- Email: [email protected]
Measuring thought disorder with clinical rating scales in schizophrenic and nonschizophrenic patients
313
Psychiatry Research, 15, 3 13-318 Elsevier
Measuring Thought Disorder With Clinical Rating Scales in Schizophrenic and Nonschizophrenic Patients Dale M. Simpson Received
September
and Glenn
C. Davis
24, 1984; revised version received May 3, 1985; accepted May 13, 1985.
Abstract. The distinction between disorders of thought structure and disorders of thought content in a diagnostically heterogeneous psychiatric population was empirically tested using factor analysis applied to the item scores on two common clinical rating scales, the Brief Psychiatric Rating Scale and Andreasen’s Thought, Language, and Communication Scale. The factor structure supported the separation of disordered thinking into disorders of thought content and disorders of thought structure or communication. Additionally, our results indicate that both aspects of disordered thinking are present in schizophrenic and manic patients; neither is specifically characteristic of schizophrenia. Indeed, disordered thought structure appears to be more common or worse in the manic patient than in the schizophrenic patient. Key Words. Thought
disorder,
schizophrenia,
mania, factor analysis.
presence and significance of disordered thinking in the phenomenology of schizophrenia as well as mania and depression has become a topic of much recent interest (Andreasen et al., 1974; Andreasen and Powers, 1975; Harrow and Quinlan, 1977; Andreasen, 1979b; Crow, 1980a, 1980b; Harrow et al., 1983; Silberman et al., 1983). Historically, the psychiatric literature frequently separates thought disorder into disorders of thought structure and disorders of thought content. Disordered thought structure results either from abnormalities in the pattern of speech such as loss of grammar and word salad or from abnormalities in the pattern of thinking such as loosening of associations and illogicality. Disordered thought content typically results from the presence in speech of delusional material and possibly hallucinations. In this sense, speech containing discussions of hallucinations represents abnormal thought content similar to discussions of any other delusion or false belief. Various rating scales have been used to measure disordered thinking in clinical populations. Two of these scales are used in the present study: the Brief Psychiatric Rating Scale (BPRS) (Overall and Gorham, 1962) and Andreasen’s Scale for the Assessment of Thought, Language, and Communication (TLC) (Andreasen, 1979a, 19796). The BPRS was originally developed as a rapid and reliable index of psychopathology for psychopharmacology research in schizophrenia. In its developThe
Dale M. Simpson, M.D.,
Ph.D., is Assistant Professor, Case Western Reserve University School of Medicine and Cleveland VA Medical Center, Glenn C. Davis, M.D., is Director, Psychiatry Research Program, Cleveland VA Medical Centerand Associate Professor, Case Western Reserve University School of Medicine. (Reprint requests to Dr. D.M. Simpson, VA Medical Center 1I(B), 10000 Brecksville Rd., Brecksville. OH 44141, USA.) 0165-1781/851$03.30
0 1985 Elsevier Science Publishers
B.V.
