The Subjective Experience of Deficits in Schizophrenia

The Subjective Experience in Schizophrenia

of Deficits

Peter F. Liddle and Thomas R.E. Barnes The disorganization and impoverishment of mental activity in chronic schizophrenia are usually inferred from observation of behavior. This paper describes a rating scale for the assessment of Subjective Experience of Deficits in Schizophrenia (SEDS), designed to measure subjective experience of disorganization or impoverishment of mental activity. In a study of 52 long-term schizophrenic inpatients, it proved possible to rate these experiences with satisfactory interrater reliability. The prevalence of subjective awareness of deficits was high. The pattern of relationships between subjective experience of deficits and other aspects of psychopathology indicated that various pathological processes occurring in schizophrenia contribute to the experience of disorganized or impoverished mental activity. The findings suggest that exploration of subjective experience of deficits can help delineate the nature of schizophrenic phenomena, and in addition might provide a basis for helping chronic schizophrenic patients develop appropriate coping strategies. o 1988 by Grune & Stratton,

CHIZOPHRENIC

Inc.

PATIENTS

suffer disorganization and impoverishment of

S thinking, emotion and perception. Some of these psychological deficits, such as

loosening of associations and flattening of affect, were regarded by Bleuler’ as characteristic of schizophrenia. Some, such as impaired concentration and anhedonia, are common in other psychiatric illnesses, and hence are of limited value in the process of diagnosis. Irrespective of their specificity for schizophrenia, these psychological deficits can exert a strong influence on a patient’s occupational and social adjustment. Reliable assessment of these deficits is potentially important in charting the course of the illness, in monitoring response to treatment, in detecting impending relapse, and in research into the nature of schizophrenia. Because psychological deficits are often associated with impairment of behavior and performance, the occurrence of these deficits can be inferred from the observation of behavior and the measurement of performance. However, the validity of such inferences is uncertain because a variety of different mental states might, in principle, be associated with a particular abnormality of observed behavior or performance. A more reliable assessment of psychological deficits is likely if both subjective and objective measures are taken into account. Recent attempts by Crow’ and Andreasen3 to elucidate the psychological deficits occurring in schizophrenia in terms of the positive-negative dichotomy have relied largely on the recording of observed deficits. In contrast, Huber4 has identified a “non-characteristic defect state” in schizophrenia delined largely on the basis of subjectively experienced abnormalities. At this stage, the relationship between Huber’s “non-characteristic defect state” and Crow’s Type 2 or Andreason’s “negative schizophrenia” requires further clarification. Andreasen’s Scale for the Assessment of Negative Symptoms (SANS)’ includes

From the Department of Psychiatry, Charing Cross & Westminster Medical School, London. Address reprint requests to Peter F. Liddle, B.M. B.Ch. B.Sc. Ph.D., MRCPsych, Academic Unit, St. Bernards Hospital, Uxbridge Rd. Southall, Middlesex, UBl 3EU. England. o 1988 by Grune & Stratton, Inc. 0010-440X/88/2902-0009$03.00/0 Comprehensive

Psychiarry,

Vol. 29, No. 2 (March/April),

1988: pp 157- 164

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LIDDLE

158

AND

BARNES

a single subjective item in each of its five subscales. In a preliminary study of the subjective experience of deficits, LiddIe found that the subjective items of SANS can contribute usefully to assessment of deficits, but more specific questions are necessary. This paper describes a rating scale for the assessment of subjective experience of deficits in schizophrenia (SEDS) constructed on the basis of experience gained in that preliminary study, supplemented by the interpretation of Huber’s basic symptoms provided by Koehler and Sauer.’ This scale rates only subjective experiences and in general, should be used in conjunction with a rating of observed behavior. The aims of the study reported here are: the assessment of the interrater reliability of the items of the scale; the determination of the prevalence of these items in a population of chronic schizophrenic patients; the examination of the relationship of subjective experience of deficits to other aspects of psychopathology; and the determination of the stability of these items over a period of 3 months. DESCRIPTION

OF THE SCALE

SEDS consistsof 21 items representing patients’ experience of deficits (see Table 1). These items are defined in a glossary which is available on request from the authors. Items are arranged in five groups: abnormal thinking and concentration; Table

1.

