http://en.wikipedia.org/wiki/Dissociative_identity_disorder
Multiple personality disorder began to emerge as a separate disorder in the 1970's when an initially small number of clinicians worked to re-established MPD as a legitimate diagnosis.[57] In 1974, the highly influential book Sybil was published and six years later the diagnosis of multiple personality disorder was included in the DSM.(1980) As media coverage spiked, diagnoses climbed. There were 200 reported cases of MPD from 1880 to 1979, and 20,000 from 1980 to 1990 Joan Acocella reports that 40,000 cases were diagnosed from 1985 to 1995.
The majority of diagnoses are made in North America, particularly the United States, and in English-speaking countries more generally with reports recently emerging from other countries (!!!)
The DSM does not provide an estimate, and suggests different explanations for the sharp rise in incidence of DID. Possible reasons suggested for the increase in incidence and prevalence of DID over time [/i]include the condition being misdiagnosed
The causes of dissociative identity disorder have not been identified,
From 1880 to 1979 : 200 reported cases of MPD (2 per year )
From 1980 to 1990 : 20,000 cases (2000 per year)
From1985 to 1995 : 40,000 cases (doubled in 5 years )
http://environment.newscientist.com/article/mg15120384.800-review--the-splintered-self.html
Strictly speaking, recovered memory and multiple personality disorder (MPD) are independent issues, as Schacter makes clear, but they have been entwined for three reasons. The first is that, according to some data, MPD is frequently caused by severe sexual abuse before the age of five. The second reason has to do with the actions of therapists, who are accused of creating both false memories of sexual abuse and MPD.The third reason is a little more complicated, as both involve loss of memory. People who wish to claim in a court that all recovered memories are false would have a strong and universal defence if they could say there were no mechanisms of memory available that could account for the phenomenon of amnesia that lifts after a twenty-year gap. If this amnesia is genuine, then there has to be a mechanism to explain it, which would account for the amnesia in recovered memory. Members of the British False Memories Society are disbelievers in recovered memory, for example, and they are mostly disbelievers in multiple personalities.
One interesting remark on hearing voices or telepatical messages: it is associated in the first place with DID another pretty new with a sudden and big increaese in numbers in the 80ties that overlaps a lot with all kind of recovered memories experience and is typical for remotely targeted individuals but also for the alien anductees who very often discribe telepatically to communicate with the aliens who abducted them There is also worldwide mayny groups of voichearers comming up and that phenomenon is also pretty recent)
psychiatric categories of patients that hear voices; schizophrenia > (around 50 percent); affective psychosis (around 25 percent) and > dissociative disorders (AROUND 80 PROCENT ) (Honig et al., 1998).