Dissociative identity disorder
Before 1900 it was thought DID was caused by spirits or ghosts who controlled people's behavior.  The first case of DID described in medicine was in 1646 by the Swiss doctor Paracelsus.  DID was very uncommon until the 1970s.  Between 1980 and 1990 the number of cases reported in medicine went from about 200 to more than 20,000.  In 1994, the 4th edition of the DSM was published, which changed the name from "multiple personality disorder" to "dissociative identity disorder".  The DSM also changed how DID was diagnosed.  Many scientific articles were written about DID during the same period, though after 1995 the number of articles published every year decreased. Today there is little research on DID.