314 ment, a large number of rating items were reduced using factor-analytic techniques; thus, each of the items on the BPRS can be viewed as representing a separate factor. The presence of separate items for rating conceptual disorganization and unusual thought content supports the empirical separation between these two aspects of disordered thinking. However, despite the separate items for disordered thought content and thought structure on the BPRS, the two items have loaded together in subsequent factor-analytic studies, and thought disorder has frequently been measured clinically by taking the unweighted sum of scores from the items conceptual disorganization, unusual thought content, and hallucinatory behavior. This clustering of items was originally derived from factor analysis of BPRS data for schizophrenic populations (Overall et al., 1967). Subsequent factor-analytic studies of the BPRS in other schizophrenic groups have produced an identical thought disorder factor (Guy et al., 1975). The loading of both conceptual disorganization and unusual thought content on the same factor in these studies and the derived method of rating thought disorder fail to support the empirical separation of disorders of thought content from disorders of thought structure. This could result from the fact that the degree of correlation between these two aspects of thought disorder may vary with the psychiatric population under study. In a diagnostically heterogeneous population, rather than a purely schizophrenic population, there may be more symptomatic separation of abnormal thought content from abnormal thought structure. However, a previous study of a diagnostically heterogeneous population using the BPRS alone has also supported this linking of disordered thought structure and content (Dingemans et al., 1983). An alternative to the BPRS for the clinical rating of thought disorder, particularly structural thought disorder, is Andreasen’s TLC. The TLC is an observer-rated scale that has good interrater reliability and focuses on disorders of thought structure rather than thought content. TLC-rated symptoms of structural thought disorder can range from poverty of associations to derailment or illogicality. Andreasen’s TLC extends the BPRS item conceptual disorganization to multiple items for the assessment of structural thought disorder. The combination of the BPRS and the TLC would therefore seem to offer an improved basis for testing the empirical validity of the distinction between disordered thought structure and disordered thought content in a diagnostically heterogeneous psychiatric population. The present study addresses two questions: (1) To what extent does disordered thought structure separate from disordered thought content in factor analysis of simultaneous BPRS and TLC ratings of a diagnostically heterogeneous psychiatric population? (2) To what extent is disordered thought structure separate from disordered thought content in measurements based on these clinical rating scales in the three psychiatric diagnostic groups of schizophrenia, mania, and depression‘? As mentioned above, these three clinical groups have each been argued to exhibit disordered thinking. Using the BPRS and Andreasen’s TLC scale, we examined whether separate factors for disordered thought content and disordered thought structure would be produced by the analysis of combined clinical ratings on these two scales.
315 Methods The study used the 18-item BPRS (Overall et al., 1967; Guy et al. 1975; Dingemans et al. 1983) plus additional ratings of elated mood, motor hyperactivity, distractibility, helplessnesshopelessness, sexual preoccupation, and hallucinatory behavior. To these 24 items were added the 18 items from Andreasen’s TLC scale based on rating methods from a manual provided by the author. Two raters, both practiced in the use of the BPRS and TLC scales, independently rated 100 psychiatric patients with a variety of diagnoses. Assigned diagnoses based on DSMII1 criteria (American Psychiatric Association, 1980) were determined by chart review. Each patient was rated only once by each rater. The raters had no knowledge of chart diagnosis, which was determined by a third investigator who did not participate in clinical ratings. The patients included 42 diagnosed as schizophrenic, 11 as manic, 16 as depressive illness, 24 as personality disorder or substance abuse, and 7 with miscellaneous diagnoses. Iterated factor analysis with orthogonal varimax rotation was performed on the BPRS data alone and on the combination of BPRS and TLC data (BMDP, 1979 version). All factors accounting for at least 5% of the total variance in the data were included in the results. BPRS and TLC items with a factor score > 0.60 were considered as loading on the relevant factor and are reported below. This cutoff was selected because it resulted in at least three items loading on each factor and no items loading on more than one factor. Factor coefficients for the relevant items for each factor were used to generate mean factor scores for the population studied. Differences between these factor scores for the three clinical diagnostic groups of schizophrenia, mania, and depression were examined using analysis of variance with subsequent a posteriori comparisons based on Tukey’s w procedure (Sokal and Rohlf, 1969).
