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Diagnostic Criteria in Schizophrenia: Accentuate the Positive
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by Anthony S. David and Louis Appleby
At Issue
symptoms of schizophrenia are fundamental to the disorder and should be central to its diagnosis. Much of their recent article is a comparison of the relative value of positive and negative symptoms as diagnostic criteria, which ends with tentative conclusions for the definition of schizophrenia in the DSM-IV. This article presents a criticism of their argument.
tin.—The Editors.
Abstract In a recent article, Andreasen and
Flaum (Schizophrenia Bulletin, Vol. 17, No. 1, 1991) argued that greater emphasis should be placed on negative symptoms in the diagnosis of schizophrenia, leading to a less important role for positive symptoms. This article presents a counter-argument to this view. Positive symptoms are common and reliable and therefore highly useful diagnostically. First-rank symptoms, although not specific to schizophrenia, show good dlscrinvinability. No other type of symptom or investigative method can make such claims to usefulness. Although positive symptoms do not predict outcome, this is not a necessary function of diagnostic criteria. The predictive power of negative symptoms Is, in any case, based largely on studies of patients with chronic disorder. Premorbidly unpaired social development may interact with schizophrenia, worsening the prognosis. We believe positive symptoms have always been the essence of psychiatric disorder and should remain so. Increasing the diagnostic weight given to negative symptoms risks restricting the definition of schizophrenia excessively.
Andreasen and Flaum (1991) have put forward the view that the negative
The Case for the Negative Andreasen and Flaum (1991) believe that too much stress has been placed on positive symptoms in the diagnosis of schizophrenia, although they vary the target of their criticism between first-rank symptoms (FRSs) and positive symptoms in general. Such symptoms, they state, (1) are not present in a sufficient number of cases to be useful; (2) are not specific to schizophrenia; (3) do not predict outcome; (4) are not reliable; and (5) were never meant to be regarded as fundamental to insanity, even by Kraepelin (1904) who called them ". . . merely transitory, and therefore not absolutely diagnostic, features" (p. 26). Negative symptoms, on the other hand, do well on all of these points. Andreasen and Flaum are concerned also by the restrictions of the diagnosis of schizophrenia in DSM-III (American Psychiatric Association 1980) and its revision DSM-III-R (American Psychiatric Association 1987), in particular its duration criterion by which symptoms of schizophrenia must have been present for at least 6 months and by the reliance on positive phenomena at the expense of Reprint requests should be tent to Dr. A.S. David, Dept. of Psychological Medicine, King's College Hospital, Bessemer Rd., London, SES 9RS, United Kingdom.
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The At Issue section of the Schizophrenia Bulletin contains viewpoints and arguments on controversial issues. Articles published in this section may not meet the strict editorial and scientific standards that are applied to major articles in the Bulletin. In addition, the viewpoints expressed in the following article do not necessarily represent those of the staff or the Editorial Advisory Board of the Bulle-
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• DSM-III and ICD-10 are different, but could be less so if DSM-III adopted ICD-lCs 1-month duration criterion. The whole ICD-10 definition could not be adopted because it emphasizes first-rank symptoms. • DSM-III should be altered to take account of future discriminant function analyses of symptoms found in different conditions, possibly leading to separate criteria for first-episode patients. • Negative symptoms, as the most fundamental features of schizophrenia, should be given more prominence in the diagnostic systems, meaning that "other types of criteria could be written that would increase the emphasis on negative symptoms" (Andreasen and Flaum 1991, p. 44). There are three ways of doing this: (1) creating two lists of required symptoms, one composed of negative symptoms; (2) rewriting the "deterioration in function" criterion of DSM to be specifically "couched in terms of negative symptoms"; and (3) dividing prodromal symptoms into positive and negative, thus stressing the prodromal and residual states in which negative symptoms can be found. • Options available with regard to DSM-III criteria include the following: (1) leave the existing definition the same, (2) bring the duration criterion in line with ICD-10, (3) broaden the clinical criteria to include negative symptoms.
