Abstract
The diagnostic distinction of bipolar affective disorder and schizophrenia in current classification systems ICD-10 and DSM IV is based on Kraepelin's definition of "dementia praecox" and "maniodepressive psychosis". The authors review the similarities and distinctions between both disorders in a wide range from psychopathology to neuroimaging methods with an emphasis on genetic findings as a major source of evidence of an overlap between bipolar disorder and schizophrenia.