Formal Thought Disorder in Schizophrenia: Analytic Study

A Factor

Victor Peralta, Manuel J. Cuesta, and Jose de Leon The Thought, Language and Communication Scale (TLC) was studied in a sample composed of 115 DSM-III-R schizophrenic patients admitted to an acute inpatient unit. A principal component analysis with varimax rotation was performed to explore the possibility of the existence of syndromes within the formal thought disturbances. Seven factors were found to have eigen values greater than 1 and five showed appropriate internal consistency. The first factor, or disorganization factor, was close to the Scale for the Assessment of Positive Symptoms (SAPS) formal

T

HE FORMAL THOUGHT disorder is a core symptom in schizophrenia.’ Bleuler’ assumed thought disorder to be a fundamental and primary symptom, always present in schizophrenic patients. However, recent studies have shown that not all schizophrenic patients display formal thought disorders and that other psychotic patients, particularly manic, can also display them? The introduction of standardized assessment has increased the reliability of psychiatric symptom measurement. Two scales to measure formal thought disorders have gained wide use, the Thought, Language and Communication Scale (TLC)S and the Thought Disorder Index (TDI).6 The TLC was developed using a “strictly empirical or observational approach,” and includes 18 categories of formal thought disturbances obtained from the classical descriptions. Good interrater7.8 and test-retest reliability have been shown. Factor analysis is a suitable instrument for exploring the existence of syndromes made by intercorrelated symptoms. Several studies, using this methodology, have shown that the classification of thought disturbances into only positive and negative thought disorders is too simplistic. The TDI, which does not include the negative type of formal thought disturbances, has also shown that positive formal thought disturbances are not a homogeneous group of symptoms, rather they tend to cluster in several factors.“‘,” Andreasen and Grove9 described three TLC factors that accounted for 44% of the variance. Fluent disorganization (close to positive formal thought disorder), emptiness

COWrehensive

thought disturbance subscale. The second, or negative factor (perseveration, poverty of speech and content), was moderately correlated with poor premorbid functioning and poor response to neuroleptic treatment. The third and fourth factors were, respectively, formed by stilted speech plus word approximations, and neologisms plus clanging. The fiih factor (distractibility and blocking), as well as the first two factors, were correlated to the Scale for the Assessment of Negative Symptoms (SANS) attention subscale. Copyright 0 1992 by W.B. Saunders Company

(close to negative formal thought disorder), and linguistic control, respectively, accounted for 25%, IO%, and 9% of the variance. In this report, a factor analysis of the TLC is performed to explore the possibility of the existence of syndromes within the formal thought disturbances. The relation of these syndromes with other clinical variables is investigated. METHOD

Patients The sample comprised 115 schizophrenic patients admitted consecutively to an acute inpatient unit. Patients were diagnosed by one of the authors (V.P.) using DSM-III-R” criteria and a semistructured interview designed for schizophrenic patients.” The frequency of the types was 55% paranoid, 17% disorganized, 16% undifferentiated, 7% residual, and 6% catatonic. Males and females accounted for 69% and 31% of the patients, respectively. The mean age was 35.7 years (SD 12.3). and the average years of education was 9.0 (SD 3.7). The mean duration of illness and onset of age were 10.2 years (SD X.2) and 25.3 years (SD 8.4). respectively. The mean number of hospitalizations was 4.7 (SD 4.5). A more thorough description of the sample has been published.” Patients were taking neuroleptics and biperiden hydrochloride. All patients were treated with this anticholinergic to diminish the possibility of akinesia as a contributor to negative symptoms. The response to neuroleptic treatment

From the Medical College of Pennsylvania, Eastern PennTlvania Psychiatric Institute, Philadelphia, PA. This work was completed at the Psychiatric Unit of the “Virge~l de/ Car&o” Hospital, Pamplona, Spain. Address reprint requests to Jose de Leon, M.D., Medical College of Pennsylvania IEPPI, 3200 Henn; Ave. Philadelphia, PA 19129. Copyright 0 1992 by W B. Saunders Company 0010-440X/9213301-00019$03.0010