The Case for the Positive Are Andreasen and Flaum right7 Is the diagnostic weight attached to the positive symptoms of schizophrenia unjustifiable? It is worth examining each of the above criticisms individually. Positive Symptoms Are Not Sufficiently Common To Be Useful. Much of this criticism is directed not at positive symptoms in general but at FRSs. Four studies are quoted in which the frequency of FRSs was recorded from a sample of patients with schizophrenia (Mellor 1970; Carpenter et al. 1973; Carpenter and Strauss 1974; Koehler et al. 1977). Most individual symptoms occurred at a frequency between 10 and 30 percent, and in only one study did any FRS (delusional perception) occur in more than 50 percent of cases (Koehler et al. 1977). The conclusion reached by Andreasen and Flaum (1991, p. 35) is that "base rates (of FRSs) are relatively low" or at least not common enough to be the basis of the diagnostic criteria for schizophrenia and, by implication, that the same is true of positive symptoms as a whole. The point reappears in the final conclusions as a reason for not adopting the ICD-10 criteria in toto. However, each of these studies also quoted the frequency of cases in which at least one FRS was present. In three, the figure was over 50 percent and in one it was 72 percent (Mellor 1970). In the other, a frequency of 33 percent was found (Koehler et al. 1977), but in this study the method used was case note review while the others employed a prospective design. In other words, each FRS was present in a minority of cases but, taken together, they were found in at least half of the patients examined. They are therefore more diagnostically useful than Andreasen and Flaum suggest.
There is a second counter-argument on the required frequency of a diagnostic feature. A clinical sign can be diagnostically useful even though it is uncommon—in Wilson's disease, for example, the Kayser-Fleischer ring is often invisible to the naked eye, but when it is visible, it is diagnostic. The same is true of less "pathognomonic" signs such as the flapping tremor of hepatic encephalopathy or the confabulation of Korsakov's psychosis. Similarly, individual FRSs, although often absent, are indicative of schizophrenia and should be included in any list of clinical criteria. Diagnostic usefulness is therefore a balance between frequency and specificity and, taken collectively, the FRSs are reasonably frequent and reasonably specific. A good classification system places such symptoms alongside other important clinical features to allow them to influence diagnosis strongly when they are present but not prevent diagnosis when they are absent. For this reason ICD-10 encourages the diagnosis of schizophrenia in the presence of any FRS, but the diagnosis can still be made in their absence, if persistent delusions are evident or in the presence of any two of the following: persistent hallucinations, formal thought disorder, catatonia, or negative symptoms. DSM-III presents a similar list of positive symptoms but also insists on deterioration in social functioning and therefore emphasizes negative symptoms indirectly. When Andreasen and Flaum apply their argument on frequency to positive symptoms as a whole it becomes weaker still, because, according to their own figures, delusions and hallucinations show frequencies of 86 percent and 66 percent, respectively. This should not be surprising because these are the phenomena that lead clinicians to diagnose schizophrenia. Are the
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negative features. Because of these restrictions, schizophrenia in DSM-III and DSM-111-R is defined more narrowly than in ICD-10 (World Health Organization 1989) so that the two systems, though compatible, are not the same. These points lead Andreasen and Flaum to four not entirely distinct conclusions:
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Positive Symptoms Are Not Specific to Schizophrenia. Again this argument is put forward about FRSs rather than positive symptoms generally. Clearly neither is unique to schizophrenia but equally clearly neither is used in this way. According to ICD-10, schizophrenia can be diagnosed in patients with FRSs, as long as prominent affective disturbance, overt brain disease, and drug intoxication or withdrawal are not present. In DSM-III, the diagnosis can only be made if the duration and deterioration criteria are satisfied. As in most medical classifications, additional diagnostic criteria are used to compensate for the lack of specificity of any one. The presence of FRSs in patients with affective disorder, especially mania, is an important challenge to their specificity for schizophrenia because Schneider has said that when an FRS is present, it ". . . must have undisputed precedence when it comes to the allocation of the individual case" (Schneider 1959, p. 135). However, this need not be taken literally. Wing and colleagues (1974), who must be credited with disseminating Schneider's writings to English-speaking psychiatrists internationally, stated that "the term pathognomonic, if interpreted to mean 100 percent accuracy, cannot at the present time be used of any symptom known to medicine. It is certainly not applicable to psychiatry" (Wing and Nixon 1975, p. 858). Wing and Nixon take pains to avoid such absolute claims for their criteria, as there exists no gold standard against which they may be measured—hence their preference for the term "discrepancy"
