Dissociative Experiences Among Psychiatric Inpatients Colin A. Ross, M.D., Geri Anderson, and G. Ron Norton, Ph.D.
Abstract: The Dissociative
Experiences Scale was administered to 299 inpatients on an acute care general adult psychiatric ward over a 2-year period. The average score was 14.6, which is significantly higher than the mean for the general population. About one in six inpatients reported very high scores above 50 on the seven most common items in the scale, indicating a high level of dissociative psychopathology. Based on the responses to four items which form a scale factor called Activities of Dissociated States, an estimate is made that 6%8% of general adult inpatients may have multiple personality disorder. Dissociative psychopathology is common on inpatient units.
Introduction Dissociative experiences have been studied in a variety of clinical and nonclinical populations [l-9]. Chu and Dill [7] studied the dissociative experiences of 98 female psychiatric inpatients using the Dissociative Experiences Scale (DES) [l], and found that 25% scored above the median for posttraumatic stress disorder. They found significant correlations between scores on this scale and histories of childhood physical and sexual abuse. A study of a large sample of the general population using the Dissociative Experiences Scale led
From the Charter Hospital of Dallas, Piano, Texas; the Department of Psychiatry, St. Boniface Hospital, Winnipeg, Manitoba, Canada; the Department of Psychiatry, University of Manitoba, Manitoba, Canada; and the Department of Psychology, University of Winnipeg, Winnipeg, Manitoba, Canada. Address reprint requests to: Colin A. Ross, M.D., 1701 Gateway Blvd., Ste. 349, Richardson, TX 75080. This paper was presented at the Seventh Annual International Conference on Multiple Personality/Dissociative States, Chicago, November 9, 1990.
350 ISSN 0163~8343/92/$5.00
R.P.N.,
William P. Fleisher, M.D.,
the authors to predict that the prevalence of dissociative disorders could be in the range of 5%10%, making them about as common as anxiety and affective disorders [9]. Follow-up study of the sample with structured diagnostic interviews confirmed that 11.2% of individuals in the general population have or have had a DSM-III-R dissociative disorder [lo]. Dissociative disorders should be relatively common among psychiatric inpatients, and dissociative symptoms should occur quite frequently among inpatients as a group, irrespective of diagnosis. To determine the prevalence of dissociative experiences among psychiatric inpatients, and to derive a prediction of the frequency of the most chronic and complex dissociative disorder, multiple personality disorder (MPD), among general adult acute-care, psychiatric inpatients, we administered the DES to inpatients at our hospital over a 2-year period.
Methods The Dissociative Experiences Scale The DES is a 28-item self-report instrument with a test-retest reliability of 0.84 and good split-half reliability [l]. The ability of group median scores on the scale to differentiate MPD from other diagnostic groups has been replicated [3], and norms for the general population are available [9]. In a large multicenter study, the DES performed well as a predictor of MPD in a diagnostically heterogeneous sample of 1340 patients: the DES was able to corGcr~alHosptd Psychiatry 14, 350-354, 1992 0 1992 Elsevier Science Publishing Co., Inc. 655 Avenue of the Americas, New York, NY 10010
Dissociation
rectly identify 85.5% of the MPD subjects with a specificity of 88.8% [ll]. The scale yields 28-item scores ranging from 0 to 100; these are summed and divided by 28 to give an overall score. Further information on the validity and reliability of the DES is contained in recent correspondence in the Americnll ~owzal of Psychiatry [12-141. A principal components analysis of 1055 DES questionnaires completed by a random sample of the general population yielded three factors which accounted for 47.1% of the combined variance of the scores [5]. The first factor, absorption/imaginative involvement, consists of relatively common benign experiences. The second factor, activities of dissociated states, may be a powerful predictor of MPD. The third factor, depersonalization/derealization, may be a predictor of dissociative disorders, but not specifically of MPD.
Subjects All individuals admitted to two 23-bed, acute-care, general adult inpatient units at our hospital between July 18, 1988 and July 17, 1990 were subjects for the study. Those with a diagnosis of MPD made prior to admission were excluded. Subjects were approached by the research nurse, the study was explained to them, and those agreeing to participate gave written consent. No subjects in the study had been referred to the hospital for treatment of dissociative disorders. Ethical approval had been received from the Faculty Committee on the Use of Human Subjects in Research at our university.