Psychiatry, Vol. 33, No. 2 (March/April), 1992: pp 105-110

105

106

PERALTA, CUESTA, AND DE LEON

was measured by the efficacy index rated 1 to 4 (unchanged to marked improvement).” The premorbid functioning was measured in a similar way from 1 (excellent) to 4 (very poor) following Global Assessment of Functioning (GAF) ratings.‘* (A GAF > 70 corresponded to a 1; a GAF between 51 and 70 corresponded to a 2; a GAP between to 31 to 50 corresponded to a 3; and a GAP < 30 corresponded to a 4.) The scale described by Strauss and Carpenter16 was used to assess prognosis. The Scale for the Assessment of Negative Symptoms (SANS)” and of the Scale for the Assessment Positive Symptoms (SAPS)‘* were used to measure schizophrenic symptoms.‘4

bath: the rij, which corrects for the item number, is also included. The Pearson r correlation was used to calculate the relationship between different types of formal thought disturbances (Table 2) and the association between the factor scores (obtained by regression) with other clinical variables. Due to the great number of correlations, a limit of P < .Ol was chosen as significant. The t test was used to explore the relationship between sex and the factors. The interrater reliability was measured by the intraclass correlation coefficient.*’

Assessment of Formal Thought Disturbances

RESULTS

The TLC was scored using information from two clinical interviews of at least 45 minutes’ duration conducted during the first 3 days of admission. The highest scores from both interviews were selected. The TLC was assessed by two of the authors (V.P. and M.J.C.). The interrater reliability was calculated in 33 patients who were assessed together (Table 1).

Frequency and Inter-raterReliability Only 14% of the patients showed no formal thought disorder. Most of the TLC items were frequent, and only five (clanging, neologisms, echolalia, stilted speech, and self-reference) were present in less than 10% of the patients (Table 1). The intraclass correlation coefficient (ICC) was excellent (> 30) for the global score and four items, good (.61-.79) for nine items, moderate (.41-.59) for three items, and low ( < .40) for two infrequent items (Table 1). The most frequent items showed an excellent or good interrater reliability.

Statistics The Statistical Package for Social Sciences” was used to perform principal component factor analyses with varimax rotation. The number of factors was determined by an eigen value greater than 1. The items that weighted greater than .40 were selected to make subscales. The internal consistency of the scales derived from the factors was calculated using Cronbach’s alpha. Since this index is influenced by the number of scale items, a modification described by Cron-

Table 1. Frequency, Severity, and Interrater Reliability of TLC Items in Schizophrenic Patients Frequency

1%)

Severity (mean)

ICC

TLC Items Author:

ON

Sample size:

115

42

DSM-3R

Diagnostic criteria:

Andreas&

Andreasen’

Our

Andreasen4

Davis?

50

115

42

42

33

RDC

RDC

DSM-3R

RDC

DSM-3

DSM-3R

Our

Poverty of speech

50

29

30

1.oo

.‘I?

.94

.74

Poverty of content

66

40

28

1.41

.76

1.81

.73

Pressure of speech

20

27

20

.32

.36

1.13

.86

Distractible speech

41

2

6

.77

.02

.68

.56

Tangentiality

57

36

20

1.09

55

1.20

.78

Derailment

50

56

62

1.09

1.20

1.48

.88

Incoherence

40

16

30

.89

.33

.51

.93

lllogicality

67

27

30

1.54

.42

1.14

.79

Clanging

8

0

4

.13

.oo

.07

.79

Neologisms

4

2

0

.07

.02

.06

.42

Word approximations

18

0

6

.30

.oo

.19

.15

Circumstantiality

36

4

16

.69

.04

1.50

.44

Loss of goal

50

44

30

1.03

.71

1.09

.68

Perseveration

45

24

24

.98

.13

.38

.73

Echolalia

6

4

0

.I2

.ll

.07

.64

Blocking

26

4

0

.57

.06

.43

.69

Stilted speech

10

2

2

.I7

.09

.02

.89

Self-reference

9

13

0

.16

.27

.I6

.33

Global rating

86

91

2.11

.85

Abbreviation: ICC, intraclass correlation coefficient.