Results Factor analysis of the BPRS items, the mania rating items, and the items from Andreasen’s TLC resulted in two separate thought disorder factors. The first of these factors represents disordered thought structure derived largely from TLC items (Table 1) and accounts for the largest proportion of the total variance (24%). The items loading on this factor are the TLC items loss of goal, tangentiality, derailment, circumstantiality, illogicality, pressured speech, and incoherence and the BPRS items disorganized speech and distractibility. The second thought disorder factor loads on hallucinatory statements, hallucinatory behavior, and unusual thought content. This factor appears to measure solely disordered thought content and accounts for only 5% of the total variance. In addition to these two thought disorder factors, the analysis produced a mania factor, plus factors resembling those from previous BPRS factor-analytic studies. The mania factor is composed of two new scale items, elated mood and motor hyperactivity, plus the BPRS item excitement. The fourth, fifth, and sixth factors largely replicate the previously reported BPRS factors of anergia, hostilitysuspiciousness, and anxiety-depression. The fourth factor, termed the negative symptom factor, resembles the previous anergia factor and is composed of ratings for motor retardation, blunted affect, poverty of speech (from the TLC), and disorientation. The fifth factor is composed of ratings for uncooperativeness, hostility, and suspiciousness. The sixth factor is composed of ratings of anxiety, helplessnesshopelessness, and depressive mood. Differences between patients in the diagnostic categories of schizophrenia, mania,
316 and depression for each of the six factors were next examined using analysis of variance and a posteriori testing. Significant differences within these three diagnostic groups were found for the thought content disorder factor (F = 4.37; df 2, 62; p < 0.02) and the mania factor (F= 6.17; df 2,62;p < 0.0 1). A posteriori testing at an alpha of 0.05 demonstrated significant differences between schizophrenic and depressed patients but not between manic patients (means: 5.94 vs. 3.65 vs. 4.54, respectively) and either group. On the mania factor, manic patients differed significantly from both schizophrenic and depressed patients (means: 6.39 vs. 3.81 vs. 4.40, respectively). On the structural thought disorder factor, manic patients rated the highest followed by schizophrenic patients and depressed patients (means: 11.51 vs. 8.32 vs. 7.08, respectively), but these differences did not reach statistical significance. q
q
Table
1. Factor
analysis
of BPRS
and TLC Factor coefficient
Scale item Factor l-Disordered Loss of goal Conceptual
thought
structure
(24% of variance) 0.88
(TLC) disorganization
(BPRSi
0.85
Tangential
(TLC)
0.84
Derailment
(TLC1
0.83
Circumstantial lllogicality
(TLC)
Pressured
speech
Distractibility Incoherent
0.77
(TLC)
0.68
(added)
0.61 0.60
(TLC)
Factor a--Disordered
thought
Hallucinatory
statements
Hallucinatory
behavior
Unusual
thought
Factor 3-Mania Excitement
(BPRSI
0.87
(added)
0.81
(BPRSI
0.62
(6% of variance)
Motor
hyperactivity
0.68 0.68
(added)
Factor 4-Negative
symptoms
retardation
(14% of variance) 0.83
(BPRS)
affect
Poverty
of speech
Disorientation
0.78
(added)
Blunted
0.83
(BPRS)
0.70
(TLC)
(BPRS)
Factor 5-Hostility
0.60
& suspiciousness
Uncooperativeness
(8% of variance)
(BPRS)
0.87 0.88
(BPRS)
Suspiciousness Factor B-Anxiety Anxiety
(5% of variance)
(BPRS)
mood
Hostility
content
content
Elated
Motor
0.65
[TLC)
0.85
( BPRSi & depression
(4% of variance)
i BPRS)
0.78
Helplessness-hopelessness Depressive
mood
[BPRS)
(added)
0.80 0.63
317 Discussion Factor analysis of the BPRS and TLC items produced separate factors for disordered thought structure and disordered thought content in our diagnostically heterogeneous psychiatric population. The factor that accounts for the largest portion of the total variance in the data is derived largely from TLC items, but also contains the BPRS items conceptual disorganization and distractibility. This factor appears to be a very specific measurement of structural thought disorder. Its separation from both the mania factor and the disordered thought content factor argues that disordered thought structure is a separate dimension of psychopathology. Since poverty of speech is the only TLC item to load on any of the other five factors, the TLC seems to have high specificity for the measurement of structural thought disorder. Thus, our results indicate that the recently introduced TLC rating scale is highly specific for the measurement of structural thought disorder and does not measure the same clinical symptom complex as the previously described BPRS thought disorder factor, which nonselectively measures disordered