Relative State

1991 study turns up natural multiples?

December 11th, 2005

During recent internet wanderings, I found an interesting reference:

Ross, C. (1991). Epidemiology of Multiple Personality Disorder and Dissociation. Psychiatric Clinics of North America, 14 (3), 503-­517.

In summary: Colin Ross, founder of the Colin A. Ross Institute for Psychological Trauma, did a study where he interviewed 454 residents of Winnipeg with the DDIS (Dissociative Disorders Interview Schedule), to find out about the prevalence of dissociative disorders in the general population. 14 of the 454 (3.1%) met the DSM-III-R* criteria for MPD. However, eight out of the fourteen (1.8% of the population) didn’t report childhood trauma or extensive symptomatology…

It was apparent from visual inspection of the data that most of the MPD cases in the general population were radically different from clinical MPD patients. These people often did not report abuse histories and often reported experiencing little psychopathology. They had low DES scores (only one scored above 20). By reviewing the DDIS profile of each person positive for MPD I identified six individuals who appeared to have pathologic posttraumatic MPD, which was 1.3% of the entire sample.

These six individuals had abuse histories and substantial amounts of symptomatology. For instance, two met criteria for BPD and four had had a major depressive episode. Although they were clearly more symptomatic than the eight individuals positive for MPD who did not report childhood abuse, they were not as disturbed as clinically diagnosed MPD patients. Eight cases (1.8% of the entire sample) were possible false-positive diagnoses of MPD in individuals who did not report childhood trauma or extensive symptomatology.

IMPLICATIONS OF THE PREVALENCE STUDY

Heterogeneity of Individuals Meeting DSM-III-R Criteria for MPD

Although the study yielded only a small sample of 14 individuals positive for MPD, the findings raise a number of issues.

How should we think about the eight individuals who felt they had distinct personality states, but who did not appear to have clinical MPD? The first possibility is that the DDIS is not valid in nonclinical populations: These eight individuals may have DDNOS or no DD. In the absence of blind validation studies, all conclusions must be tentative.

The second possibility is that there is no problem with the DDIS, but instead with the DSM-III-R criteria. Perhaps the DDIS reflects the true prevalence of DSM-III-R MPD in the general population, but the DSM-III-R criteria yield false positives. Third, several of the eight apparently atraumatic individuals may be amnesic for abuse they experienced and unaware of their amnesia. Some of these individuals may be in a period of quiescence or remission, may have had more florid MPD in the past, or may develop overt MPD in the future if subjected to enough stress.

Another possibility is that multiplicity exists in a nonpathologic endogenous form in the general population. About 2% of people may be natural multiples who do not have dysfunctional posttraumatic MPD. They may simply have a highly dissociative psychic organization. If subjected to child abuse, these individuals would have developed clinical MPD with all its symptoms, self-destructiveness, and dysfunctional amnesia. The threshold for development of pathologic MPD in response to trauma is presumably low in such individuals, if they exist.

DSM-III-R criteria function well in clinical populations to differentiate MPD from other diagnostic groups; however it appears that more complex criteria are required to differentiate pathologic MPD with numerous personality states, complicated amnesia barriers, and severe trauma histories from individuals with nonpathologic atraumatic multiplicity.

The existence of mild, nonpathologic variants of MPD in the general population is consistent with the findings for all other forms of mental disorder. Simply having distinct personality states that feel subjectively like separate people may not in itself be a mental illness. This may be true even if the personality states have separate names and converse out loud with each other inside the person’s head. The DSM-III-R criteria for MPD do not make this distinction between psychiatric disorder and normal psychic organization. It is likely that the 14 individuals positive for MPD in the study have provided preliminary information about a heterogeneous group of people, some with disorders of varying etiology, and some with no psychiatric disorder.

A final consideration is that there may be something to the iatrogenesis model of MPD. Because the 14 MPD cases detected in the general population are all less symptomatic than the average clinically diagnosed MPD patient, it is possible that the process of entry into the mental health system and eventual diagnosis of MPD results in amplification of symptoms. If this occurs, it is very different from the de novo creation of MPD through iatrogenic influence. Countertherapeutic amplification of symptoms may result from too vigorous a pursuit of abuse memories or too much direct encouragement of separateness of personalities. Alternatively, the most complex and therapeutically difficult forms of MPD, with which specialists are familiar clinically, may have a prevalence no greater than 1 in 500 in the general population. A sample size of thousands of respondents might be required to resolve these issues. (See also Kluft’s presentations on MPDs in this issue.)

I’m not aware of any follow-up research on this subpopulation, and a quick search didn’t turn up any.

* A. The existence within the person of two or more distinct personalities or personality states (each with its own relatively enduring pattern of perceiving, relating to, and thinking about the environment and self).

B. At least two of these personalities or personality states recurrently take full control of the person’s behavior.

Note that these do not include amnesia; that criterion was added in the DSM-IV along with the name change to DID.

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