Prevalence,

Interrater

Reliability

for Severity,

and Persistence

of SEDS

Items.

Prevalence

Interrater reliability

Persistence

(%)

(K)

(%I

29 29 29 13 15 21

0.85 0.78 0.72 0.71 0.69 0.82

45 67 83 33 67 80

12 19 29 12

0.80 0.68 0.81 0.85

50 75 86 67

25 31 40

0.75 0.81 0.91

33 30 85

Perception Distorted special sensation Distorted somatic sensation Distorted visceral sensation Abnormal experience of the brain

6 23 17 10

0.94 0.90 0.53 0.65

0 0 33 100

Strain Intolerance Intolerance Intolerance

of impersonal of people of novelty

15 19 13

0.64 0.71 0.65

33 43 40

Miscellaneous Disturbance

of voluntary

19

0.75

100

Thinking Poor concentration Distractibility Absence of thought Slowed thinking Speeded thinking Difficulty remembering Emotion Labile mood Reduced range of emotion Anhedonia Inability to feel intimacy Drive/Energy Lack of motivation Lack of interests Lack of energy

stress

movement

Prevalance is % of cases definitely experiencing the item; Interrater reliability is expressed as weighted Cohen’s Kappa; Persistence is % of those cases definitely experiencing the item who report definite experience of the same item 3 months later.

SUBJECTIVE

DEFICITS IN SCHIZOPHRENIA

159

disturbance of affect; impaired will and decreased energy; disturbance of percep-

tion;andintolerance ofstress. The ratings are made on the basis of a semi-standardized interview. For each item there is a specified probe question. Whenever appropriate the interviewer must ask further questions to permit a judgment of whether or not the patient’s experience corresponds to the relevant experience defined in the glossary. The interviewer must judge whether or not the relevant experience is outside the range of normal experience. Inference based on observed behavior should be avoided. The interviewer must also ask further questions to assess the disruption of activity perceived by the patient and the distress associated with the experience. The occurrence of the experience, perceived disruption, and distress are assessed separately and then used to assign a score for overall severity. Occurrence, disruption, and distress are rated 0 if absent, I if definitely present, and 8 if the interviewer is uncertain. Overall severity is rated on a scale of 0 to 4 as follows: 0 = absent. 1 = questionable. It is uncertain if the relevant experience is outside the range of normal experience. 2 = mild. Awareness of the symptom is present occasionally without either substantial disruption of activities or marked distress. 3 = moderate. Awareness of the symptom is present frequently, or the symptom is associated with substantial disruption of activities, or with marked distress, but neither disruption nor distress is sufficient to warrant a rating of 4. 4 = severe. Disruption is such that efficiency of most relevant activities is greatly reduced (e.g., does not watch television or read at all because of poor concentration; no active interaction with family because of lack of ability to feel intimacy), or distress is persistent and intolerable (e.g., sufficient to lead to suicidal ideas). PATIENTS

AND METHODS

Patients: All 57 inpatients satisfying DSM-III criteria’ for schizophrenia from three wards, two long-stay wards and a rehabilitation ward, at Horton Hospital, were approached. Two patients refused to participate in the study, two patients were virtually mute, and one patient of foreign origin could not communicate adequately in English. The remaining 52 patients agreed to participate in the study. They comprised 31 males and 21 females. Their mean age was 58 years, and mean duration of illness was 28 years. Forty-nine were receiving antipsychotic medication, and 39 were also receiving anticholinergic medication.

Assessment of Psychopathology: SEDS, and the Manchester Scale’ were administered to the 52 patients. In order to assess interrater reliability of SEDS, two raters made independent ratings on the basis of a single interview, in a subsample of 30 cases. The SEDS ratings were repeated after an interval of 3 months, in 30 cases, to allow an estimate of the stability of the SEDS items over time.

Statistical Analysis: For each item, interrater agreement was quantified using Cohen’s weighted kappa,‘O which is a measure of correlation between the ratings of the independent observers, making allowance for chance agreement expected on the basis of the frequency of occurrence of the item. A measure of the stability of the items over time was calculated by expressing the number of cases in which the item was rated definitely present (score >l) at both the interviews, as a percentage of the number of cases in which the item was rated definitely present at the first interview.

