Original Paper
Psychopathology 2010;43:53–62
DOI: 10.1159/000260044
Received: November 18, 2008
Accepted after revision: July 24, 2009
Published online: November 20, 2009
Are There Valid Subtypes of
Schizophrenia? A Grade of Membership
Analysis
Edith Pomarol-Clotet a, b Raymond Salvador a, b Graham Murray c
Subash Tandon d Peter J. McKenna a, b
a
Benito Menni Complex Assistencial en Salut Mental, and b CIBERSAM, Barcelona, Spain; c Department of Psychiatry,
University of Cambridge, Addenbrooke’s Hospital, and d Fulbourn Hospital, Cambridge, UK
Key Words
Schizophrenia subtypes ⴢ Grade of membership analysis
Abstract
Background/Aims: Cluster analysis has had limited success
in establishing whether there are subtypes of schizophrenia.
Grade of membership (GoM) analysis is a multivariate statistical technique which has advantages when, as in schizophrenia, individuals conforming to pure types are uncommon and mixed forms are frequent. Methods: GoM analysis
was applied to 118 chronic schizophrenic patients. The patients were of all clinical subtypes, including 13 with simple
schizophrenia. Both current and ‘lifetime’ symptoms were
assessed, and two different rating systems were used. Results: Specifying 3 pure types resulted in robust findings
across analyses. One pure type corresponded to paranoid
schizophrenia, one to simple schizophrenia and the third
combined elements of hebephrenic and catatonic schizophrenia. Specifying 4 pure types split the original 3 pure
types in ways which were not clinically intuitive. Conclusion:
GoM analysis divides schizophrenia into subtypes along
conventional lines, with the proviso that hebephrenic and
catatonic schizophrenic patients are not separable, at least
in the chronic stage of the illness.
Schizophrenia, it has become a truism to state, is a heterogeneous disorder. The multiplicity of its presentations
and the fact that its outcome can range from full recovery
to profound disability have taxed its credibility as a single
disorder. As a result, there have been many attempts to
define subtypes of schizophrenia which have a more uniform clinical picture and which might show meaningful
differences in prognosis. Historically, a variety of schemes
having been proposed, from Kraepelin’s [1] and Bleuler’s
[2] original 4-way paranoid-hebephrenic-catatonic-simple scheme, through Kraepelin’s [3] later 9-subtype system, to the complex classification of Kleist and Leonhard
[4, 5] which featured 19 different stable end states. However, none of these schemes have been supported particularly well empirically in studies which have used cluster
analysis to generate subgroups of patients [6–9], nor have
the results of these studies agreed with each other.
One reason for the limited success of such studies
could be that cluster analysis generates mutually exclusive subgroups of individuals within a population – subjects can only belong to one cluster and intermediate
forms cannot be accommodated within the model. This
is arguably inappropriate for schizophrenia, where the
reality is a continuously varying spectrum of presentations in which mixed or undifferentiated forms have been
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Dr. Edith Pomarol-Clotet
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considered to be at least as common as classical subtype
presentations. A technique which avoids this difficulty is
grade of membership (GoM) analysis [10–12]. This generates classifications by assigning grades of membership
to empirically generated ‘pure types’, which are intended
to be similar to prototypical or ‘textbook’ cases. Cases
need not be assigned to a single pure type, but can simultaneously and partially express symptoms in 2 or more
classes, with the analysis generating a value for the degree
to which each subject belongs to each pure type. GoM
analysis is considered to be particularly appropriate for
classification in medicine [12], and has been applied psychiatrically to the classification of psychosis [13], depression [14, 15] and other disorders [16, 17]. The present
study used GoM analysis to investigate the subtyping of
clinically stable chronic schizophrenic patients, including some with a well-validated diagnosis of simple schizophrenia.
Method
Patients
The patient sample consisted of 118 in- and out-patients under
the care of a rehabilitation service. The age range was 23–65 years.
All patients were required to have been ill for at least 5 years and
to have reached a state where there had been no major progression
of symptoms in recent years. This was determined by 2 of the authors (P.J.M. and S.T.) who had known most of the patients for
several years. Patients were also required to be persistently symptomatic: this was in order to avoid generation of an asymptomatic pure type as was found in the study of Manton et al. [13].
