Multiple identity disorder frequently co-occurs with other psychiatric diagnoses, such as anxiety disorders (especially post-traumatic stress disorder-PTSD), mood disorders, somatoform disorders, eating disorders, as well as sleep problems and sexual dysfunction. The symptoms of the disorder have a considerable overlap with borderline personality disorder.
One of ten photogravure portraits of Louis Vivé published in Variations de la personnalité by Bourru and Burot.
In Greek mythology, the god Janus who was also a King of Latium was described as having "two-faces", but primarily, before the 19th century, people exhibiting symptoms similar to those were believed to be possessed.
An intense interest in spiritualism, parapsychology, and hypnosis continued throughout the 19th and early 20th centuries, running in parallel with John Locke's views that there was an association of ideas requiring the coexistence of feelings with awareness of the feelings. Hypnosis, which was pioneered in the late 18th century by Franz Mesmer and Armand-Marie Jacques de Chastenet, Marques de Puységur, challenged Locke's association of ideas. Hypnotists reported what they thought were second personalities emerging during hypnosis and wondered how two minds could coexist.
The 19th century saw a number of reported cases of multiple personalities which Rieber estimated would be close to 100. Epilepsy was seen as a factor in some cases, and discussion of this connection continues into the present era.
By the late 19th century there was a general acceptance that emotionally traumatic experiences could cause long-term disorders which may manifest with a variety of symptoms. These conversion disorders were found to occur in even the most resilient individuals, but with profound effect in someone with emotional instability like Louis Vivé (1863-?) who suffered a traumatic experience as a 13 year-old when he...