Data Analysis DES data were analyzed descriptively. Mean scores for each of the 28 items of the DES were calculated, as was the percentage of subjects positive for each item. Subjects completing the DES were compared with those not completing the DES on age and gender using t tests and on the frequency of various clinical diagnoses using Chi square tests. Scores of the subjects in this study were compared with those in the general population using a goodness of fit test: f or this purpose, scores were divided into ranges of O-10, 11-20, 21-30, and greater than 30. Finally, the percentage of inpatient subjects scoring above 30 on each of the four items of the Activities of Dissociated States factor was determined. Thirty was chosen as a cutoff score because overall DES scores in this range are sugges-
Among
Inpatients
tive of MPD in clinical populations [l-3,16]. From these findings a prediction was made as to what percentage of the subjects have MPD. Our purpose was to make a prediction of the frequency of MPD based on a conservative cutoff score derived from previous literature [17]. Steinberg et al. [17] recommend a DES cutoff score of 15-20 for detecting dissociative disorders, but patients with MPD have higher scores than those with other dissociative disorders (161; therefore, we used a higher cutoff score in predicting the frequency of MPD.
Demographic
Characteristics
of Subjects
Four hundred and eighty-four individuals were admitted during the 2 years of the study. Of these, 299 (61.8%) completed the DES. Reasons for not completing the DES included the following: refused (N = 80), poor comprehension (N = 48), organic disorder (N = 5), missed (N = 41), and other (N = 11). The percentage of subjects completing the scale who were female (62.1%) did not differ from the percentage of those not completing the scale who were female (61.6%) (t = O.l.df = 481, n.s.). The average age of the subjects completing the DES was 40.1 (SD 15.9) years compared with 44.6 (SD 17.8) years for those not completing the DES (t = 2.9, df = 476, ,U < 0.004). Variation in the degrees of freedom for these analyses are due to missing data. Subjects who completed the DES did not differ from those who did not on the frequency of bipolar mood disorder (N = 125), schizophrenia (N = 69), personality disorder (N = 150), or miscellaneous other diagnoses (N = 89). However, 87 (29.1%) completers received a clinical diagnosis of major depressive episode compared with 36 (19.5%) noncompleters (x’ = 5.1, df = 1, ,U< 0.03); 33 (11.0%) DES completers received a diagnosis of psychotic disorder not classified elsewhere compared with 37 (20.0%) DES noncompleters (x’ = 6.7, df = 1, p < 0.01); and 32 (10.2%) DES completers received a diagnosis of substance abuse compared with 40 (21.6%) DES noncompleters (x’ = 9.9, df = 1, p < 0.002).
Dissociative
Experiences
of Subjects
The average DES score among the inpatients was 14.6 (SD 14.2), the median score was 9.1, and the range was O-79.2. This was significantly higher than the average score in the general population, which was 10.8 (SD 10.2) (t = 5.19, df = 1352, 351
C. A. Ross et al.
Table 1. Distribution of DES scores among psychiatric inpatients and in the general population General population (IV = 1055)
Psychiatric inpatients (N = 299)
Dissociative experiences scale score
No. subjects
% of Total
No. subjects
% of Total
l-10 11-20 21-30 Greater than 30
676 244 82 53
64.1 23.1 7.8 5.1
162 47 43 46
54.2 15.7 14.4 15.4
p < 0.001). A goodness of fit test showed that a higher proportion of inpatients had scores in the higher ranges compared with the general population (x2 = 90.253, df = 2, p < 0.00001). These findings are shown in Table 1. Average item scores, prevalence of each item in the sample, and the DES factor to which each item belongs are shown in Table 2. The four rarest items all belonged to factor 2, activities of dissociated states. The 10 most common items all belonged to factor 1, absorption/imaginative involvement. The intermediate items were from factor 3 or were items that did not load onto any factor at p < 0.05, plus two items from factor 1. In Table 3 the percentage of subjects scoring above 30 on each of the four items of the Activities of Dissociated States factor are shown.