It was considered important to include patients who were representative of all 4 currently recognized subtypes of schizophrenia. Therefore, the sample included those with paranoid and hebephrenic presentations plus a small number who showed pronounced catatonic symptoms. There were 105 such patients and
they all met Research Diagnostic Criteria for schizophrenia. The
remaining 13 patients did not fulfil existing diagnostic criteria for
schizophrenia because, despite being persistently symptomatic,
they had never shown positive symptoms. These patients met proposed clinical criteria for simple schizophrenia [18] (9 of these
have previously been described in detail [19]).
Procedure
The patients’ current symptoms were rated using the 9th edition of the Present State Examination (PSE) [20] and the schedules
for the assessment of positive and negative symptoms from the
Comprehensive Assessment of Symptoms and History (CASH)
[21]. The PSE is a detailed, semi-structured psychiatric diagnostic
interview, which establishes the presence or absence of many different types of psychotic and neurotic symptoms. Symptoms are
rated as absent, present, or present in severe degree on a 0-1-2
scale. The CASH also assesses a full range of psychotic symptoms,
but unlike the PSE, these are graded along a dimension of severity from 0 to 5.
54
Psychopathology 2010;43:53–62
The patients were examined outside any period of clinical
worsening. Because this could give an incomplete picture of their
symptomatology in some cases – for example, patients who
showed only negative symptoms most of the time but were subject
to flare-ups with positive symptoms from time to time – two PSE
assessments were generated for each patient, one ‘current’ and one
‘lifetime’, the latter combining ratings of current symptoms and
those from any relapses/exacerbations over the last 10 years. For
this, the Syndrome Check List of the PSE was applied to symptoms recorded in the case notes from any previous exacerbations
over the last 10 years.
Data Analyses
PSE data were converted into ‘PSE syndromes’. These consist
of 39 groupings of intuitively rated and/or commonly co-occurring combinations of symptoms (plus a few single-item categories), which form the basis of the diagnostic algorithms used to
generate overall diagnoses. For example, the PSE syndrome, nuclear syndrome includes 8 of the so-called first-rank symptoms of
schizophrenia (thought insertion, thought broadcast, thought
commentary, thought withdrawal, voices discussing patient, delusions of control, delusions of alien penetration, primary delusions); the syndrome hypomania includes 5 items (subjective euphoria, ideomotor pressure, grandiose ideas and actions, hypomanic affect, hypomanic content of speech), and the catatonic
syndrome includes 2 items (mannerisms and posturing, catatonic
movements). There are 3 PSE syndromes related to depression:
simple depression (depressed mood, inefficient thinking, hopelessness, suicidal ideas and plans, and depression on examination), other features of depression (items relating to biological
symptoms) and special features of depression (depressive cognitions such as guilt and self-depreciation). For a PSE syndrome to
be rated as present, the patient typically has to have 2 or more individual symptoms in the category, although the combinatorial
rules vary from syndrome to syndrome.
It was felt necessary to make a few minor alterations to the
composition of the PSE syndromes, as follows:
– In the PSE, third-person auditory hallucinations contribute
only to the nuclear syndrome (first-rank symptoms), and not
to the syndrome auditory hallucinations, which contains only
a single item, ‘voices to patient’. In order to avoid patients who
only experienced third-person auditory hallucinations being
treated as not hallucinated in the GoM analysis, the PSE syndrome auditory hallucinations was modified to include either
second- or third-person auditory hallucinations.
– Poverty of content of speech is 1 of the 3 elements of formal
thought disorder rated in the PSE, but this item does not contribute to the incoherent speech syndrome in the Syndrome
Check List of the PSE. This syndrome was therefore modified
to include this item.
– The item incongruity of affect is not included in any PSE syndrome. As this is a potentially important discriminating variable for hebephrenic schizophrenia, it was included in the
analysis as a syndrome in its own right.
Ratings on individual symptoms formed the basis of the analysis for the CASH. Items under the negative symptom heading
‘attentional impairment’ were excluded from the analysis, as these
are no longer considered negative symptoms but are regarded as
aspects of schizophrenic cognitive impairment. It was only possible to generate a ‘current’ CASH assessment, because the de-
Pomarol-Clotet /Salvador /Murray /
Tandon /McKenna
tailed 0–5 scoring system cannot be applied to information from
case notes.
GoM analysis (DSIGoM, version 10, Decision Systems, Inc.,
1999, www.dsisoft.com) was applied to each of these 3 data sets.
GoM analysis represents the manifest symptoms of cases through
linear combinations of products of 2 types of coefficients [12].
