background  The clinical picture of cycloid psychosis was introduced in 1928 by the German Kleist and further developed by his pupil Leonard. Together with Wernicke they did not agree with Kraepelin's classification of psychoses into two types: manic-depressive psychosis and schizophrenia. According to some authors cycloid psychosis is a validated diagnosis which can also now be clearly distinguished from bipolar disorder and schizophrenia.
aim  To search the literature for articles that describe the historical development and the modern clinical relevance of the concept of cycloid psychosis.
method  Literature was obtained by using Medline search, using as key words psychosis, cycloid, postpartum and history. The acquired articles were used to gain related articles.
results and conclusions  Cycloid psychosis, which is mainly luxated following childbirth, has symptoms of both a (schizo-)affective disorder and a psychotic disorder (Not Otherwise Specified). This illness is not classified in the DSM-IV, but it is in the ICD-10. Of the psychiatric illnesses that develop after childbirth 47-54% is a cycloid psychosis. According to different authors cycloid psychosis is a validated diagnosis of a nosologic entity. However the (long-term) medical treatment and the possible genetic inheritance have not been studied systematically and so far investigations have not met the standards of modern research. Consequently it is difficult to assess the clinical relevance of cycloid psychosis.