The greatest risk factor for developing depression is having a parent with a mood disorder. Children of these parents are not only hereditary but also grow up in a vulnerable environment. Unfortunately, >50% of them develop depressive symptoms before their 35th birthday. The MARIO consortium – with universities, healthcare institutions, patient and other interest groups – has as its central goal to reduce this percentage. First, we create an infrastructure based on successful studies in patients with mood disorders (NESDA, BiG, OPPER). Children (12-25 years) of these patients are followed to investigate protective and risk factors for the development of depression. Secondly, we will work with patients and their children on a way to detect depressive symptoms in children early by measuring emotions and behavior (online). Third, we evaluate whether (E-health) interventions can prevent depressive symptoms in these children.