GoM analysis assigns scores or grades of membership (gik), describing the degree to which a given individual i is a member of
the pure type k. GoM scores are non-negative and, for each individual, added over all subtypes sum to 1. Thus it may be that a
case belongs entirely to 1 pure type (gik = 1 for that pure type and
0 for the rest) or partially to several (gik !1 for 2 or more pure
types). Pure types are also described by another parameter, ␭jk,
whose major use is to define the characteristics of the pure type
groups – symptom profiles whose coefficients are estimated to indicate the probability (␭jk) of a symptom j being manifest by a case
belonging entirely (gik = 1) to 1 pure type k. The sum of ␭jk values
over symptoms, for a given pure type, should also add to 1.
GoM analysis also generates a value, H, an information content coefficient. This quantifies how much each item contributes
to the discriminability among the pure types. Small values mean
that as far as the particular variable (i.e. symptom) is concerned,
a random model where there were no pure types would fit just as
well.
For the purposes of the analysis, the PSE syndromes and the
individual CASH symptom scores were considered as the ‘internal questions’, based on which the pure types are determined.
GoM analysis also requires that an external or indicator variable
be used to generate a starting partition for the analysis. This
should tap a known source of variation in the data set. Both age
and score on the Global Assessment of Severity (GAS) [22] were
used in separate analyses for this purpose.
Results
PSE syndrome scores, which are typically scored 0–2
or 0–3 (0 = absent, 1 = minor or partial symptoms, 2 = 1
symptom present, 3 = 2 or more symptoms), were reduced
to present or absent (0 = absent; 1, 2 or 3 = present). Similarly, for the CASH analysis, ‘present’ was defined as a
rating of 2–5 (mild to severe) on individual CASH items,
and absent as 0 or 1 (absent or questionable).
The number of pure types to be used in a GoM analysis can be informed by the clinical question under examination [23]. Alternatively, the number of pure types
above which no further information is gained can be determined mathematically by a likelihood ratio test or by
a similar procedure based on minimizing the Akaike information criterion. In the latter the likelihood is penalized by the amount of estimated parameters [24].
The analyses of both the PSE and CASH data indicated that more than 2 pure types provided the best fit for
the data on the above mathematical grounds. However,
different analyses varied as to whether 3-, 4- or 5-pureAre There Valid Subtypes of
Schizophrenia?
type solutions were optimal, depending on the external
variable used (age or GAS score), and on whether the likelihood ratio or the Akaike information criterion was employed. In terms of intuitiveness, the 3-pure-type solutions were closely similar for both the PSE and CASH
analyses and were also easily interpretable. These are
therefore presented first.
Three-Pure-Type Solutions
The 3-pure-type solution for the PSE current analysis
is shown in table 1. Pure type I was characterized by zero
probabilities on most positive symptoms. The only exceptions were sexual and fantastic delusions and catatonic symptoms which, at 0.15 and 0.11, respectively, were
both well below the threshold of 0.5 for symptoms considered characteristic of a pure type [13]. In contrast,
there were high probabilities on affective flattening, slowness, and a just-below-threshold probability on self-neglect. This type therefore corresponded quite closely to
negative-symptom or simple schizophrenia.
Pure type II resembled paranoid schizophrenia. It
loaded maximally on nuclear symptoms, auditory hallucinations, referential delusions and sexual/fantastic delusions. There were also high probabilities on delusions of
persecution. The probability for incoherent speech was
0.54, just above the cut-off of 0.5. The probability for
grandiose delusions was just below the cut-off of 0.5.
There were maximal probabilities on affective flattening,
but only subthreshold probabilities on slowness, and selfneglect. The probability for residual syndrome (which
consists of hears muttering or whispering, behaves as if
hallucinated and non-social speech) was 0.66. This pure
type, but neither of the other 2, was also associated with
high ratings on depression items and 1 of the 2 anxiety
items.
Pure type III showed maximal probabilities on nuclear syndrome, grandiose and religious delusions and sexual/fantastic delusions. The probability on auditory hallucinations was also high at 0.76. However, the probabilities on delusions of reference and persecution were lower
at 0.55 and 0.58, respectively. This pure type also had a
maximal probability of incoherent speech. The probability for affective flattening was also maximal, as were
those on residual syndrome and self-neglect. Pure type
III was the only pure type to load on catatonic symptoms.
It also was the only pure type to load on incongruity of
affect, but at 0.41 this was slightly below threshold. This
pure type therefore seemed to represent a more severe
form of chronic schizophrenia combining features of
both hebephrenia and catatonia.