Discussion Dissociative experiences are common among psychiatric inpatients, and more common in this group than in the general population. The finding that 15.4% of psychiatric inpatients score above 30 on the DES suggests that DSM-III-R dissociative disorders are common in this clinical group. Based on the DES factor Activities of Dissociated States, we would predict that at least 6% of general adult psyif screened carefully, would chiatric inpatients, meet DSM-III-R criteria for MPD. This is close to the actual frequency of MPD in this population, which is 5.4% [18] as determined by follow-up assessment for dissociative disorders of all subjects scoring above 20 on the DES. In the follow-up study reported elsewhere [15], all subjects scoring above 20 on the DES were interviewed with the Dissociative Disorders Interview Schedule [16]. All subjects positive for MPD and matched comparison 352
subjects were then interviewed by a clinician blind to structured interview findings for validation of the clinical diagnoses. In this follow-up phase of the study, 16 inpatients, or 5.4% of the 484 individuals admitted received both a structured interview and a clinical diagnosis of MPD. One can therefore conclude that a cutoff score of 30 for items in factor 2 of the DES will yield a good estimate of the frequency of MPD in a clinical population. The factor 2 item with the lowest percentage of subjects scoring above 30 gives the estimated percentage of subjects in the sample with MPD. For an individual patient, a DES score above 30 indicates an increased likelihood of MPD but is not in itself diagnostic of the disorder [ll]. There is symmetry in the data, as shown in Table 1. A principal components analysis from a random sample of the general population [15] can predict almost perfectly which DES items are rarest among inpatients, which most common, and which intermediate in frequency. As dissociative experiences are common in the sample, they must be prominent in a variety of psychiatric disorders, not just among those individuals with DSM-III-R dissociative disorders. Careful tabulation of dissociative symptoms, and of the childhood trauma histories that often go along with high DES scores, might identify phenomenological subtypes of affective disorder or psychosis. Such subtypes might respond differently to treatment interventions, or have other distinct correlates of clinical significance. Examination of Table 1, given the standard deviations of the DES subitem scores, reveals that at least 15% of psychiatric inpatients have scores above 50 on the seven most common forms of absorption/imaginative involvement. This dimension of psychopathology is present to an extreme degree in about one of six psychiatric inpatients. Because dissociative symptomatology is often mistaken for psychosis [19,20], careful assessment of such symptoms among psychiatric inpatients should be part of routine assessments. One cannot generalize from this sample to all psychiatric inpatients in North America. However, our sample of 299 appears to be representative of the overall 484 inpatients who were admitted over the 2 years of our study. We do not think that the statistically significant difference in age of 4 years between those who did complete the DES and those who did not is clinically significant. There is no specific reason to think that our inpatients differ dramatically from other acute-care, teaching hos-
Dissociation
Table
2. Frequency
of dissociative
Dissociative
experiences
experiences
among 299 psychiatric
Mean score
Missing part of a conversation Remembering past so vividly one seems to be reliving it Able to ignore pain Usually difficult things can be done with ease & spontaneity Staring into space Absorption in television program or movie Not sure whether one has done something or only thought about it Feeling as though one were two different people Talking outloud to oneself when alone So involved in fantasy that it seems real Hearing voices inside one’s head Not sure if remembered an event happened or was a dream Being accused of lying when one is telling the truth Looking at the world through a fog Finding evidence of having done things one can’t remember Being approached by people one doesn’t know who call one by a different name Other people and objects do not seem real Being in a familiar place but finding it unfamiliar Not remembering important events in one’s life
remember doing happened during the trip
Driving a car and realizing one doesn’t remember what Not recognizing one’s reflection in a mirror Not recognizing friends or family members Finding oneself in a place but unaware how one got there Finding unfamiliar things among one’s belongings Finding oneself dressed in clothes one can’t remember putting on
Inpatients
inpatients
scale item
Seeing oneself as if one were looking at another person Feeling as though one’s body is not one’s own Finding notes or drawings that one must have done but doesn’t
Among
29.5 24.5 24.3 22.7 22.6 21.2 20.8 19.0 18.7 18.3 17.0 16.0 15.8 13.8 13.6 12.1 11.9 11.9 11.4 9.5 9.2 9.1 8.5 66 6.0 5.8 5.7 2.8
(25.3) (29.1) (28.9) (27.0) (27.4) (28.1) (25.8) (25.5) (26.1) (28.3) (29.3) (23.7) (25.3) (24.7) (22.1) (20.1) (22.9) (20.2) (21.0) (19.4) (19.9) (18.9) (17.3) (17.5) (15.1) (13.7) (15.1) (10.5)
Prevalence ‘% 82.6 67.9 64.5 66.2 64.5 56.9 62.2 51.5 55.9 47.8 31.1 52.2 45.6 39.5 19.8 43.5 26.8 31.8 36.1 21.8 28.8 31.4 26.1 23.1 26.8 38.4 21.7 13.7
Factor
1 1
1 1 1
1 1 1 1 1 3 1 3
1 3 --3 3 2 2 2 2
Factor 1 = Absorption/Imaginative Involvement; factor 2 = Activities of Dissociated States; factor 3 = DepersonalizationiDereali zation; -indicates items that did not lead onto anvi factor at ZJc.05. Factors from principal components analysis of general population sample N = 1055.