1.8

FORMAL THOUGHT

DISORDER IN SCHIZOPHRENIA

107

Table 2. Factor Analysis and internal Consistency of the Derived Subscales Eigen Factor

1st

V.dues

(%I

4.0

22.4

Disorganization

2nd

2.1

12.0

Negative 3rd

1.5

Internal

Variance

8.6

Item

Weight

Derailment

.85

Loss of goal

.75

Tangentiality

.74

lllogicality

58

Circumstantiality

.55

Incoherence

.42

Poverty of content

.89

Poverty of speech

.79

Perseveration

.64

Stilted speech approximations

.82

Idiosyncratic 4th

1.4

8.1

Referential 7th

rij

.78

.37

.70

.44

.55

.38

58

.41

.50

.34 .20

Neologisms

.82

Clanging

.79

1.3

Blocking

.86

Distractible speech

.74

6.5

Self-reference

.80

.33

5.8

Echolalia Pressure of speech

.69 .91

-

7.8

Attentional 6th

Cal

.81

Semantic 5th

Consistency

1.1 1.0

Verbosity Abbreviations: Cal, Cronbach’s alpha; rij, modified Cal to correct for number of items.

Factor Analysis

Seven factors had an eigen value greater than 1 and they explained 71% of the variance (Table 2). All the TLC items had a weight greater than .40 in any of the factors. The first factor includes derailment, loss of goal, tangential@, illogical thinking, circumstantiality, and incoherence. It could be called disorganization factor, because it reflects thinking disorganization.y%2’ The second factor is composed of poverty of speech and content, and perseveration. It could be considered as a negative factor, because it includes the most important items of the SANS alogia subscale plus perseveration. We have named the third factor idiosyncratic, because it is formed by the stilted speech and word approximations which reflect an idiosyncratic way of using the language. Neologisms and clanging weight in the fourth factor probably indicate an anomaly of the meaning of words; therefore, it could be labeled as a semantic factor. Since the fifth factor includes distractibility as well as blocking, and is correlated with the attention disturbances measured by the SANS (Table 3), it could be designated as an attentional factor. Self-reference and echolalia constituted the sixth factor or referential factor.

The seventh factor, verbosity, was only composed of pressure of speech. Internal Consistency of the Subscales Derived From the Factors

The internal consistency was acceptable for the first five subscales. The Cronbach’s alpha Table 3. Correlation Between TLC Factors and SAPS/SANS Subscales Factors 1

2

3

4

DIS

NEG

ID10

SEM

5 ATTEN

6

7

REF

VER

-.16

-.17

Hallucinations

-.05

-.32*

.03

.08

.I1

Delusions

-.09

-.43t

.14

.I2

-.03

Bizarre behavior

-.ll

.19

.08

.I7

.07

.13

.06 .14

.06 -.17

Positive thought disorder

.68t

-.OO

.27*

.20

.36t

.17

.18

-.31t

.22*

.25*

.22*

.06 -.09

.04

.16 -.04

SAPS Global score Affective flatten-.lO

.64t

p.05

Alogia

ing

-.19

.62t

-.09

-.04

Avolition-apathy

-.07

.42t

p.16

-.I3

-.06

.03

.05

.50t

-.04

-.18

-.14

.Ol

.43t

.ll

-.ll

Anhedonia-asociality

-.12

Attention

.30t

.24* -.07

.07

.04

.41t

.13

.I5

.20

.14

.02

NEG. negative;

IDIO,

.15

SANS Global score Abbreviations:

-.05

.68t

-.12

DIS, disorganization;

p.04

idiosyncratic; SEM, semantic; ATTEN. attentional; REF, referential; VER, verbosity. “P < .Ol; t/J < ,001.