Psychopathology 2010;43:53–62
55
Table 1. GoM 3-pure-type solution using PSE ratings
Pure types
I
II
Affective flattening
Slowness
Self-neglect
Worrying
0.88
0.69
0.42
0.31
III
Nuclear syndrome
Simple depression
Affective flattening
Auditory hallucinations
Delusions of reference
Sexual/fantastic delusions
Non-specific psychosis
Special features depression
Tension
Worrying
Social unease
Loss of interest/concentration
Residual syndrome
Delusions of persecution
Irritability
Lack of energy
General anxiety
Incoherent speech
Obsessional neurosis
Grandiose/religious delusions
Slowness
Olfactory hallucinations
Other symptoms depression
Self-neglect
Situational anxiety
1
1
1
1
1
1
1
1
1
1
1
1
0.66
0.61
0.59
0.57
0.55
0.54
0.44
0.42
0.4
0.36
0.34
0.32
0.31
Nuclear syndrome
Incoherent speech
Residual syndrome
Affective flattening
Grandiose/religious delusions
Sexual/fantastic delusions
Non-specific psychosis
Self-neglect
Auditory hallucinations
Delusions of persecutions
Delusions of reference
Catatonic syndrome
Hypomania
Incongruous affect
Irritability
Overactivity
Visual hallucinations
Agitation
1
1
1
1
1
1
1
0.92
0.76
0.58
0.55
0.52
0.45
0.41
0.37
0.35
0.33
0.31
Probabilities of <0.3 are not shown. For this analysis, age was used as the external variable.
Analysis of ‘lifetime’ PSE ratings gave similar results.
In particular, it continued to isolate a pure type which
loaded above threshold only on affective flattening, slowness and self-neglect, together with subthreshold ratings
on non-specific psychosis (0.46) and catatonic syndrome
(0.39). The other 2 pure types showed essentially the same
‘paranoid’ and ‘hebephrenic/catatonic’ patterns of results
as in the analysis of current symptoms.
Analysis Using CASH Ratings
As in the analysis of PSE ratings, 1 pure type (pure
type III) loaded on a wide range of negative symptoms,
although not on blocking and inappropriate affect. There
were no probabilities on any delusion, hallucination or
thought disorder items.
A second pure type (pure type II) was similar to the
paranoid pure type identified by the PSE. It had high
probabilities on delusions, hallucinations and first-rank
symptoms. The probabilities on thought disorder items
56
Psychopathology 2010;43:53–62
were all zero, except for that on poverty of content of
speech, which approached threshold. Apart from affective flattening, which was maximal, suprathreshold probabilities on negative symptoms were scattered and relatively infrequent given the large number of such items in
the CASH.
The remaining pure type (pure type I) loaded most
highly on thought disorder, grandiose delusions and negative symptoms. The probabilities were also high on auditory hallucinations and inappropriate affect. This pure
type had a probability of only 0.29 on catatonic symptoms, but there were no high probabilities on this or any
of the remaining CASH catatonia items (stupor, rigidity,
waxy flexibility and excitement) for any of the other pure
types. The findings are shown in table 2.
Information Content Coefficients
The H values, which quantify each item’s contribution
to discriminability among the pure types, are shown in
Pomarol-Clotet /Salvador /Murray /
Tandon /McKenna
Table 2. GoM 3-pure-type solution using CASH ratings
Pure types
I
II
Grandiose delusions
Derailment
Tangentiality
Incoherence
Illogicality
Paucity of expressive gestures
Affective non-responsivity
Lack of vocal inflections
Grooming and hygiene
Impersistence at work or school
Recreational interest/activities
Unchanging facial expression
Sexual interest/activity
Inappropriate affect
Auditory hallucinations
Increased latency of response
Ideas/delusions of reference
Poor eye contact
Somatic delusions
Pressure of speech
Religious delusions
Decreased spontaneous movements
Delusions of jealousy/other delusions
Poverty of content of speech
Persecutory delusions
Poverty of speech
Delusions mind reading
Somatic hallucinations
1
1
1
1
1
1
1
1
1
1
1
0.91
0.90
0.88
0.77
0.74
0.70
0.70
0.69
0.68
0.65
0.60
0.58
0.50
0.46
0.42
0.40
0.30
III
Persecutory delusions
Religious delusions
Ideas/delusions of reference
Thought insertion
Auditory hallucinations
Affective non-responsivity
Delusions mind reading
Impersistence at work or school
Recreational interest/activities
Delusions of control
Thought withdrawal
Delusions of jealousy/other delusions
Olfactory hallucinations
Lack of vocal inflections
Unchanging facial expression
Paucity of expressive gestures
Grooming and hygiene
Thought broadcasting/echo
Sexual interest/activity
Poverty of content of speech
Grandiose delusions
Visual hallucinations
Somatic hallucinations
1
1
1
1
1
1
0.99
0.96
0.92
0.83
0.81
0.74
0.65
0.63
0.59
0.53
0.52
0.49
0.49
0.43
0.39
0.37
0.36
Unchanging facial expression
Decreased spontaneous movements
Paucity of expressive gestures
Poor eye contact
Affective non-responsivity
Lack of vocal inflections
Poverty of speech
Impersistence at work or school
Recreational interest/activities
Sexual interest/activity
Grooming and hygiene
Increased latency of response
Posturing/mannerisms
1
1
1
1
1
1
1
1
1
1
0.97
0.89
0.35
Probabilities of <0.3 not shown. For this analysis, GAS score was used as the external variable.
