This study has a naturalistic design. The aim is to map all new treatments with ADHD drugs at all 13 public BUP units in Stockholm County and one BUP unit on Gotland. The participation means that medication is initiated as planned in normal clinical practice by the child´s ordinary physician, and beyond this only means a somewhat denser and more structured follow-up. In addition, the investigators will ask for saliva samples from the patient and his/her parents. The investigators aim at including at least 1000 individuals in total in the study.