thought structure and content. Either scale may have some advantages depending on the clinical application intended. The addition of six items for rating manic behavior to the 18-item BPRS produces a separate mania factor that contains two of the six new items, plus the BPRS item excitement. This is consistent with the recognition that the authors of the BPRS were trying to reduce clinical factors to a single item. However, the presence of only a single item for rating mania suggests that the original BPRS items may not be optimal for clinical ratings of manic populations. Examination of factor scores generated by the combined BPRS-TLC analysis indicates that two and perhaps three factors are of particular relevance in differentially characterizing schizophrenic, manic, and depressed patients. These three factors rated mania, disordered thought content, and disordered thought structure. As might be expected, manic patients produce the highest scores on the mania factor, with schizophrenic patients producing the lowest scores. Manic patients also show the highest scores on disordered thought structure, while depressed patients show the lowest scores. Schizophrenic patients show the highest scores on hallucinations and delusions (disordered thought content), with depressed patients showing the lowest scores. Curiously, although schizophrenic patients receive the highest rating on the negative symptom or anergia factor, they do not differ significantly from manic and depressed patients on this item; nor do depressed patients differ significantly from the other two groups on the depression-anxiety factor. The present results indicate that the addition of the TLC to the BPRS results in a major improvement in the assessment of disordered thought structure, without altering the other BPRS factors previously reported. The structural thought disorder factor accounted for the largest portion of the variance in a data set based on ratings of patients with a variety of psychiatric diagnoses. For the various groups, manic patients received the highest mean factor scores on this factor, with schizophrenic patients being second highest. Therefore, disordered thought structure, as measured by Andreasen’s TLC, may be more characteristic of manic patients than of schizophrenic patients, who show greater thought content disorder. The conceptual separation of structural thought disorder from thought content disorder seems relevant to the
318 clinical assessment of mixed psychiatric manic and schizophrenic patients. Acknowledgment.
The research
reported
populations,
was supported
particularly
by the Veterans
those containing
Administration
References Psychiatric Association. DSM-III: Diagnostic and Statistical Manual of Mental 3rd ed. APA. Washington, DC (1980). Andreasen, N.J.C. Thought, language, and communication disorders: I. Clinical assessment, definition of terms, and evaluation of their reliability. Archives of General Psychiatry, 36, 13 15 American
Disorders.
(1979a).
Andreasen, N.J.C. Thought. language, and communication disorders: II. Diagnostic significance. Archives of General Psychiatry, 36, 1325 (1979b). Andreasen, N.J.C., and Powers, P.S. Overinclusive thinking in mania and schizophrenia. British Journal
of Psychiatry,
125,452
(1975).
Andreasen, N.J.C., Tsuang, M.T., and Canter, A. The significance of thought disorder in diagnostic evaluations. Comprehensive Psychiatry, 15, 27 (1974). Crow, T.J. Molecular pathology of schizophrenia: More than one disease process? British Journai
of Psychiatry,
Crow, T.J. Positive Journal
of Psychiatry,
137, 66
(1980a).
and negative
schizophrenic
symptoms-The
role of dopamine.
British
137, 383 (1980h).
Dingemans, P.M., Frohn-de Winter, M.L., Bleeker, J.A.C., and Rathod, P. Across-cultural study of the reliability and factorial dimensions of the Brief Psychiatric Rating Scale (BPRS). Psychopharmacology, Guy, W., Cleary,
system.
80, 190 ( 1983).
P., and Bonato, R. R. Methodological implications of a large central data In: Boisser, J.R., Hippius, H., and Pichot, P., eds. Neuropsychopharmacology:
Proceedings of the IX Congress of the Collegium Internationale Neuropsvcho-pharmacologicum, Paris, 7-12 Ju/y, 1974. Excerpta Medica, Amsterdam (1975). Harrow, M., and Quinlan, D. Is thought disorder unique to schizophrenia? Archives General Psychiatry, 34, I.5 (1977).
of
Harrow, M., Silverstein, M., and Marengo, J. Disordered thinking: Does it identify nuclear schizophrenia? Archives of General Psychiatry, 40, 765 (1983). Overall, J.E., and Gorham. D.R. The Brief Psychiatric Rating Scale. Psychological Reports, 10,799 (1962). Overall, J.E., and Klett. C.J. Applied Multivariate Analysis. McGraw-Hill, New York (1972). Overall, J.E., Hollister, L.E., and Pichot, P. Major psychiatric disorders. Archives of General Psychiatry,
16, 146 (1967).