table 3. For the PSE analysis, a range of psychotic symptoms including delusions, hallucinations, and to a lesser
extent incoherence of speech, contributed to the final
pure type definition. Also important, however, were depressive symptoms. The CASH rates thought disorder in
considerably more detail than the PSE, and in the CASH
analysis 4 thought disorder items, i.e. derailment, tangentiality, incoherence and illogicality, made a greater
contribution than delusions and hallucinations. In contrast, the values for most of the negative symptoms in the
CASH were low.
Four-Pure-Type Solutions
In the PSE analysis, the 4-pure-type solution retained
the simple and catatonic/hebephrenic pure types essentially unchanged. Paranoid schizophrenia became sepaAre There Valid Subtypes of
Schizophrenia?
rated into 2 pure types which could be construed as ‘florid’ and ‘residual’ forms. The former showed high ratings
on persecutory and referential delusions, nuclear symptoms and auditory hallucinations, whereas in the latter
the suprathreshold probabilities were almost exclusively
on depression, and neurotic symptoms. Both types continued to load maximally on affective flattening.
In the CASH analyses, the 4-pure-type solution essentially preserved the simple, paranoid and hebephrenic
pure types and in addition isolated a type consistent with
mild or residual symptomatology – characterized by the
presence of some delusions and some negative symptoms,
poverty of content of speech, but few other symptoms. In
the 5-pure-type solution, symptomatology typical of paranoid schizophrenia appeared to be represented by 3 pure
types.
Psychopathology 2010;43:53–62
57
Table 3. GoM information content coefficients (H value) in the PSE and CASH analyses
PSE analysis
H value
CASH analysis
H value
Nuclear syndrome
Non-specific psychosis
Simple depression
Spec. features of depression
Social unease
Loss of interest
Auditory hallucinations
Residual syndrome
Incoherent speech
Referential delusions
Grandiose/religious delusions
Sexual/fantastic delusions
Tension
Persecutory delusions
Worrying
General anxiety
Lack of energy
Irritability
Hypomania
Incongruous affect
Catatonic syndrome
Self-neglect
Other depressive symptoms
Obsessional neurosis
Situational anxiety
Visual hallucinations
Olfactory hallucinations
Overactivity
Agitation
Slowness
Hypochondriasis
Depressive del./hall.
Doubtful interview
Affective flattening
Ideas of reference
Hysteria
Depersonalization
Organic impairment
Subcultural del./hall.