rather than "error" or "misdassification." For most diagnosticians, a rate of 8 percent to 23 percent for FRSs in mania seems quite acceptable, given the imperfect reliability coefficients. Similarly, in the largest international sample in which this was studied, the International Pilot Study for Schizophrenia (IPSS; Wing et al. 1974), 13 out of 79 (16.5%) of the manic sample and 10 out of 229 (4.4%) of the depressives, had some element of the schizophrenic "nuclear syndrome." These percentages may be inflated by the use of differing thresholds to mark the presence of a symptom, and detailed analysis of such cases often revealed ambiguous instances of FRSs (Wing and Nixon 1975). However, it should be added that the authors were more concerned with specificity than sensitivity in this instance. We do not know how many schizophrenic patients scored positively with dubious FRSs. In Taylor and Abrams' first study (1973), which examined 52 patients who met research criteria for mania yet had a clinical diagnosis of schizophrenia or nonaffective psychosis, the presence of FRS was 11.5 percent. The published case vignettes do not contain any convincing instance of an FRS, and, furthermore, the response to lithium in six of the eight cases would not now be taken as distinguishing categorically between the functional psychoses (Johnstone et al. 1988). In the later Taylor and Abrams' study (1975), the figure was 7.5 percent (4 out of 53 cases); the duration and severity of these symptoms was not reported. This is important because a wide definition greatly increases the likelihood of discrepant diagnoses. CGrady (1990) found that 73 percent of new admissions with Research Diagnostic Criteria (RDC; Spitzer et al. 1978) schizophrenia had FRSs compared with 14 percent of
affective disorder patients. However, using a narrow definition of FRSs, the proportions were 73 percent and 6 percent, respectively. The index most commonly used to determine the diagnostic usefulness of a symptom is discriminability, a measure of the proportion of cases with the symptom who have the appropriate diagnosis. From the IPSS, the figures for FRSs are between 0.95 and 0.97 in schizophrenia compared with 0.02 and 0.03 in mania (Wing et al. 1974). Are the negative symptoms any more spedfic7 It seems unlikely considering the large number of functional and neuropsychiatric disorders in which psychosocial impairment occurs (Sommers 1985; Carpenter 1991). Chronic depression, substance abuse, personality disorders, epilepsy, and so on, all affect attentiveness, volition, and sociability. Empirical data on this are lacking because few studies have determined base rates for negative symptoms in heterogeneous patient groups. One such study found a higher prevalence of negative symptoms in depression than in schizophrenia (Kulhara and Chadda 1987). Andreasen and Flaum's article does not clarify this. The reference to Andreasen (1989) given in table 6 does not appear in the reference list and most of the studies in table 7 are either unpublished or not available in English. The one exception (Moscarelli et al. 1987) seems promising in that of a sample of 96 subjects, 59 (61%) were diagnosed as having schizophrenia. Unfortunately, much of the reliability data quoted are based on only 24 schizophrenic patients. The results in table 8 (presumably based on Andreasen 1985), plus those in the larger of the samples in table 9, are based on '111 consecutively admitted schizophrenic patients, most of whom had established chronicity . . . "
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negative features any more frequent 7 The Iowa results suggest not, the one exception being blunted affect (87%), which is already included in both ICD-10 and DSM-1U.
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Positive Symptoms Do Not Predict Outcome. Negative Symptoms Do. Andreasen and Flaum make two references to predictive validity. First, they comment on the poor prediction of outcome reported for the main current diagnostic criteria (Helzer et al. 1981, 1983; Endicott et al. 1986). In listing the virtues of negative symptoms, they include the prediction of poor outcome (Carpenter et al. 1978; Johnstone et al. 1979; Pogue-Geile and Harrow 1984, 1985). We see several possible misconceptions in what they imply. To start with, the diagnosis of schizophrenia, regardless of the details of diagnostic criteria, must surely reduce a person's overall functioning in comparison to the general population, otherwise its definition as a disease would be in doubt. Second, they confuse diagnosis with prognosis. It is not necessary for
diagnostic criteria to be prognostic indicators; these are separate, unless the outcome of a disorder is fairly uniform, which is far from true of schizophrenia. Third, any criterion that restricts diagnosis will improve predictive validity by creating a more uniform syndrome. Hence the 6-month criterion of DSM-III must improve prediction but only by a self-fulfilling maneuver, that is, by removing short duration illnesses from any patient sample. An allied source of confusion is between severity and prognosis. An illness that is more severe should have a worse prognosis and vice versa. Negative symptom patients have more cognitive impairment (Owens and Johnstone 1980), motor disorders, and tardive dyskinesia (Waddington et al. 1987). Moreover, any biological trait markers will be expected to be more prominent in more severe cases. Although the evidence is not unanimous, almost all biological markers seem to predominate in patients with negative symptoms. Such studies are reviewed in Andreasen (1990) and quoted with approval by Andreasen and Flaum in their article. To these could be added magnetic resonance imaging (MRI) studies of cerebral abnormalities (Williamson et al. 1991), information processing speed (Weiner et al. 1990), event-related potentials (Pfefferbaum et al. 1989), and visual-evoked potentials (Schwarzkopf et al. 1990), plus cerebral blood flow studies showing hypofrontality, which is invariably used to explain negative symptoms (e.g., Weinberger and Berman 1988). Because the bulk of studies all point in the same direction (rather than some markers consistently going along with positive symptoms), we take this as support for the severity explanation rather than as a validation for the concept of two schizophrenic syndromes, positive and negative. A pro-