pita1 populations. Because patients were not admitted to the hospital specifically for treatment of dissociative disorders, the sample was probably not skewed towards an unusually high frequency Table
3. Percentage of 299 psychiatric inpatients with high scores on the Activities of Dissociated States factor of the DES
Item Not recognizing friends or family Finding oneself in a place but unaware how one got there Finding unfamiliar things among one‘s belongings Finding oneself dressed in clothes one can’t remember putting on
% of Subjects scoring 30 or greater 6.3 7.9 17.2
6.5
of MPD. The fact that the patients completing the DES differed on the frequency of three clinical diagnoses compared with the noncompleters did not introduce an obvious major bias, because the groups did not differ on four other diagnoses. Additionally, the DES completers had a higher frequency of depression but lower frequencies of substance abuse and psychotic disorder not elsewhere classified, so there was no consistent pattern of difference between the two groups. Bearing in mind the need for replication, our findings suggest that both dissociative symptomatology and DSM-III-R dissociative disorders are common among psychiatric inpatients. It appears that a cutoff score of 30 for factor 2 items on the DES can predict the frequency of MPD in a clinical population. Further research is required to determine whether patients with high DES scores within nondissociative disorder diagnostic groups such as
353
C. A. Ross et al.
mood disorders ment compared
have a different response to treatwith those with low DES scores. 10.
Supported by grants from the Manitoba Mental Health Research Foundation and the Manitoba Health Research Council
References 1. Bernstein EM, Putnam FW: Development, reliability and validity of a dissociation scale. J Nerv Ment Dis 1741727-735, 1986 2. Ross CA, Norton GR, Anderson G: The dissociative experiences scale: a replication study. Dissociation 1:21-22, 1988 3. Putnam FW: Diagnosis and Treatment of Multiple Personality Disorder. New York, Guilford Press, 1989 4. Loewenstein RJ, Putnam FW: A comparison study of dissociative symptoms in patients with complex partial seizures, multiple personality disorder, and posttraumatic stress disorder. Dissociation 1:17-23, 1988 5. Sanders B, McRoberts G, Tollefson C: Childhood stress and dissociation in a college population. Dissocia tion 2: 17-23, 1989 6. Sanders 8, Giolas MH: Dissociation and childhood trauma in psychologically disturbed adolescents. Am J Psychiatry 148:50-54, 1991 7. Chu JA, Dill DL: Dissociative symptoms in relation to childhood physical and sexual abuse. Am J Psychiatry 147:887-892, 1990 8. Ross CA, Ryan L, Anderson G, Ross D, Hardy L: Dissociative experiences in adolescents and college students. Dissociation 2:239-242, 1989 9. Ross CA, Joshi S, Currie R: Dissociative experiences
354
11.
12. 13.
14. 15.
16.
17.
18.
19.