108

PERALTA, CUESTA, AND DE LEON

was greater than 5, and the rij, which corrects for the number of items was between .30 and .40 (Table 2). The sixth factor had a low eigen value and the subscale internal consistency was also too low. The possibility that this factor is an artifact is supported by the lack of significant correlation of the self-reference with echolalia. Self-reference was not significantly correlated with any other thought disturbance. Relationship of the Factors and Clinical Variables

The negative factor was associated with poor premorbid functioning (r = .26, P < .Ol), lower education (r = -.35, P < .OOl), poor response to the neuroleptics (r = -.36, P < .OOl), and total score obtained from the Strauss and Carpenter’s prognostic scale (r = -.28, P < .Ol). The relationship between the attentional factor and duration of the illness (r = -.22, P < .Ol) was the only other significant correlation with clinical variables. No sex differences were significant. It must be remembered that each of these correlations are significant, but account only for approximately 10% of the variance. Table 3 shows the correlations with the SANS and SAPS subscales. The first factor, the positive factor, was strongly associated with the positive formal thought disturbances and less with the attention subscale. The second factor, the negative, was correlated with all SANS subscales. The fifth factor, the attentional, significantly correlated with the positive formal thought disturbances, alogia, and attention. The association with alogia is due to the inclusion of blocking in this subscale. DISCUSSION

Frequency and Interrater Reliability

The frequency and severity of the different types of formal thought disturbances in this study were higher than in Andreasen’s sample.9 This is probably due to her use of different diagnostic criteria, the Research Diagnostic Criteria (RDC). Davis et a1.8 found severities similar to ours, when using DSM-III criteria, which closely parallels DSM-III-R (Table 1). The interrater reliability was similar to that

described by Andreasen7 and Davis et al.’ and there was concordance in items that were less reliable. Classification of the Formal Thought Disturbances

Andreasen and Grove’ found only three TLC factors, but 50 of their 100 patients were not RDC schizophrenic, being manic or schizoaffective. The disorganization, or positive factor, and the negative factor seem to be similar in the two studies. When the results from the TDI, which does not include negative disorders, have been factor analyzed,” they also showed several factors. The most important type of formal thought disorders are those included in the disorganization factor,9~“~Uwhich explained almost a fourth of the variance. This group of formal thought disorders is close to what Bleuler named “loss of associations.” This factor was not associated with delusions and hallucinations and did not show an association with good response to medication. It may be worthwhile to slightly modify the positive formal thought disturbances of the SAPS, including the loss of goal, and excluding clanging, pressure of speech, and distractibility. The former is frequent and shows high interrater reliability and the latter are less frequent and seem to measure other dimensions. The second factor of importance, the negative factor, justifies its name by the association with the SANS subscales, poorer premorbid functioning, and poorer response to treatment. It also showed a modest negative relationship with delusion and hallucinations. It can be suggested to modify the SANS alogia subscale to exclude blocking, and include perseverations. Blocking was not correlated to poverty of speech and content. Perseverations have been included by Kay et a1.24as a negative symptom and it has been considered as a sign of frontal lobe dysfunctier? or the linguistic expression of a tendency to persevere in different fields that can be found associated with lesions of this lobe.26 Formal thought disturbances have been hypothesized as being related to frontal dysfunction. More recently, Liddle23,28has suggested that negative

