Obsessive-compulsive disorders are very damaging illnesses that can already manifest in childhood and adolescence. With an average prevalence from 1 - 3%, they are one of the most frequently diagnosed psychiatric illness in these age groups. With the further use of data, the treatment success can be significantly improved; causal variables/predictors can be recognized, understood and taken carefully into account. The anticipated incremental knowledge will ultimately help children and young people with obsessive-compulsive disorders to receive faster and more effective treatment.