Sokal, R.R., and Rohlf, F.J. Biometry. W.H. Freeman & Co., San Francisco (1969). Silberman, E.K., Weingartner, H., and Post, R. Thinking disorder in depression. Archives General
Psychiatry,
40, 775 (1983).
of
Psychiatry Research, 15, 3 13-318 Elsevier
Measuring Thought Disorder With Clinical Rating Scales in Schizophrenic and Nonschizophrenic Patients Dale M. Simpson Received
September
and Glenn
C. Davis
24, 1984; revised version received May 3, 1985; accepted May 13, 1985.
Abstract. The distinction between disorders of thought structure and disorders of thought content in a diagnostically heterogeneous psychiatric population was empirically tested using factor analysis applied to the item scores on two common clinical rating scales, the Brief Psychiatric Rating Scale and Andreasen’s Thought, Language, and Communication Scale. The factor structure supported the separation of disordered thinking into disorders of thought content and disorders of thought structure or communication. Additionally, our results indicate that both aspects of disordered thinking are present in schizophrenic and manic patients; neither is specifically characteristic of schizophrenia. Indeed, disordered thought structure appears to be more common or worse in the manic patient than in the schizophrenic patient. Key Words. Thought
disorder,
schizophrenia,
mania, factor analysis.
presence and significance of disordered thinking in the phenomenology of schizophrenia as well as mania and depression has become a topic of much recent interest (Andreasen et al., 1974; Andreasen and Powers, 1975; Harrow and Quinlan, 1977; Andreasen, 1979b; Crow, 1980a, 1980b; Harrow et al., 1983; Silberman et al., 1983). Historically, the psychiatric literature frequently separates thought disorder into disorders of thought structure and disorders of thought content. Disordered thought structure results either from abnormalities in the pattern of speech such as loss of grammar and word salad or from abnormalities in the pattern of thinking such as loosening of associations and illogicality. Disordered thought content typically results from the presence in speech of delusional material and possibly hallucinations. In this sense, speech containing discussions of hallucinations represents abnormal thought content similar to discussions of any other delusion or false belief. Various rating scales have been used to measure disordered thinking in clinical populations. Two of these scales are used in the present study: the Brief Psychiatric Rating Scale (BPRS) (Overall and Gorham, 1962) and Andreasen’s Scale for the Assessment of Thought, Language, and Communication (TLC) (Andreasen, 1979a, 19796). The BPRS was originally developed as a rapid and reliable index of psychopathology for psychopharmacology research in schizophrenia. In its developThe
Dale M. Simpson, M.D.,
Ph.D., is Assistant Professor, Case Western Reserve University School of Medicine and Cleveland VA Medical Center, Glenn C. Davis, M.D., is Director, Psychiatry Research Program, Cleveland VA Medical Centerand Associate Professor, Case Western Reserve University School of Medicine. (Reprint requests to Dr. D.M. Simpson, VA Medical Center 1I(B), 10000 Brecksville Rd., Brecksville. OH 44141, USA.) 0165-1781/851$03.30
0 1985 Elsevier Science Publishers
B.V.
314 ment, a large number of rating items were reduced using factor-analytic techniques; thus, each of the items on the BPRS can be viewed as representing a separate factor. The presence of separate items for rating conceptual disorganization and unusual thought content supports the empirical separation between these two aspects of disordered thinking. However, despite the separate items for disordered thought content and thought structure on the BPRS, the two items have loaded together in subsequent factor-analytic studies, and thought disorder has frequently been measured clinically by taking the unweighted sum of scores from the items conceptual disorganization, unusual thought content, and hallucinatory behavior. This clustering of items was originally derived from factor analysis of BPRS data for schizophrenic populations (Overall et al., 1967). Subsequent factor-analytic studies of the BPRS in other schizophrenic groups have produced an identical thought disorder factor (Guy et al., 1975). The loading