20.
in the general population. Am J Psychiatry 147:15471552, 1990 Ross CA: Epidemiology of multiple personality disorder and dissociation. Psych Clin N Am 14:503-517, 1990 Carlson EB, Putnam FW, Ross C, et al: A discriminant validity analysis of the dissociative experiences scale: a multicenter study. In Braun BG, Carlson EB (eds), Proc 7th Int Conf on Multiple PersonalityDissociative States, Chicago, Rush-Presbyterian-St. Luke’s Medical Center, 1990, p 141 Weiner A: The dissociative experiences scale. Am J Psychiatry 149:143, 1992 Putnam FW, Chu JA, Dill DL: The dissociative experiences scale (reply to Weiner). Am J Psychiatry 149:143-144, 1992 Sanders B: The dissociative experiences scale (reply to Weiner). Am J Psychiatry 149:144, 1992 Ross CA, Miller SD, Reagor I’, Bjornson L, Fraser GA, Anderson G: Structured interview data on 102 cases of multiple personality disorder from four centers. Am J Psychiatry 147:596-601, 1990 Ross CA, Joshi S, Currie R: Dissociation in the general population: identification of three factors. Hosp Comm Psychiatry 42:297-301, 1991 Steinberg M, Rounsaville B, Cicchetti D: Detection of dissociative disorders in psychiatric patients by a screening instrument and a structured diagnostic interview. Am J Psychiatry 148:1050-1054, 1991 Ross CA, Anderson G, Fleisher WI’, Norton GR: The frequency of multiple personality disorder among psychiatric inpatients. Am J Psychiatry 148:17171720, 1991 Bliss EL: Multiple personalities. A report of 14 cases with implications for schizophrenia. Arch Gen Psychiatry 37:1388-1397, 1980 Kluft RI’: First-rank symptoms as a diagnostic clue to multiple personality disorder. Am J Psychiatry 144:293-298, 1987
Abstract: The Dissociative
Experiences Scale was administered to 299 inpatients on an acute care general adult psychiatric ward over a 2-year period. The average score was 14.6, which is significantly higher than the mean for the general population. About one in six inpatients reported very high scores above 50 on the seven most common items in the scale, indicating a high level of dissociative psychopathology. Based on the responses to four items which form a scale factor called Activities of Dissociated States, an estimate is made that 6%8% of general adult inpatients may have multiple personality disorder. Dissociative psychopathology is common on inpatient units.
Introduction Dissociative experiences have been studied in a variety of clinical and nonclinical populations [l-9]. Chu and Dill [7] studied the dissociative experiences of 98 female psychiatric inpatients using the Dissociative Experiences Scale (DES) [l], and found that 25% scored above the median for posttraumatic stress disorder. They found significant correlations between scores on this scale and histories of childhood physical and sexual abuse. A study of a large sample of the general population using the Dissociative Experiences Scale led
From the Charter Hospital of Dallas, Piano, Texas; the Department of Psychiatry, St. Boniface Hospital, Winnipeg, Manitoba, Canada; the Department of Psychiatry, University of Manitoba, Manitoba, Canada; and the Department of Psychology, University of Winnipeg, Winnipeg, Manitoba, Canada. Address reprint requests to: Colin A. Ross, M.D., 1701 Gateway Blvd., Ste. 349, Richardson, TX 75080. This paper was presented at the Seventh Annual International Conference on Multiple Personality/Dissociative States, Chicago, November 9, 1990.
350 ISSN 0163~8343/92/$5.00
R.P.N.,
William P. Fleisher, M.D.,
the authors to predict that the prevalence of dissociative disorders could be in the range of 5%10%, making them about as common as anxiety and affective disorders [9]. Follow-up study of the sample with structured diagnostic interviews confirmed that 11.2% of individuals in the general population have or have had a DSM-III-R dissociative disorder [lo]. Dissociative disorders should be relatively common among psychiatric inpatients, and dissociative symptoms should occur quite frequently among inpatients as a group, irrespective of diagnosis. To determine the prevalence of dissociative experiences among psychiatric inpatients, and to derive a prediction of the frequency of the most chronic and complex dissociative disorder, multiple personality disorder (MPD), among general adult acute-care, psychiatric inpatients, we administered the DES to inpatients at our hospital over a 2-year period.