LIDDLE AND BARNES

160

In an investigation of the relationship between awareness of deficits and other aspects of psychopathology, the results will depend on the breadth of psychopathology included in the items entered into the analysis. Individual SEDS items measure relatively specific aspects of psychopathology. An analysis of correlations with a comprehensive set of similarly specific items embracing a wide range of aspects of psychopathology, would entail the computation of a large number of correlation coefficients and it would be impossible to distinguish true correlations of moderate strength from correlations arising by chance. Therefore, in an exploratory study, it is appropriate to use relatively broad units of analysis. Items of the Manchester scale are appropriate for this purpose. Most Manchester items embrace a moderately broad range of distinguishable aspects of psychopathology. For example, the single score for delusions ignores distinctions between different types of delusions. In the case of SEDS, subscale summary scores providing an overall measure of particular classes of subjective experience were derived by adding scores for severity of the individual items within each subscale. Pearson correlations between SEDS subscale summary scores and Manchester Scale items were determined. Pearson correlations between the various SEDS subscale scores were also calculated. Statistical significance was assessed using two-tailed tests. While it is appropriate to use broad units of analysis in an exploratory study, this strategy suffers from the disadvantage that a strong correlation between a specific SEDS items and some other aspect of psychopathology might be obscured within a relatively weak correlation between the relevant subscale score and that other aspect of psychopathology. Therefore, in cases where significant associations between subscale scores and Manchester Scale items were found, the correlations of the individual items in the subscale with the relevant Manchester item were examined. The relationship between subjective experience of deficits and current medication was examined by calculating the Pearson correlation between SEDS subscale scores and current dose of neuroleptic medication expressed in chlorpromazine equivalents.”

RESULTS

AND DISCUSSION

Interrater reliability for rating of severity of individual SEDS items was satisfactory. The values of Cohen’s weighted kappa ranged from 0.94 for distorted special sensation to 0.53 for distorted visceral sensation. Since the estimation of severity entails a judgement whether or not the reported experience lies outside the range of normal experience, and in addition, an assessment of duration, disruption of activity and distress associated with the patient’s experience, the generally high levels of interrater agreement indicate that the majority of patients were able to give a comprehensible account of their experience of deficits. Subjective experience of deficits was common in this group of patients. Eightyfive percent of patients were definitely aware of at least one of the SEDS items. The prevalence of the individual items is shown in Table 1. Deficits of drive and energy were the most prevalent items, while awareness of various disturbances of thinking was also common. Awareness of deficits was approximately equally prevalent among males and females. There was a tendency for awareness of deficits to decrease with increasing age. Ninety-three percent of the 28 patients aged under 60 years were rated definitely aware of at least one SEDS item, and the mean number of items rated definitely present for each patient was 5.7. Seventy-nine percent of the 24 patients aged 60 years or over were rated definitely aware of at least one SEDS item, and the mean number of items rated definitely present for each patient was 2.6. For 20 of the 21 items, the prevalence was higher in the younger group of patients. In the case of the subjective experience of poor concentration, distractibility, absence of thought, speeded thinking, difficulty remembering, anergia/fatiguability, and abnormal experience of the brain, the higher prevalence in the younger group was statistically significant at the level P < 0.05, according to the Mann-Whitney U Test. The only