spective study of patients with homogeneous negative symptoms, some of whom had, say, large ventricles, or alternatively, a cohort of mixed schizophrenic subjects selected on the basis of large ventricles would be necessary to determine whether either of these factors exerted independent effects on outcome. Another possibility is that positive and negative syndromes, while independent, may occur together. This situation is common (DeLeon et al. 1989) and of practical importance, but theoretically it is the least interesting. Assodations such as this do not allow strong inferences in psychology (Shallice 1988; David, in press), whereas dissociations, positive without negative symptoms and vice versa, prove that the two-symptom dusters cannot share a single pathological mechanism. Fourth, the nature of negative symptoms indudes, by definition, aspects of poor prognosis. Anergia, impersistence at work, avolitionapathy, and work inattentiveness are descriptions of patients who are currently not doing well in psychosodal rehabilitation, so their predictive power is spurious. A related problem arises out of Strauss and Carpenter's important finding (Strauss and Carpenter 1974) that premorbid adjustment is one of the strongest predictors of outcome—that is, some negative symptoms such as those above may not be symptoms at all but baseline levels of functioning. It may be the combination of these with schizophrenia that is so deleterious (see also Dworkin et al. 1990). In a recently published factor analytic study (Lenzenweger et al. 1991), schizophrenic phenomenology was best accounted for by a 3-factor model in which premorbid poor social adjustment is the third factor, quite independent of both positive and negative symptoms.
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(p. 41) so it is not surprising that this group had prominent negative symptoms (as well as delusions and hallucinations). Andreasen and Flaum obviously support the "radical change" introduced by the DSM, from viewing negative symptoms as a useful basis of subdassification to seeing them as central to the diagnosis. However, in 1982 Andreasen and Olsen wrote regarding the Scale for the Assessment of Negative Symptoms (SANS; Andreasen 1984): "Because these are criteria for subtyping schizophrenia, all patients must first meet DSM-III criteria for schizophrenia" (p. 790). This article went on to report reliability and validity data from 52 schizophrenic patients who had a mean of five admissions to hospitals with durations of over 12 months and histories averaging 8 years. Clearly the group was biased toward chronidty and was unlikely to include patients with uncertain diagnoses.
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Positive Symptoms Are Not Reliable. Andreasen and Flaum (1991) state: The literature currently supporting their [negative symptoms'] stability and validity is much stronger than the literature that can be marshaled in support of first-rank symptoms or probably even positive symptoms in general. Most existing evidence indicates that positive symptoms are neither internally consistent nor stable over time. (pp. 37-38] Several studies have examined the interrater reliability of symptoms in schizophrenia, and these are quoted in detail by the authors. The tables make it dear that, although good reliability has at times been demonstrated for negative symptoms also, the best reliability has been reported for positive phenomena, including those of first rank. Positive Symptoms Are Not Fundamental to Schizophrenia. With the advent of imaging technology and molecular genetics it is tempting to view phenomenology as irrelevant. However, no biological technique has come near the sensitivity and specificity of delusions and hallucinations for schizophrenia. For example, computed tomographic (CT) scanning, the most widely studied biological tool in this field, while showing group differences between schizophrenic and other psychiatric patients, also shows a large overlap between groups. Indeed, lateral ventricular enlargement
has been calculated as occurring in somewhere between 7 to 94 percent of schizophrenic patients (Smith and Iacono 1986). When medical controls are used for comparison, schizophrenic patients' ventricular brain ratios (VBRs) may be completely within the range of the controls. The sensitivity and specificity of CT scanning is therefore extremely low. While negative symptoms—in the Jacksonian scheme favored by Andreasen and Flaum—are understandable as a loss of normal functioning, positive symptoms, particularly FRSs, do not obviously reflect a normal function that has been disinhibited by disease. FRSs are outside normal experience—although apparently nonpsychotic people have reported hearing voices referring to them (usually by name) or hearing their thoughts echoed (Chapman and Chapman 1980; Posey and Losch 1983-84), this is rare and may be an artifact of the demand characteristics of certain questionnaires and interviews. When scrutinized, the reported experiences would not be classed as FRSs according to the Present State Examination (Wing et al. 1974). Jaspers emphasized the ununderstandability of these symptoms, which distinguished them from, for example, apathy and avolition. He wrote: The most profound distinction in psychic life seems to be that between what is meaningful and allows empathy and what in its particular way is ununderstandable, mad in the literal sense, schizophrenic psychic life. . . . Pathological psychic life of the first kind we can comprehend vividly enough as an exaggeration or diminution of known phenomena. . . . Pathological psychic life of the second kind we cannot adequately comprehend in this way. [Jaspers 1913/1963, pp. 577-578]
He continued: For lay persons madness means senseless raving, affectless confusion, delusion, incongruous affects, a crazy personality. . . . Holding these views the lay person has hit upon a basic difference within morbid psychic life which even today we cannot formulate clearly and precisely but which remains one of the most interesting problems. [Jaspers 1913/1963, pp. 577-578] Positive symptoms, especially FRSs, imply a breach in the sense of self and the integrity of thought. This, after all, is what most clearly marks schizophrenia as a pathological entity.
