Mood disorders in children and adolescents are a serious global problem for the health care field and society. Stress hormones cortisol and aldosterone are thought to be involved in the pathophysiology of depressive disorders. There is evidence that the supplementation of omega-3 fatty acids can be helpful in the prevention and treatment of these disorders. This study examines the effects of supplementation with omega-3 fatty acids on cortisol and aldosterone concentrations in saliva obtained in the sample of children described previously. The study group involves boys and girls between the age of 7 and 18 years suffering from either mixed anxiety and depressive disorder or depressive disorder. Patients were randomly divided into two groups to receive either omega-3 fatty acids (referred to as the Om3 group) or omega-6 fatty acids as an active comparator (referred to as the Om6 control group) in addition to their antidepressant therapy. As a source of omega-3 fatty acids, a fish oil emulsion was used. A sunflower oil was used as a source for omega-6. Patients in both groups received 20 ml of oil daily for 12 weeks. Six saliva samples were collected from each patient. Sampling took place in the morning and at midday at three specific time intervals, namely at the beginning of the study (Week 0), at the middle of the intervention with fatty acids (Week 6), and at the end of the intervention with fatty acids (Week 12). Cortisol and aldosterone concentrations will be measured using ELISA and our own methodology. [ABSTRACT FROM AUTHOR]