FORMAL THOUGHT

109

DISORDER IN SCHIZOPHRENIA

symptoms (affective flattening and poverty of speech) would be a sign of dorsolateral prefrontal dysfunction and the disorganization symptoms (thinking disorganization, poverty of content, and inappropriate affect) would be a sign of basal prefrontal dysfunction. The rest of the thought disorder factors seem less important and less prevalent. Only the attention factor showed a relationship with the clinical symptoms measured by the SANS and SAPS. The SANS attention subscale was significantly correlated with three types of formal thought disorder (disorganization, negative factors, and attentional factors). This relationship could be interpreted in two ways: (1) the three types of formal thought disorders have disturbance of attention as common underlying physiopathological basis. This interpretation appears unlikely due to the heterogeneity of the thought disturbances. (2) The SANS attention subscale does not measure a homogenous phenomena. Several findings support this interpretation. Attention is a complex concept that involves many phenomena and can be altered by many different physiopathological disturbances.” Different measures of attention show different associations with positive and negative symptoms’” and the SANS attention subscale has been shown to be correlated with positive and negative symptoms.‘4.“~3”~“’ Although Bleuler’ described the relationship between formal thought and attention disturbances, it is not clear whether attention disturbances precede thought disturbances3’ or whether attention disturbances are secondary to disturbances of thought.

Future Research

Replication of these factors in other large schizophrenic samples is needed. The first two factors can be replicated without great variations, because they have already appeared in the literature. Brain imaging studies are needed to verify whether or not these factors are associated with dysfunction at different areas of the frontal lobe. The use of a reliable and sophisticated instrument such as the TLC will contribute to the understanding of the relationship of psychiatric syndromes and the brain. Longitudinal studies to control the effect of neuroleptics and the illness phase are clearly needed, as it is impossible to distinguish the influence of neuroleptic treatment on our results. The study of nontreated schizophrenic patients would provide less contaminated data, but may be difficult to attain. Studies have shown that remission of the formal thought disturbances is not totaL3’ as a significant number of schizophrenics show residual “positive” formal thought disturbances.14 This suggests that the presence of formal thought disturbances carries a poor prognosis.34,35 The relationship between the formal thought disturbances and attention appears to be an interesting research pathway.“6 Longitudinal and cross-sectional studies to understand the connections between the different thought and attention disturbances could significantly contribute to the understanding of the pathophysiology of these and all schizophrenic symptoms.

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25. Buckingham HW. Perseveration in aphasia. In: Newman S, Epstein R (eds): Current Perspectives in Dysphasia. New York, NY: Churchill Livingstone, 1985:113-154. 26. Bilder RM, Goldberg E. Motor perseverations in schizophrenia. Arch Clin Neuropsychol 1987;2:195-214. 27. Kleist K. Schizophrenic symptoms and cerebral pathology. J Ment Sci 1970;106:246-255. 28. Liddle PF. Schizophrenic syndromes, cognitive performance and neurological dysfunction. Psycho1 Med 1987;17: 49-57. 29. Cornblatt BA, Lenzenweger MF, Dworkin RH, Erlenmeyer-Kimung L. Positive and negative schizophrenic symptoms, attention and information processing. Schizophr Bull 1985;11:397-408. 30. Knight RA, Elliott DS, Roff JD, Watson CG. Concurrent and predictive validity of components of disordered thinking in schizophrenia. Schizophr Bull 1986;12:427-446. 31. Walker EF, Harvey PD, Perlman D. The positive/ negative symptom distinction in psychoses. A replication and extension of previous findings. J Nerv Ment Dis 1988;176:359-363. 32. Harvey PD, Earle-Boyer EA, Levinson JC. Cognitive deficits and thought disorder: A retest study. Schizophr Bull 1988;14:57-66. 33. Spohn HE, Coyne L, Larson J, Mittleman F, Spray J, Hayes K. Episodic and residual thought pathology in chronic schizophrenics: effect of neuroleptics. Schizophr Bull 1986;12:394-407. 34. Marengo JT, Harrow M. Schizophrenic thought disorder at follow-up. A persistent or episodic course? Arch Gen Psychiatry 1987;44:651-659. 35. Kay SR, Murrill LM. Predicting outcome of schizophrenia: significance of symptom profiles and outcome dimensions. Compr Psychiatry 1990;31:91-102. 36. Holzman PS, Bivens LW, Bower GH, Campos J, Carpenter P, Ekman P, et al. A national plan for schizophrenic research: basic behavioral sciences. Schizophr Bull 1988;14:413-426.