of both conceptual disorganization and unusual thought content on the same factor in these studies and the derived method of rating thought disorder fail to support the empirical separation of disorders of thought content from disorders of thought structure. This could result from the fact that the degree of correlation between these two aspects of thought disorder may vary with the psychiatric population under study. In a diagnostically heterogeneous population, rather than a purely schizophrenic population, there may be more symptomatic separation of abnormal thought content from abnormal thought structure. However, a previous study of a diagnostically heterogeneous population using the BPRS alone has also supported this linking of disordered thought structure and content (Dingemans et al., 1983). An alternative to the BPRS for the clinical rating of thought disorder, particularly structural thought disorder, is Andreasen’s TLC. The TLC is an observer-rated scale that has good interrater reliability and focuses on disorders of thought structure rather than thought content. TLC-rated symptoms of structural thought disorder can range from poverty of associations to derailment or illogicality. Andreasen’s TLC extends the BPRS item conceptual disorganization to multiple items for the assessment of structural thought disorder. The combination of the BPRS and the TLC would therefore seem to offer an improved basis for testing the empirical validity of the distinction between disordered thought structure and disordered thought content in a diagnostically heterogeneous psychiatric population. The present study addresses two questions: (1) To what extent does disordered thought structure separate from disordered thought content in factor analysis of simultaneous BPRS and TLC ratings of a diagnostically heterogeneous psychiatric population? (2) To what extent is disordered thought structure separate from disordered thought content in measurements based on these clinical rating scales in the three psychiatric diagnostic groups of schizophrenia, mania, and depression‘? As mentioned above, these three clinical groups have each been argued to exhibit disordered thinking. Using the BPRS and Andreasen’s TLC scale, we examined whether separate factors for disordered thought content and disordered thought structure would be produced by the analysis of combined clinical ratings on these two scales.
315 Methods The study used the 18-item BPRS (Overall et al., 1967; Guy et al. 1975; Dingemans et al. 1983) plus additional ratings of elated mood, motor hyperactivity, distractibility, helplessnesshopelessness, sexual preoccupation, and hallucinatory behavior. To these 24 items were added the 18 items from Andreasen’s TLC scale based on rating methods from a manual provided by the author. Two raters, both practiced in the use of the BPRS and TLC scales, independently rated 100 psychiatric patients with a variety of diagnoses. Assigned diagnoses based on DSMII1 criteria (American Psychiatric Association, 1980) were determined by chart review. Each patient was rated only once by each rater. The raters had no knowledge of chart diagnosis, which was determined by a third investigator who did not participate in clinical ratings. The patients included 42 diagnosed as schizophrenic, 11 as manic, 16 as depressive illness, 24 as personality disorder or substance abuse, and 7 with miscellaneous diagnoses. Iterated factor analysis with orthogonal varimax rotation was performed on the BPRS data alone and on the combination of BPRS and TLC data (BMDP, 1979 version). All factors accounting for at least 5% of the total variance in the data were included in the results. BPRS and TLC items with a factor score > 0.60 were considered as loading on the relevant factor and are reported below. This cutoff was selected because it resulted in at least three items loading on each factor and no items loading on more than one factor. Factor coefficients for the relevant items for each factor were used to generate mean factor scores for the population studied. Differences between these factor scores for the three clinical diagnostic groups of schizophrenia, mania, and depression were examined using analysis of variance with subsequent a posteriori comparisons based on Tukey’s w procedure (Sokal and Rohlf, 1969).