Methods The Dissociative Experiences Scale The DES is a 28-item self-report instrument with a test-retest reliability of 0.84 and good split-half reliability [l]. The ability of group median scores on the scale to differentiate MPD from other diagnostic groups has been replicated [3], and norms for the general population are available [9]. In a large multicenter study, the DES performed well as a predictor of MPD in a diagnostically heterogeneous sample of 1340 patients: the DES was able to corGcr~alHosptd Psychiatry 14, 350-354, 1992 0 1992 Elsevier Science Publishing Co., Inc. 655 Avenue of the Americas, New York, NY 10010
Dissociation
rectly identify 85.5% of the MPD subjects with a specificity of 88.8% [ll]. The scale yields 28-item scores ranging from 0 to 100; these are summed and divided by 28 to give an overall score. Further information on the validity and reliability of the DES is contained in recent correspondence in the Americnll ~owzal of Psychiatry [12-141. A principal components analysis of 1055 DES questionnaires completed by a random sample of the general population yielded three factors which accounted for 47.1% of the combined variance of the scores [5]. The first factor, absorption/imaginative involvement, consists of relatively common benign experiences. The second factor, activities of dissociated states, may be a powerful predictor of MPD. The third factor, depersonalization/derealization, may be a predictor of dissociative disorders, but not specifically of MPD.
Subjects All individuals admitted to two 23-bed, acute-care, general adult inpatient units at our hospital between July 18, 1988 and July 17, 1990 were subjects for the study. Those with a diagnosis of MPD made prior to admission were excluded. Subjects were approached by the research nurse, the study was explained to them, and those agreeing to participate gave written consent. No subjects in the study had been referred to the hospital for treatment of dissociative disorders. Ethical approval had been received from the Faculty Committee on the Use of Human Subjects in Research at our university.
Data Analysis DES data were analyzed descriptively. Mean scores for each of the 28 items of the DES were calculated, as was the percentage of subjects positive for each item. Subjects completing the DES were compared with those not completing the DES on age and gender using t tests and on the frequency of various clinical diagnoses using Chi square tests. Scores of the subjects in this study were compared with those in the general population using a goodness of fit test: f or this purpose, scores were divided into ranges of O-10, 11-20, 21-30, and greater than 30. Finally, the percentage of inpatient subjects scoring above 30 on each of the four items of the Activities of Dissociated States factor was determined. Thirty was chosen as a cutoff score because overall DES scores in this range are sugges-
Among
Inpatients
tive of MPD in clinical populations [l-3,16]. From these findings a prediction was made as to what percentage of the subjects have MPD. Our purpose was to make a prediction of the frequency of MPD based on a conservative cutoff score derived from previous literature [17]. Steinberg et al. [17] recommend a DES cutoff score of 15-20 for detecting dissociative disorders, but patients with MPD have higher scores than those with other dissociative disorders (161; therefore, we used a higher cutoff score in predicting the frequency of MPD.
Demographic
Characteristics
of Subjects
Four hundred and eighty-four individuals were admitted during the 2 years of the study. Of these, 299 (61.8%) completed the DES. Reasons for not completing the DES included the following: refused (N = 80), poor comprehension (N = 48), organic disorder (N = 5), missed (N = 41), and other (N = 11). The percentage of subjects completing the scale who were female (62.1%) did not differ from the percentage of those not completing the scale who were female (61.6%) (t = O.l.df = 481, n.s.). The average age of the subjects completing the DES was 40.1 (SD 15.9) years compared with 44.6 (SD 17.8) years for those not completing the DES (t = 2.9, df = 476, ,U < 0.004). Variation in the degrees of freedom for these analyses are due to missing data. Subjects who completed the DES did not differ from those who did not on the frequency of bipolar mood disorder (N = 125), schizophrenia (N = 69), personality disorder (N = 150), or miscellaneous other diagnoses (N = 89). However, 87 (29.1%) completers received a clinical diagnosis of major depressive episode compared with 36 (19.5%) noncompleters (x’ = 5.1, df = 1, ,U< 0.03); 33 (11.0%) DES completers received a diagnosis of psychotic disorder not classified elsewhere compared with 37 (20.0%) DES noncompleters (x’ = 6.7, df = 1, p < 0.01); and 32 (10.2%) DES completers received a diagnosis of substance abuse compared with 40 (21.6%) DES noncompleters (x’ = 9.9, df = 1, p < 0.002).