0.70
0.70
0.62
0.59
0.59
0.59
0.55
0.52
0.50
0.49
0.49
0.48
0.45
0.26
0.26
0.24
0.24
0.21
0.19
0.17
0.14
0.14
0.13
0.12
0.12
0.10
0.10
0.10
0.09
0.08
0.07
0.05
0.05
0.04
0.03
0.02
0.02
0
0
Derailment
Tangentiality
Incoherence
Illogicality
Thought insertion
Grandiose delusions
Ideas/delusions of reference
Religious delusions
Persecutory delusions
Poor eye contact
Delusions mind reading
Delusions of control
Decreased spontaneous movements
Somatic delusions
Increased latency of response
Pressure of speech
Poverty of speech
Thought withdrawal
Inappropriate affect
Auditory hallucinations
Olfactory hallucinations
Delusions of jealousy, etc.1
Paucity of expressive gestures
Sexual interest/activity
Thought broadcasting/echo
Grooming and hygiene
Lack of vocal inflections
Somatic hallucinations
Visual hallucinations
Unchanging facial expression
Circumstantiality
Delusions of sin or guilt
Posturing/mannerisms
Poverty of content of speech
Blocking
Distractible speech
Excitement
Recreational interest/activities
Clanging
Stupor
Rigidity
Waxy flexibility
Impersistence at work/school
Affective non-responsivity
0.64
0.62
0.61
0.61
0.53
0.51
0.51
0.50
0.45
0.45
0.44
0.38
0.35
0.32
0.32
0.31
0.31
0.30
0.29
0.28
0.27
0.19
0.18
0.16
0.15
0.15
0.14
0.13
0.12
0.12
0.11
0.08
0.08
0.07
0.04
0.03
0.03
0.03
0.02
0.01
0.01
0.01
0.01
0
1
This item was also used to rate miscellaneous other delusions.
Agreement with Clinical Subtype Classification
Without knowledge of the GoM analysis one of the
authors (P.J.M.) assigned each patient to a subtype classification on clinical grounds. Eighty-one patients could
be classified as paranoid (n = 39), hebephrenic (n = 19),
58
Psychopathology 2010;43:53–62
catatonic (n = 10) or simple (n = 13); the remainder were
classified as undifferentiated.
As described above, GoM analysis generates a gik value
for each subject, which indicates the degree to which his
or her symptoms reflect the profile of each pure type. The
Pomarol-Clotet /Salvador /Murray /
Tandon /McKenna
Table 4. Mean gik scores of 81 schizophrenic patients diagnosed
as simple, paranoid or hebephrenic/catatonic clinically
Clinical subtype
GoM mean gik score
I/IIIa
(simple)
II (paranoid)
III/Ia
(hebephrenic/
catatonic)
Analysis using current PSE ratings
Simple
0.62b
Paranoid
0.30
Hebephrenic/catatonic 0.25
0.14
0.48b
0.23
0.09
0.25
0.57b
Analysis using CASH ratings
Simple
0.67b
Paranoid
0.28
Hebephrenic/catatonic 0.26
0.07
0.53b
0.20
0.05
0.25
0.58b
a
Pure types from analyses using current PSE ratings/CASH
ratings, respectively. b Significantly higher gik score in the corresponding clinically identified subtype than in each of the other 2
clinical subtypes (see text).
agreement between each clinical subtype (s = 1, …, S) and
each GoM pure type (k = 1, …, K) was then assessed using the following formula:
 g ik ¬­
­­
 N total ¬­žžž œ
­žž i ‰ s ­­
žžž
­
žŸ N s ®­ž œ g ik ­­
žž
­
Ÿ all i ®­
The second ratio is the cumulative degree of membership to a pure type k for the individuals classified in the
clinical subtype s, divided by the cumulative degree of
membership of all individuals for the same pure type.
The first ratio corrects for the fact that clinical subtypes
are represented by different numbers of individuals in
the sample.
The results are shown in table 4. Although the agreement was far from perfect, it is apparent that in both the
PSE and CASH analyses of current symptomatology,
GoM analysis correctly identified at least twice the proportion of the patients clinically categorized as simple,
paranoid or catatonic/hebephrenic as it incorrectly identified patients in other groups.
Discussion
Attempting to define subgroups of schizophrenia has
always faced problems due to the continuously varying
nature of the disorder’s clinical presentations. Kraepelin
Are There Valid Subtypes of
Schizophrenia?
[3] stated that there were ‘such numerous transitions [between subtypes] that in spite of all efforts it appears impossible at present to delimit them sharply’, and Bleuler
[2] observed that ‘a case which begins as a hebephrenic
may be a paranoid several years later.’ While cluster analytic studies have failed to provide a clear empirical answer to this problem, our study demonstrates that techniques like GoM analysis, which differ from cluster analysis by not specifying mutually exclusive subgroup
membership, can have findings which have much in common with the original paranoid-hebephrenic-catatonicsimple scheme.
When a 3-pure-type GoM solution was specified, a
paranoid-hallucinatory type emerged clearly from both
the PSE and CASH analyses. Formal thought disorder
made only a minor contribution to this pure type and
negative symptoms were also not prominent, taking the
form mainly of affective flattening. This pure type therefore conforms quite closely to the conventional view of
paranoid schizophrenia – a presentation marked mainly
but not exclusively by delusions and hallucinations, occurring against a background of less marked deterioration than in other schizophrenic subtypes.
