Dissociative disorders are not among the more common psychi-atric illnesses but are not rare. Few good epidemiological studies have been performed. Some estimate the prevalence at only 1 per 10 000 in the population, but far higher proportions are re-ported among psychiatric populations. In fact, the prevalence of the disorder seems to be associated to the specific population un-der study. For example, data from the general population suggest that the numbers are as high as 1%. On the other hand, the data seem to indicate that the numbers are even higher in specialized inpatient populations, as high as 3%.
There has been a rise in reported cases, which may be attributed to greater awareness of the diagnosis among mental health professionals, to the availability of specific criteria, and to previous misdiagnosis of DID as schizophrenia or borderline per-sonality disorder. Some experts attribute possible underdiagnosis to family disavowal of sexual and physical abuse. However, there is also controversy about possible overdiagnosis of the syndrome, while others propose that the increase is the result of hypnotic suggestion and inadequate handling by therapists. Individuals who most commonly have the disorder are highly hypnotizable and therefore especially sensitive to suggestion or cultural influ-ences. Although psychiatrists’ expectations amplified with hyp-nosis may account for some cases, they cannot account for many patients diagnosed without benefit of hypnosis or by “skeptical” psychiatrists.
Women make-up the majority of cases, accounting for 90% of the cases or more, in some studies. Strangely, the most common dissociative disorder diagnosis falls into the “not oth-erwise specified” category, both in the USA and in nonWestern countries, where dissociative trance and possession trance are the most common dissociative disorder diagnoses. Dissociative disorders are ubiquitous around the world, although the struc-ture of the symptoms varies across cultures. Indeed, the symp-tomatology reflects cultural biases. In Western cultures, which emphasize the importance of the individual, dissociation often takes the form of dissociated elements of individual personality, while in Eastern cultures, which are more sociocentric, posses-sion trance, in which patients feel themselves to be taken over by an outside entity or entities, is more common.