Conclusion Should DSM-IV be modified to give negative symptoms more prominence, to make the diagnosis of schizophrenia more likely when they are present and less likely when they are absent? The justification provided by Andreasen and Flaum is flawed in several places and the effect of such a change—a further restriction on DSM-III schizophrenia—is something they themselves wish to avoid. In their initial summary they go against the thrust of the text of their article by advocating prominence for both the positive and the negative. But this already exists. In both ICD-10 and DSM-III-R, blunting is specifically listed under the clinical criteria while in DSM-III-R social deterioration is a requirement. Certainly the negative symptoms need further investigation—their psychology, etiology and treatment—but their place in classification is already satisfactory. They add to the diagnosis of schizophrenia but do not detract from the importance of delusions and hallucinations, which, we contend, remain the essence of schizophrenia.
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Finally, the authors quote the study by Endicott and colleagues (1986) as confirming the poor predictive power of all the diagnostic systems they examined. They fail to mention that this study concluded that a composite of elements of DSM-1I1 and at least one FRS achieved the best predictive power, at least in the short term.
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Kraepelin, E. Lectures on Clinical Psychiatry. Translated and edited by Thomas Johnstone. New York: Hafner, 1904. Kulhara, P., and Chadda, R. Study of negative symptoms in schizophrenia and depression. Comprehensive Psychiatry, 28:229-235,1987. Lenzenweger, M.F.; Dworkin, R.H.; and Wethington, E. Examining the underlying structure of schizophrenic phenomenology: Evidence for a threeprocess model. Schizophrenia Bulletin, 17:515-524, 1991. Mellor, C S . First-rank symptoms of schizophrenia. British Journal of Psychiatry, 117:15-23, 1970. Moscarelli, M.; Maffei, C ; and Cesana, B.M. An international perspective on assessment of negative and positive symptoms in schizophrenia. American Journal of Psychiatry, 144:1595-1598, 1987. Owens, D . G . C , and Johnstone, E.C. The disabilities of chronic schizophrenia—Their nature and the factors contributing to their development.
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Pfefferbaum, A.; Ford, J.M.; White, P.M.; and Roth, W.T. P3 in schizophrenia is affected by stimulus modality, response requirements, medication status and negative symptoms. Archives of General Psychiatry, 46:1035-1044, 1989. Pogue-Geile, M.F., and Harrow, M. Negative and positive symptoms in schizophrenia and depression: A followup. Schizophrenia Bulletin, 10:371-387, 1984. Pogue-Geile, M.F., and Harrow, M. Negative symptoms in schizophrenia: Their longitudinal course and prognostic importance. Schizophrenia Bulletin, 11:427-439, 1985. Posey, T.B., and Losch, M.E. Auditory hallucinations of hearing voices in 375 normal subjects. Imagination, Cognition and Personality, 3:99-113, 1983-84. Schneider, K. Clinical Psychopathology. Translated by M.W. Hamilton, New York: Grune & Stratton, 1959. Schwarzkopf, S.B.; Lamberti, J.S.; Jiminez, M.; Kane, C.F.; Henricks, M.; and Nasrallah, H.A. Visual evoked potential correlates of positive/negative symptoms in schizophrenia. Biological Psychiatry, 27:400-410, 1990.