Both the PSE and CASH analyses also isolated a pure
type characterized only by negative symptoms. Additionally, analysis using ‘lifetime’ assessments suggested that
this pure type was not just isolating patients with current
negative symptoms who had previously had positive
symptoms. This pure type is thus consistent with simple
schizophrenia.
Patients in the third pure type showed high levels of
delusions, particularly grandiose, sexual and fantastic
delusions, plus hallucinations, thought disorder and negative symptoms. This was also the only pure type to load
on inappropriate affect. While this pure type had obvious
affiliations with hebephrenic schizophrenia, it also loaded on catatonic symptoms in the PSE analysis, although
this was only marginally the case in the CASH analysis.
Although some of the analyses on the present set of
data suggested that 4- or 5-pure-type solutions provided
a better mathematical fit than 3, the additional subtypes
they generated were clinically uninformative. The 4pure-type solution in the PSE analysis did not split the
catatonic/hebephrenic pure type, but merely separated
the paranoid pure type into ‘florid’ and ‘residual’ types,
or types dominated more by psychotic and more by neurotic and affective symptoms, respectively. The CASH
analysis preserved the simple, paranoid and hebephrenic
pure types and merely generated a fourth pure type consistent with mild or residual symptomatology.
Psychopathology 2010;43:53–62
59
The fact that formal thought disorder and catatonic
symptoms co-segregated in this study is not entirely
counter-intuitive, as both symptoms have been found to
be prevalent in severely ill, chronically hospitalized patients [25, 26]. Other studies have gone further and implied that hebephrenic and catatonic schizophrenia tend
to merge into one another in the chronic stage of the illness. For example, Winokur and co-workers [27, 28]
found that many patients meeting criteria for hebephrenic schizophrenia tended to develop catatonic symptoms
after several years of illness, and they suggested that hebephrenic/catatonic schizophrenia was a more appropriate term for such cases. Similarly, a study examining the
stability of schizophrenic subtypes over time [29] found
that, while hebephrenic and paranoid schizophrenia
rarely transformed into one another, a proportion of hebephrenic patients were rediagnosed as catatonic at follow-up. In this regard, it is also interesting to note that
Hecker [30], in his original description of hebephrenia,
alluded to the occurrence of catatonic phenomena.
Our finding that GoM analysis isolated a pure type
identifiable as simple schizophrenia could be of some
current interest. Many authors have considered the existence of simple schizophrenia to be questionable [18].
However, two recent studies [19, 31] have made a convincing case that patients showing the typical clinical features
of this presentation continue to be seen. One of the patients in one of these studies [31] has been described in
detail in the DSM-III-R Casebook [32], where the authors
argued that his diagnosis did not fit into any of the categories available in DSM-III-R, and that the diagnostic
concept of simple schizophrenia should be considered as
a possible addition to DSM-IV. However, ‘simple deteriorative disorder’ is currently only included in an appendix
to DSM-IV which contains sets of criteria requiring further study. Clearly, the findings of our study add to the
case for its inclusion in DSM-V.
It is important to note that our findings using GoM
analysis do not merely replicate, using a different technique, the positive, negative and disorganization syndromes found by Liddle [33] and others [34, 35] using
factor analysis. In the first place, GoM analysis isolates
groups of patients not symptoms. Secondly, while the 3pure-type solution produced 1 pure type consisting of patients only with negative symptoms, there were no pure
types corresponding in any meaningful way to patients
with reality distortion or disorganization; both the remaining 2 pure types loaded on a mixture of positive and
negative symptoms.
60
Psychopathology 2010;43:53–62
As argued in the introduction, cluster analysis, which
separates patients into mutually exclusive subgroups,
may be flawed as a method for generating subgroups of
schizophrenic patients. Nevertheless, comparing our results to those of the existing cluster analytic studies of
schizophrenia reveals some commonalities. Carpenter et
al. [6] applied cluster analysis to 600 acute schizophrenic
patients and found that 4 clusters accounted for most of
them. One cluster was characterized by poor insight, persecutory delusions, auditory hallucinations, passivity,
flattened affect and social withdrawal, and so resembled
paranoid schizophrenia. A second cluster shared many of
the characteristics of the first, plus aberrant, agitated or
bizarre behaviour, incoherence of speech, unkempt appearance and flattened and incongruent affect. Carpenter et al. [6] termed this ‘flagrant schizophrenia’, but it
seems equally consistent with hebephrenic schizophrenia. Dollfus et al. [7], Farmer et al. [9] and Lykouras et al.