SUBJECTIVE

DEFICITS

IN SCHIZOPHRENIA

161

item which was more prevalent in the older group was intolerance of novelty, but this difference was not statistically significant. The various items of SEDS differed greatly in their persistence over a 3 month period in this group of patients, all of whom were long-term inpatients in a relatively stable state. Table 1 shows that items such as absence of thought, difficulty remembering, anhedonia, lack of energy, abnormal experience of the brain, and awareness of disturbance of voluntary movement exhibit a very high degree of persistence. On the other hand, distorted special sensation and distorted somatic senstation did not persist in any of the patients. The very high interrater reliability for these two items makes it unlikely that the lack of persistence is an artifact produced by unreliable assessment. Thus, the evidence suggests that these perceptual distortions are transient phenomena, even during a chronic phase of the illness. The correlations of SEDS subscale summary scores with other aspects of psychopathology rated according to the Manchester Scale (Table 2) demonstrate that the severity of subjective awareness of deficits is related in a systematic manner to other schizophrenic psychopathology. However, none of the correlation coefficients exceeds 0.5, demonstrating that the Manchester Scale items account for only a minor proportion of the variance of SEDS subscale scores. Awareness of difficulties with thinking is associated with delusions, hallucinations, and incoherence of speech, but exhibits a negative correlation with poverty of speech. Perceptual distortions, despite their transience, exhibit a similar pattern of correlations. Calculation of the correlations between individual items of the SEDS perception subscale and delusions, hallucinations and incoherence of speech reveals that distorted somatic sensation was the individual item most strongly correlated with delusions (r = 0.46, P < O.OOl), hallucinations (r = 0.45, P < O.OOl), and incoherence of speech (r = 0.37, P = 0.004). The SEDS emotion subscale score, which does not include a contribution from a specific depression item, nonetheless exhibited a moderate correlation with depression. Calculation of correlations between individual items of the emotion subscale and depression revealed that the strongest correlation was that between anhedonia and depression (r = 0.39, P = 0.002). There was a statistically significant, but nonetheless relatively weak correlation

Table 2. Pearson Correlations Between SEDS Subscale Summary Scores and Other Aspects of Psychopathology. Rated According to the Manchester Scale. SEDS Subscale

Depression Anxiety Delusions Hallucinations Incoherence Poverty of speech Flattened affect Psychomotor retardation *P < 0.05.

fP < 0.01.

Thinking

Emotion

Drive/Energy

Perception

-0.1 1 -0.02 0.35* 0.301 0.32’ -0.32* 0.00 -0.16

0.32’ 0.05 0.22 0.04 0.13 -0.15 0.28* 0.14

0.32’ 0.09 0.21 -0.01 0.16 -0.04 0.19 0.17

-0.11 0.29’ 0.43t 0.33* 0.32* -0.24 -0.03 -0.14

Strain -0.04 0.36t 0.08 0.33’ 0.12 0.17 0.19 0.24

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LIDDLE AND BARNES

between the SEDS emotion subscale score and observed flattening of affect. Observed flattening of affect was more severe in the older patients whereas there was a greater awareness of deficits in the younger patients. In the group of 28 patients under the age of 60, the correlation between the SEDS emotion subscale score and observed affective flattening was 0.48 (P = 0.008). The SEDS subscale score for lack of drive/energy exhibited a pattern of correlations similar to that exhibited by the emotion subscale score. Lack of drive/energy was correlated with depression. Calculation of the correlations between individual items of the drive/energy subscale and depression revealed that the largest correlation was a correlation of 0.40 (P = 0.002) between lack of interests and depression. The SEDS strain subscale score, which is a measure of perceived inability to tolerate various forms of stress, was correlated with anxiety and also with hallucinations. Perceived inability to tolerate people was the individual item within the strain subscale most strongly correlated with anxiety (r = 0.38, P = 0.002). In contrast, hallucinations were more strongly associated with perceived inability to tolerate impersonal stress (r = 0.47, P -c0.001). Whereas the majority of substantial correlations between SEDS subscale scores and Manchester items were positive, there was a negative correlation between observed poverty of speech and the subscale for awareness of disordered thinking (Table 1). Possibly this negative correlation merely reflects a difficulty in eliciting subjective items in the presence of poverty of speech. To investigate this question further, correlations between all of the individual SEDS items and poverty of speech were calculated. Seventeen of the 21 correlation coefficients were negative, confirming a relatively nonspecific negative association between elicited subjective experience and observed poverty of speech. In contrast, poverty of speech was positively correlated with perceived inability to tolerate people (r = 0.35, P = 0.006) suggesting that one factor contributing to social withdrawal by schizophrenic patients is an attempt to cope with inability to tolerate interpersonal contact. This hypothesis receives further support from the existence of a similar correlation between perceived inability to tolerate people and observed flatness of affect (r = 0.35, P = 0.006). The pattern of correlations between subjective experience of deficits and other aspects of psychopathology suggests that these subjective experiences do not constitute a single syndrome, but rather arise from a variety of pathological processes. This is confirmed by an examination of the correlations between the various SEDS subscale scores (Table 3). There is a high correlation between the subscale comprising awareness of disorders of thinking and the perceptual disorder subscale, suggesting that the pathological processes underlying these experiences share features in common. Similarly, the strong correlation between the emotion subscale score and the drive/energy subscale score suggests overlap of the pathological processes generating the subjective experiences that contribute to these subscale scores. There was no substantial evidence for an association between current medication and the subjective experience of deficits. The correlation of each of the 21 SEDS items and each of the five SEDS subscale scores with current dose of antipsychotic medication and with use of anticholinergics was examined. Of the 52 correlation coefficients, only one was significant at the level P < 0.05, and that was a rather