Smith, G.N., and Iacono, W.G. Lateral ventricular size in schizophrenia and choice of control group. [Letter to the Editor] Lancet, 1:1450, 1986. Sommers, A.A. Negative symptoms: Conceptual and methodological problems. Schizophrenia Bulletin, 11:364379,1985. Spitzer, R.L.; Endicott, J.; and Robins, E. Research Diagnostic Criteria: Rationale and reliability. Archives of General Psychiatry, 35:773-782, 1978. Strauss, J.S., and Carpenter, W.T., Jr. The prediction of outcome in schizophrenia. Archives of General Psychiatry, 31:37-42, 1974. Taylor, M.A., and Abrams, R. The phenomenology of mania: A new look at some old patients. Archives of General Psychiatry, 29:520-522, 1973. Taylor, M.A., and Abrams, R. Acute mania: Clinical and genetic study of responders and non-responders to treatment. Archives of General Psychiatry, 32:863-865,1975. Waddington, J.C; Youssef, H.A.; Dolphin, C ; and Kinsella A. Cognitive dysfunction, negative symptoms and tardive dyskinesia in schizophrenia. Archives of General Psychiatry, 44:907-912, 1987. Weinberger, D.R., and Berman, K.F. Speculation on the meaning of cerebral metabolic hypofrontality. Schizophrenia Bulletin, 14:157-168, 1988. Weiner, R.U.; Opler, L.A.; Kay, S.R.; Merriam, A.E.; and Papouchis, N.
Visual information processing in positive, mixed and negative schizophrenic syndromes. Journal of Nervous and Mental Disease, 178:616626,1990. Williamson, P.; Pelz, D.; Merskey, H.; Morrison, S.; and Conlon, P. Correlation of negative symptoms in schizophrenia with frontal lobe parameters on magnetic resonance imaging. British Journal of Psychiatry, 159:130-134, 1991. Wing, J.K.; Cooper, J.E.; and Sartorius, N. The Measurement and Classification of Psychiatric Symptoms. London: Cambridge University Press, 1974. Wing, J.K., and Nixon, J. Discriminating symptoms in schizophrenia. Archives of General Psychiatry, 32:853-859, 1975. World Health Organization. "Mental Disorders: Glossary and Guide to Their Classification in Accordance With the Tenth Revision of the International Classification of Disease. Draft of Chapter 5: Mental, Behavioral and Developmental Disorders." Geneva, Switzerland, 1989.
The Authors Anthony S. David, MRCP, MRCPsych, is a Senior Lecturer, Department of Psychological Medicine, King's College Hospital, London, United Kingdom. Louis Appleby, MRCP, MRCPsych, is a Senior Lecturer, University Department of Psychiatry, Withington Hospital, Manchester, United Kingdom.
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Shallice, T. From Neuropsychology to Mental Structure. Cambridge: Cambridge University Press, 1988.
Diagnostic Criteria in Schizophrenia: Accentuate the Positive
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by Anthony S. David and Louis Appleby
At Issue
symptoms of schizophrenia are fundamental to the disorder and should be central to its diagnosis. Much of their recent article is a comparison of the relative value of positive and negative symptoms as diagnostic criteria, which ends with tentative conclusions for the definition of schizophrenia in the DSM-IV. This article presents a criticism of their argument.
tin.—The Editors.
Abstract In a recent article, Andreasen and
Flaum (Schizophrenia Bulletin, Vol. 17, No. 1, 1991) argued that greater emphasis should be placed on negative symptoms in the diagnosis of schizophrenia, leading to a less important role for positive symptoms. This article presents a counter-argument to this view. Positive symptoms are common and reliable and therefore highly useful diagnostically. First-rank symptoms, although not specific to schizophrenia, show good dlscrinvinability. No other type of symptom or investigative method can make such claims to usefulness. Although positive symptoms do not predict outcome, this is not a necessary function of diagnostic criteria. The predictive power of negative symptoms Is, in any case, based largely on studies of patients with chronic disorder. Premorbidly unpaired social development may interact with schizophrenia, worsening the prognosis. We believe positive symptoms have always been the essence of psychiatric disorder and should remain so. Increasing the diagnostic weight given to negative symptoms risks restricting the definition of schizophrenia excessively.