Results Factor analysis of the BPRS items, the mania rating items, and the items from Andreasen’s TLC resulted in two separate thought disorder factors. The first of these factors represents disordered thought structure derived largely from TLC items (Table 1) and accounts for the largest proportion of the total variance (24%). The items loading on this factor are the TLC items loss of goal, tangentiality, derailment, circumstantiality, illogicality, pressured speech, and incoherence and the BPRS items disorganized speech and distractibility. The second thought disorder factor loads on hallucinatory statements, hallucinatory behavior, and unusual thought content. This factor appears to measure solely disordered thought content and accounts for only 5% of the total variance. In addition to these two thought disorder factors, the analysis produced a mania factor, plus factors resembling those from previous BPRS factor-analytic studies. The mania factor is composed of two new scale items, elated mood and motor hyperactivity, plus the BPRS item excitement. The fourth, fifth, and sixth factors largely replicate the previously reported BPRS factors of anergia, hostilitysuspiciousness, and anxiety-depression. The fourth factor, termed the negative symptom factor, resembles the previous anergia factor and is composed of ratings for motor retardation, blunted affect, poverty of speech (from the TLC), and disorientation. The fifth factor is composed of ratings for uncooperativeness, hostility, and suspiciousness. The sixth factor is composed of ratings of anxiety, helplessnesshopelessness, and depressive mood. Differences between patients in the diagnostic categories of schizophrenia, mania,
316 and depression for each of the six factors were next examined using analysis of variance and a posteriori testing. Significant differences within these three diagnostic groups were found for the thought content disorder factor (F = 4.37; df 2, 62; p < 0.02) and the mania factor (F= 6.17; df 2,62;p < 0.0 1). A posteriori testing at an alpha of 0.05 demonstrated significant differences between schizophrenic and depressed patients but not between manic patients (means: 5.94 vs. 3.65 vs. 4.54, respectively) and either group. On the mania factor, manic patients differed significantly from both schizophrenic and depressed patients (means: 6.39 vs. 3.81 vs. 4.40, respectively). On the structural thought disorder factor, manic patients rated the highest followed by schizophrenic patients and depressed patients (means: 11.51 vs. 8.32 vs. 7.08, respectively), but these differences did not reach statistical significance. q
q
Table
1. Factor
analysis
of BPRS
and TLC Factor coefficient
Scale item Factor l-Disordered Loss of goal Conceptual
thought
structure
(24% of variance) 0.88
(TLC) disorganization
(BPRSi
0.85
Tangential
(TLC)
0.84
Derailment
(TLC1
0.83
Circumstantial lllogicality
(TLC)
Pressured
speech
Distractibility Incoherent
0.77
(TLC)
0.68
(added)
0.61 0.60
(TLC)
Factor a--Disordered
thought
Hallucinatory
statements
Hallucinatory
behavior
Unusual
thought
Factor 3-Mania Excitement
(BPRSI
0.87
(added)
0.81
(BPRSI
0.62
(6% of variance)
Motor
hyperactivity
0.68 0.68
(added)
Factor 4-Negative
symptoms
retardation
(14% of variance) 0.83
(BPRS)
affect
Poverty
of speech
Disorientation
0.78
(added)
Blunted
0.83
(BPRS)
0.70
(TLC)
(BPRS)
Factor 5-Hostility
0.60
& suspiciousness
Uncooperativeness
(8% of variance)
(BPRS)
0.87 0.88
(BPRS)
Suspiciousness Factor B-Anxiety Anxiety
(5% of variance)
(BPRS)
mood
Hostility
content
content
Elated
Motor
0.65
[TLC)
0.85
( BPRSi & depression
(4% of variance)
i BPRS)
0.78
Helplessness-hopelessness Depressive
mood
[BPRS)
(added)
0.80 0.63
317 Discussion Factor analysis of the BPRS and TLC items produced separate factors for disordered thought structure and disordered thought content in our diagnostically heterogeneous psychiatric population. The factor that accounts for the largest portion of the total variance in the data is derived largely from TLC items, but also contains the BPRS items conceptual disorganization and distractibility. This factor appears to be a very specific measurement of structural thought disorder. Its separation from both the mania factor and the disordered thought content factor argues that disordered thought structure is a separate dimension of psychopathology. Since poverty of speech is the only TLC item to load on any of the other five factors, the TLC seems to have high specificity for the measurement of structural thought disorder. Thus, our results indicate that the recently introduced TLC rating scale is highly specific for the measurement of structural thought disorder and does not measure the same clinical symptom complex as the previously described BPRS thought disorder factor, which nonselectively measures disordered thought structure and content. Either scale may have some advantages depending on the clinical application