Effect of Quetiapine on Brain Activity Patterns in Patients With Heightened Risk of Bipolar Disorder

Inclusion Criteria: * diagnosis of depressive episode (F32.X, F33.X) with duration less than \< 6 months * max. three previous episodes of illness * no manic or hypomanic episodes in the past * current treatment with one antidepressant * MRI-compatibility * unequivocal understanding of study information and autonomous consent * for women: negative pregnancy test * for risk-group: * 14 or more points on hypomania checklist (HCL-32) * additionally at least one of the following four risk factors: 1. positive family history (i.e. first or second order relatives with BPD, schizoaffective or schizophrenic psychosis, mania or suicide attempt) 2. initial manifestation before 30 years of age 3. initial manifestation after childbirth 4. suicide attempt in the past Exclusion Criteria: * additional diagnoses of psychiatric disorders (Organic, including symptomatic, mental disorders \[F0X.X\]; mental and behavioural disorders due to psychoactive substance use \[F1X.X\]; schizophrenia, schizotypal and delusional disorders \[F2X.X\]; mental retardation \[F7X.X\]) * chronic or acute physical disease * individuals who are in a dependence- or work-relation with the sponsor * limited or annulled legal capacity * court or administrative order for hospitalisation * for women: pregnancy, nursing period or unsafe contraceptive methods * for the risk group: * clinical relevant changes in clinical chemistry, hematology, EEG or EKG * known contraindication for quetiapine (e.g. hypersensitivity to \[active\] ingredient\[s\], HIV-protease inhibitors, antimycotics, antibiotics)