Andreasen and Flaum (1991) have put forward the view that the negative
The Case for the Negative Andreasen and Flaum (1991) believe that too much stress has been placed on positive symptoms in the diagnosis of schizophrenia, although they vary the target of their criticism between first-rank symptoms (FRSs) and positive symptoms in general. Such symptoms, they state, (1) are not present in a sufficient number of cases to be useful; (2) are not specific to schizophrenia; (3) do not predict outcome; (4) are not reliable; and (5) were never meant to be regarded as fundamental to insanity, even by Kraepelin (1904) who called them ". . . merely transitory, and therefore not absolutely diagnostic, features" (p. 26). Negative symptoms, on the other hand, do well on all of these points. Andreasen and Flaum are concerned also by the restrictions of the diagnosis of schizophrenia in DSM-III (American Psychiatric Association 1980) and its revision DSM-III-R (American Psychiatric Association 1987), in particular its duration criterion by which symptoms of schizophrenia must have been present for at least 6 months and by the reliance on positive phenomena at the expense of Reprint requests should be tent to Dr. A.S. David, Dept. of Psychological Medicine, King's College Hospital, Bessemer Rd., London, SES 9RS, United Kingdom.
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The At Issue section of the Schizophrenia Bulletin contains viewpoints and arguments on controversial issues. Articles published in this section may not meet the strict editorial and scientific standards that are applied to major articles in the Bulletin. In addition, the viewpoints expressed in the following article do not necessarily represent those of the staff or the Editorial Advisory Board of the Bulle-
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• DSM-III and ICD-10 are different, but could be less so if DSM-III adopted ICD-lCs 1-month duration criterion. The whole ICD-10 definition could not be adopted because it emphasizes first-rank symptoms. • DSM-III should be altered to take account of future discriminant function analyses of symptoms found in different conditions, possibly leading to separate criteria for first-episode patients. • Negative symptoms, as the most fundamental features of schizophrenia, should be given more prominence in the diagnostic systems, meaning that "other types of criteria could be written that would increase the emphasis on negative symptoms" (Andreasen and Flaum 1991, p. 44). There are three ways of doing this: (1) creating two lists of required symptoms, one composed of negative symptoms; (2) rewriting the "deterioration in function" criterion of DSM to be specifically "couched in terms of negative symptoms"; and (3) dividing prodromal symptoms into positive and negative, thus stressing the prodromal and residual states in which negative symptoms can be found. • Options available with regard to DSM-III criteria include the following: (1) leave the existing definition the same, (2) bring the duration criterion in line with ICD-10, (3) broaden the clinical criteria to include negative symptoms.
The Case for the Positive Are Andreasen and Flaum right7 Is the diagnostic weight attached to the positive symptoms of schizophrenia unjustifiable? It is worth examining each of the above criticisms individually. Positive Symptoms Are Not Sufficiently Common To Be Useful. Much of this criticism is directed not at positive symptoms in general but at FRSs. Four studies are quoted in which the frequency of FRSs was recorded from a sample of patients with schizophrenia (Mellor 1970; Carpenter et al. 1973; Carpenter and Strauss 1974; Koehler et al. 1977). Most individual symptoms occurred at a frequency between 10 and 30 percent, and in only one study did any FRS (delusional perception) occur in more than 50 percent of cases (Koehler et al. 1977). The conclusion reached by Andreasen and Flaum (1991, p. 35) is that "base rates (of FRSs) are relatively low" or at least not common enough to be the basis of the diagnostic criteria for schizophrenia and, by implication, that the same is true of positive symptoms as a whole. The point reappears in the final conclusions as a reason for not adopting the ICD-10 criteria in toto. However, each of these studies also quoted the frequency of cases in which at least one FRS was present. In three, the figure was over 50 percent and in one it was 72 percent (Mellor 1970). In the other, a frequency of 33 percent was found (Koehler et al. 1977), but in this study the method used was case note review while the others employed a prospective design. In other words, each FRS was present in a minority of cases but, taken together, they were found in at least half of the patients examined. They are therefore more diagnostically useful than Andreasen and Flaum suggest.