intended. The addition of six items for rating manic behavior to the 18-item BPRS produces a separate mania factor that contains two of the six new items, plus the BPRS item excitement. This is consistent with the recognition that the authors of the BPRS were trying to reduce clinical factors to a single item. However, the presence of only a single item for rating mania suggests that the original BPRS items may not be optimal for clinical ratings of manic populations. Examination of factor scores generated by the combined BPRS-TLC analysis indicates that two and perhaps three factors are of particular relevance in differentially characterizing schizophrenic, manic, and depressed patients. These three factors rated mania, disordered thought content, and disordered thought structure. As might be expected, manic patients produce the highest scores on the mania factor, with schizophrenic patients producing the lowest scores. Manic patients also show the highest scores on disordered thought structure, while depressed patients show the lowest scores. Schizophrenic patients show the highest scores on hallucinations and delusions (disordered thought content), with depressed patients showing the lowest scores. Curiously, although schizophrenic patients receive the highest rating on the negative symptom or anergia factor, they do not differ significantly from manic and depressed patients on this item; nor do depressed patients differ significantly from the other two groups on the depression-anxiety factor. The present results indicate that the addition of the TLC to the BPRS results in a major improvement in the assessment of disordered thought structure, without altering the other BPRS factors previously reported. The structural thought disorder factor accounted for the largest portion of the variance in a data set based on ratings of patients with a variety of psychiatric diagnoses. For the various groups, manic patients received the highest mean factor scores on this factor, with schizophrenic patients being second highest. Therefore, disordered thought structure, as measured by Andreasen’s TLC, may be more characteristic of manic patients than of schizophrenic patients, who show greater thought content disorder. The conceptual separation of structural thought disorder from thought content disorder seems relevant to the
318 clinical assessment of mixed psychiatric manic and schizophrenic patients. Acknowledgment.
The research
reported
populations,
was supported
particularly
by the Veterans
those containing
Administration
References Psychiatric Association. DSM-III: Diagnostic and Statistical Manual of Mental 3rd ed. APA. Washington, DC (1980). Andreasen, N.J.C. Thought, language, and communication disorders: I. Clinical assessment, definition of terms, and evaluation of their reliability. Archives of General Psychiatry, 36, 13 15 American
Disorders.
(1979a).
Andreasen, N.J.C. Thought. language, and communication disorders: II. Diagnostic significance. Archives of General Psychiatry, 36, 1325 (1979b). Andreasen, N.J.C., and Powers, P.S. Overinclusive thinking in mania and schizophrenia. British Journal
of Psychiatry,
125,452
(1975).
Andreasen, N.J.C., Tsuang, M.T., and Canter, A. The significance of thought disorder in diagnostic evaluations. Comprehensive Psychiatry, 15, 27 (1974). Crow, T.J. Molecular pathology of schizophrenia: More than one disease process? British Journai
of Psychiatry,
Crow, T.J. Positive Journal
of Psychiatry,
137, 66
(1980a).
and negative
schizophrenic
symptoms-The
role of dopamine.
British
137, 383 (1980h).
Dingemans, P.M., Frohn-de Winter, M.L., Bleeker, J.A.C., and Rathod, P. Across-cultural study of the reliability and factorial dimensions of the Brief Psychiatric Rating Scale (BPRS). Psychopharmacology, Guy, W., Cleary,
system.
80, 190 ( 1983).
P., and Bonato, R. R. Methodological implications of a large central data In: Boisser, J.R., Hippius, H., and Pichot, P., eds. Neuropsychopharmacology:
Proceedings of the IX Congress of the Collegium Internationale Neuropsvcho-pharmacologicum, Paris, 7-12 Ju/y, 1974. Excerpta Medica, Amsterdam (1975). Harrow, M., and Quinlan, D. Is thought disorder unique to schizophrenia? Archives General Psychiatry, 34, I.5 (1977).
of
Harrow, M., Silverstein, M., and Marengo, J. Disordered thinking: Does it identify nuclear schizophrenia? Archives of General Psychiatry, 40, 765 (1983). Overall, J.E., and Gorham. D.R. The Brief Psychiatric Rating Scale. Psychological Reports, 10,799 (1962). Overall, J.E., and Klett. C.J. Applied Multivariate Analysis. McGraw-Hill, New York (1972). Overall, J.E., Hollister, L.E., and Pichot, P. Major psychiatric disorders. Archives of General Psychiatry,
16, 146 (1967).
Sokal, R.R., and Rohlf, F.J. Biometry. W.H. Freeman & Co., San Francisco (1969). Silberman, E.K., Weingartner, H., and Post, R. Thinking disorder in depression. Archives General
Psychiatry,
40, 775 (1983).
of