SUBJECTIVE

DEFICITS

IN SCHIZOPHRENIA

Table 3. Pearson Correlations

163

Between

SEDS Subscale Summary

Scores.

SEDS Subscale Thinking

Emotion

Drive/Energy

Thinking Emotion Drive/Energy

1 0.462 0.33’

1 0.59$

1

Strain Perception

0.32* 0.623

0.19 0.31*

0.14 0.25

Perception

;.56$

Strain

1

*P < 0.05. tP
weak correlation of 0.29 (P = 0.04) between labile mood and current dose of antipsychotic medication. CONCLUSIONS

The high prevalence of subjective experience of deficits, and the correlations of these experiences with other aspects of schizophrenic psychopathology is consistent with Huber’s4 view that these types of subjective experience are an integral part of schizophrenia. The subjective experiences do not constitute a single syndrome, and it is probable that various pathological processes contribute to these experiences. This study did not address the question of the specificity of these experiences to schizophrenia, but it is well known that experiences such as difficulty with thinking, anhedonia, and lack of drive and energy occur in depressive illness. The finding that anhedonia and lack of drive and energy were correlated with depression in this group of chronic schizophrenic patients suggests a phenomenological similarity between depression in schizophrenia and depressive illness. Exploration of the subjective experience of deficits offers the possibility not only of helping delineate the nature of schizophrenic phenomena, but also of helping patients to develop appropriate coping strategies.‘* For example, the finding that perceived inability to tolerate people was correlated with observed poverty of speech and flatness of affect suggests that schizophrenic patients use withdrawal as a coping strategy. The patients’ awareness of difficulty with interpersonal stress provides a basis for helping him or her to utilize this coping strategy appropriately. REFERENCES 1. Bleuler E: Dementia Praecox or the Group of Schizophrenias, trans. J. Zinken. New York: International Universities Press, 1950 2. Crow TJ: Molecular pathology of schizophrenia: More than one disease process? Br Med J 280: I-9, 1980 3. Andreasen NC, Olsen S: Negative v. positive schizophrenia. Arch Gen Psychiatry 39:789-794, 1982 4. Huber G: Reine Defectsyndrome und Basisstadien endogener Psychosen. Fortschr Neural Psychiatr 34:409-426, 1966 5. Andreasen NC: Negative symptoms in schizophrenia: definition and reliability. Arch Gen Psychiatry 39:784-788, 1982 6. Liddle PF: Do subjective symptoms underlie observable deficits in schizophrenia? Third Bi-annual Winter Workshop on Schizophrenia, Schaldming, Austria, 1986 7. Koehler K, Sauer H: Huber’s Basic Symptoms: Another Approach to Negative Psychopathology in Schizophrenia. Compr Psychiatry 25:174-182, 1984

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8. American Psychiatric Association: Diagnostic and statistical manual of mental disorders, (third edition). Washington DC, American Psychiatric Association, 1980 9. Krawiecka M, Goldberg D, Vaughan M: A standardized psychiatric assessment for rating chronic psychotic patients. Acta Psychiatr Stand 55:299-308, 1977 10. Cohen J: Weighted Kappa: Nominal Scale Agreement with Provision for Scales Disagreement or Partial Credit. Psycho1 Bull 70:213-220, 1968 11. Davis JM: Comparative doses and costs of antipsychotic medication. Arch Gen Psychiatry 33:858-861, 1976 12. Bilker W, Brenner HD, Gerstner G, et al: Self-healing strategies among schizophrenica: attempts at compensation for basic disorders. Acta Psychiatr Stand 69:373-378, 1984