[8] also isolated one cluster of patients with high scores
on delusions, hallucinations and formal thought disorder
but low scores on negative symptoms, and another where
there were high scores on a wider range of positive and
negative symptoms. These clusters are clearly similar to
the pure types characterized as paranoid and hebephrenic, respectively, in our study. Dollfus et al. [7] and Lykouras et al. [8] also isolated a group of patients with
predominantly negative symptoms. However, as these
authors did not employ a lifetime approach, it would be
dangerous to equate this cluster with simple schizophrenia.
Another relevant technique is latent class analysis.
This is related to cluster analysis, but employs a probabilistic approach and takes into account uncertainties about
class membership. Like GoM analysis, it therefore generates ‘fuzzy’ class membership. However, it should be noted that the most commonly used classification rule in
latent class analysis is modal assignment, which amounts
to assigning each individual to a single class. A number
of studies have applied latent class analysis to schizophrenic patients [36–38] or to groups of unselected psychotic patients [39–41]. However, only one of these studies generated data relevant to subtype classification. From
a population-based sample of 343 patients with broadly
defined schizophrenia or major affective disorder, Kendler et al. [41] identified 4 schizophrenic subgroups, plus 2
affective groups corresponding to major depression and
bipolar disorder with psychotic features, respectively.
Classic schizophrenia was characterized by high scores on
delusions, hallucinations, plus flattening of affect and indices of deterioration; there were also somewhat lower
Pomarol-Clotet /Salvador /Murray /
Tandon /McKenna
probabilities on formal thought disorder and alogia.
Schizophreniform disorder was characterized by high levels of delusions and hallucinations but less prominent
negative symptoms; this subtype also had a better outcome than classic schizophrenia. Schizodepression was
characterized by levels of positive and negative symptoms
which were as high as or higher than for classic schizophrenia, plus prominent depressive symptoms. The final
type, hebephrenia, had a symptom profile which broadly
resembled classic schizophrenia but with higher levels of
formal thought disorder and elevated mood, overactivity,
disinhibited behaviour and pressure of speech.
One study other than ours has used GoM analysis to
examine psychotic patients. Manton et al. [13] applied
GoM analysis to symptom, course, history and outcome
data on 1,065 acute psychotic patients in the International Pilot Study of Schizophrenia [42]. This isolated groups
corresponding closely to mania and depression. The
analysis also yielded 5 pure types ‘related to diagnostic
concepts of schizophrenia and paranoid disorder’. However, these did not divide particularly along conventional
lines. Pure type I loaded uniquely on auditory hallucinations, and non-uniquely on other hallucinations, firstrank symptoms, persecutory delusions and flattening of
affect. Pure type II was characterized uniquely by depersonalization and derealization and symptoms understandable as psychotic elaborations of this. This pure type
also loaded in a non-exclusive way on many other positive
psychotic symptoms. Pure type III loaded almost exclusively on negative symptoms, together with multiple attributes of chronic and residual schizophrenia – autism,
stereotypies, ambivalence and negativism. The 2 remaining schizophrenia-related pure types were similar to each
other and were considered to reflect ‘paranoid psychosis’.
They contained patients with persecutory delusions,
ideas of reference, suspiciousness, irritability, and aggression and bizarre behaviour.
Taken together, studies using cluster analysis, latent
class analysis and GoM analysis appear consistently to
honour the distinction between paranoid and hebephrenic subtypes of schizophrenia. A negative symptom or
simple type has also sometimes been isolated. No study
to date, however, has isolated anything resembling catatonic schizophrenia. There could be several reasons for
this, not least the comparative rarity of this presentation
in acute patients [42, 43]. Assuming enough catatonic patients could be found, it would be interesting to apply
GoM analysis to a sample of acute schizophrenic patients,
where it might be predicted that catatonic and hebephrenic patients would separate more than in the present
study of chronic patients.
Acknowledgements
This study was supported by the Instituto de Salud Carlos III,
Centro de Investigación en Red de Salud Mental, CIBERSAM. We
wish to thank Assen Jablensky for introducing us to Grade of
Membership analysis, and are also grateful to him, Elizabeth
Corder and Milan Dragović for many helpful discussions about
the technique and its application. We are also indebted to Abdullah Kraam and German Berrios for bringing relevant aspects of
Hecker’s work to our attention.
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