[Psychiatric homelessness research. From "psychopathology of the vagrant" to "homeless mentally ill"].

German psychiatrists around 1900 reported that dementia praecox and other mental disorders were common among homeless individuals. On the basis of the concept of psychopathy, homelessness in the 1920s was viewed as an "inferiority of character". The combination of psychiatric diagnosis and social prejudice was used as a justification for the "elimination of abnormal personalities" during the Third Reich. Growing numbers of homeless individuals in the last two decades stimulated a new interest in psychiatric research on the homeless. Larger epidemiological studies show high prevalence rates for severe mental disorders (schizophrenia, affective disorders, substance abuse). This points to the urgent need to develop sophisticated and sensible concepts to deal effectively with the complex problems associated with homelessness.