Dissociative
Experiences
of Subjects
The average DES score among the inpatients was 14.6 (SD 14.2), the median score was 9.1, and the range was O-79.2. This was significantly higher than the average score in the general population, which was 10.8 (SD 10.2) (t = 5.19, df = 1352, 351
C. A. Ross et al.
Table 1. Distribution of DES scores among psychiatric inpatients and in the general population General population (IV = 1055)
Psychiatric inpatients (N = 299)
Dissociative experiences scale score
No. subjects
% of Total
No. subjects
% of Total
l-10 11-20 21-30 Greater than 30
676 244 82 53
64.1 23.1 7.8 5.1
162 47 43 46
54.2 15.7 14.4 15.4
p < 0.001). A goodness of fit test showed that a higher proportion of inpatients had scores in the higher ranges compared with the general population (x2 = 90.253, df = 2, p < 0.00001). These findings are shown in Table 1. Average item scores, prevalence of each item in the sample, and the DES factor to which each item belongs are shown in Table 2. The four rarest items all belonged to factor 2, activities of dissociated states. The 10 most common items all belonged to factor 1, absorption/imaginative involvement. The intermediate items were from factor 3 or were items that did not load onto any factor at p < 0.05, plus two items from factor 1. In Table 3 the percentage of subjects scoring above 30 on each of the four items of the Activities of Dissociated States factor are shown.
Discussion Dissociative experiences are common among psychiatric inpatients, and more common in this group than in the general population. The finding that 15.4% of psychiatric inpatients score above 30 on the DES suggests that DSM-III-R dissociative disorders are common in this clinical group. Based on the DES factor Activities of Dissociated States, we would predict that at least 6% of general adult psyif screened carefully, would chiatric inpatients, meet DSM-III-R criteria for MPD. This is close to the actual frequency of MPD in this population, which is 5.4% [18] as determined by follow-up assessment for dissociative disorders of all subjects scoring above 20 on the DES. In the follow-up study reported elsewhere [15], all subjects scoring above 20 on the DES were interviewed with the Dissociative Disorders Interview Schedule [16]. All subjects positive for MPD and matched comparison 352
subjects were then interviewed by a clinician blind to structured interview findings for validation of the clinical diagnoses. In this follow-up phase of the study, 16 inpatients, or 5.4% of the 484 individuals admitted received both a structured interview and a clinical diagnosis of MPD. One can therefore conclude that a cutoff score of 30 for items in factor 2 of the DES will yield a good estimate of the frequency of MPD in a clinical population. The factor 2 item with the lowest percentage of subjects scoring above 30 gives the estimated percentage of subjects in the sample with MPD. For an individual patient, a DES score above 30 indicates an increased likelihood of MPD but is not in itself diagnostic of the disorder [ll]. There is symmetry in the data, as shown in Table 1. A principal components analysis from a random sample of the general population [15] can predict almost perfectly which DES items are rarest among inpatients, which most common, and which intermediate in frequency. As dissociative experiences are common in the sample, they must be prominent in a variety of psychiatric disorders, not just among those individuals with DSM-III-R dissociative disorders. Careful tabulation of dissociative symptoms, and of the childhood trauma histories that often go along with high DES scores, might identify phenomenological subtypes of affective disorder or psychosis. Such subtypes might respond differently to treatment interventions, or have other distinct correlates of clinical significance. Examination of Table 1, given the standard deviations of the DES subitem scores, reveals that at least 15% of psychiatric inpatients have scores above 50 on the seven most common forms of absorption/imaginative involvement. This dimension of psychopathology is present to an extreme degree in about one of six psychiatric inpatients. Because dissociative symptomatology is often mistaken for psychosis [19,20], careful assessment of such symptoms among psychiatric inpatients should be part of routine assessments. One cannot generalize from this sample to all psychiatric inpatients in North America. However, our sample of 299 appears to be representative of the overall 484 inpatients who were admitted over the 2 years of our study. We do not think that the statistically significant difference in age of 4 years between those who did complete the DES and those who did not is clinically significant. There is no specific reason to think that our inpatients differ dramatically from other acute-care, teaching hos-
