.Jebsen neuropsychiatric center)."