Dissociation
Table
2. Frequency
of dissociative
Dissociative
experiences
experiences
among 299 psychiatric
Mean score
Missing part of a conversation Remembering past so vividly one seems to be reliving it Able to ignore pain Usually difficult things can be done with ease & spontaneity Staring into space Absorption in television program or movie Not sure whether one has done something or only thought about it Feeling as though one were two different people Talking outloud to oneself when alone So involved in fantasy that it seems real Hearing voices inside one’s head Not sure if remembered an event happened or was a dream Being accused of lying when one is telling the truth Looking at the world through a fog Finding evidence of having done things one can’t remember Being approached by people one doesn’t know who call one by a different name Other people and objects do not seem real Being in a familiar place but finding it unfamiliar Not remembering important events in one’s life
remember doing happened during the trip
Driving a car and realizing one doesn’t remember what Not recognizing one’s reflection in a mirror Not recognizing friends or family members Finding oneself in a place but unaware how one got there Finding unfamiliar things among one’s belongings Finding oneself dressed in clothes one can’t remember putting on
Inpatients
inpatients
scale item
Seeing oneself as if one were looking at another person Feeling as though one’s body is not one’s own Finding notes or drawings that one must have done but doesn’t
Among
29.5 24.5 24.3 22.7 22.6 21.2 20.8 19.0 18.7 18.3 17.0 16.0 15.8 13.8 13.6 12.1 11.9 11.9 11.4 9.5 9.2 9.1 8.5 66 6.0 5.8 5.7 2.8
(25.3) (29.1) (28.9) (27.0) (27.4) (28.1) (25.8) (25.5) (26.1) (28.3) (29.3) (23.7) (25.3) (24.7) (22.1) (20.1) (22.9) (20.2) (21.0) (19.4) (19.9) (18.9) (17.3) (17.5) (15.1) (13.7) (15.1) (10.5)
Prevalence ‘% 82.6 67.9 64.5 66.2 64.5 56.9 62.2 51.5 55.9 47.8 31.1 52.2 45.6 39.5 19.8 43.5 26.8 31.8 36.1 21.8 28.8 31.4 26.1 23.1 26.8 38.4 21.7 13.7
Factor
1 1
1 1 1
1 1 1 1 1 3 1 3
1 3 --3 3 2 2 2 2
Factor 1 = Absorption/Imaginative Involvement; factor 2 = Activities of Dissociated States; factor 3 = DepersonalizationiDereali zation; -indicates items that did not lead onto anvi factor at ZJc.05. Factors from principal components analysis of general population sample N = 1055.
pita1 populations. Because patients were not admitted to the hospital specifically for treatment of dissociative disorders, the sample was probably not skewed towards an unusually high frequency Table
3. Percentage of 299 psychiatric inpatients with high scores on the Activities of Dissociated States factor of the DES
Item Not recognizing friends or family Finding oneself in a place but unaware how one got there Finding unfamiliar things among one‘s belongings Finding oneself dressed in clothes one can’t remember putting on
% of Subjects scoring 30 or greater 6.3 7.9 17.2
6.5
of MPD. The fact that the patients completing the DES differed on the frequency of three clinical diagnoses compared with the noncompleters did not introduce an obvious major bias, because the groups did not differ on four other diagnoses. Additionally, the DES completers had a higher frequency of depression but lower frequencies of substance abuse and psychotic disorder not elsewhere classified, so there was no consistent pattern of difference between the two groups. Bearing in mind the need for replication, our findings suggest that both dissociative symptomatology and DSM-III-R dissociative disorders are common among psychiatric inpatients. It appears that a cutoff score of 30 for factor 2 items on the DES can predict the frequency of MPD in a clinical population. Further research is required to determine whether patients with high DES scores within nondissociative disorder diagnostic groups such as
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C. A. Ross et al.
mood disorders ment compared
have a different response to treatwith those with low DES scores. 10.
Supported by grants from the Manitoba Mental Health Research Foundation and the Manitoba Health Research Council
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