There is a second counter-argument on the required frequency of a diagnostic feature. A clinical sign can be diagnostically useful even though it is uncommon—in Wilson's disease, for example, the Kayser-Fleischer ring is often invisible to the naked eye, but when it is visible, it is diagnostic. The same is true of less "pathognomonic" signs such as the flapping tremor of hepatic encephalopathy or the confabulation of Korsakov's psychosis. Similarly, individual FRSs, although often absent, are indicative of schizophrenia and should be included in any list of clinical criteria. Diagnostic usefulness is therefore a balance between frequency and specificity and, taken collectively, the FRSs are reasonably frequent and reasonably specific. A good classification system places such symptoms alongside other important clinical features to allow them to influence diagnosis strongly when they are present but not prevent diagnosis when they are absent. For this reason ICD-10 encourages the diagnosis of schizophrenia in the presence of any FRS, but the diagnosis can still be made in their absence, if persistent delusions are evident or in the presence of any two of the following: persistent hallucinations, formal thought disorder, catatonia, or negative symptoms. DSM-III presents a similar list of positive symptoms but also insists on deterioration in social functioning and therefore emphasizes negative symptoms indirectly. When Andreasen and Flaum apply their argument on frequency to positive symptoms as a whole it becomes weaker still, because, according to their own figures, delusions and hallucinations show frequencies of 86 percent and 66 percent, respectively. This should not be surprising because these are the phenomena that lead clinicians to diagnose schizophrenia. Are the
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negative features. Because of these restrictions, schizophrenia in DSM-III and DSM-111-R is defined more narrowly than in ICD-10 (World Health Organization 1989) so that the two systems, though compatible, are not the same. These points lead Andreasen and Flaum to four not entirely distinct conclusions:
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Positive Symptoms Are Not Specific to Schizophrenia. Again this argument is put forward about FRSs rather than positive symptoms generally. Clearly neither is unique to schizophrenia but equally clearly neither is used in this way. According to ICD-10, schizophrenia can be diagnosed in patients with FRSs, as long as prominent affective disturbance, overt brain disease, and drug intoxication or withdrawal are not present. In DSM-III, the diagnosis can only be made if the duration and deterioration criteria are satisfied. As in most medical classifications, additional diagnostic criteria are used to compensate for the lack of specificity of any one. The presence of FRSs in patients with affective disorder, especially mania, is an important challenge to their specificity for schizophrenia because Schneider has said that when an FRS is present, it ". . . must have undisputed precedence when it comes to the allocation of the individual case" (Schneider 1959, p. 135). However, this need not be taken literally. Wing and colleagues (1974), who must be credited with disseminating Schneider's writings to English-speaking psychiatrists internationally, stated that "the term pathognomonic, if interpreted to mean 100 percent accuracy, cannot at the present time be used of any symptom known to medicine. It is certainly not applicable to psychiatry" (Wing and Nixon 1975, p. 858). Wing and Nixon take pains to avoid such absolute claims for their criteria, as there exists no gold standard against which they may be measured—hence their preference for the term "discrepancy"
rather than "error" or "misdassification." For most diagnosticians, a rate of 8 percent to 23 percent for FRSs in mania seems quite acceptable, given the imperfect reliability coefficients. Similarly, in the largest international sample in which this was studied, the International Pilot Study for Schizophrenia (IPSS; Wing et al. 1974), 13 out of 79 (16.5%) of the manic sample and 10 out of 229 (4.4%) of the depressives, had some element of the schizophrenic "nuclear syndrome." These percentages may be inflated by the use of differing thresholds to mark the presence of a symptom, and detailed analysis of such cases often revealed ambiguous instances of FRSs (Wing and Nixon 1975). However, it should be added that the authors were more concerned with specificity than sensitivity in this instance. We do not know how many schizophrenic patients scored positively with dubious FRSs. In Taylor and Abrams' first study (1973), which examined 52 patients who met research criteria for mania yet had a clinical diagnosis of schizophrenia or nonaffective psychosis, the presence of FRS was 11.5 percent. The published case vignettes do not contain any convincing instance of an FRS, and, furthermore, the response to lithium in six of the eight cases would not now be taken as distinguishing categorically between the functional psychoses (Johnstone et al. 1988). In the later Taylor and Abrams' study (1975), the figure was 7.5 percent (4 out of 53 cases); the duration and severity of these symptoms was not reported. This is important because a wide definition greatly increases the likelihood of discrepant diagnoses. CGrady (1990) found that 73 percent of new admissions with Research Diagnostic Criteria (RDC; Spitzer et al. 1978) schizophrenia had FRSs compared with 14 percent of
affective disorder patients. However, using a narrow definition of FRSs, the proportions were 73 percent and 6 percent, respectively. The index most commonly used to determine the diagnostic usefulness of a symptom is discriminability, a measure of the proportion of cases with the symptom who have the appropriate diagnosis. From the IPSS, the figures for FRSs are between 0.95 and 0.97 in schizophrenia compared with 0.02 and 0.03 in mania (Wing et al. 1974). Are the negative symptoms any more spedfic7 It seems unlikely considering the large number of functional and neuropsychiatric disorders in which psychosocial impairment occurs (Sommers 1985; Carpenter 1991). Chronic depression, substance abuse, personality disorders, epilepsy, and so on, all affect attentiveness, volition, and sociability. Empirical data on this are lacking because few studies have determined base rates for negative symptoms in heterogeneous patient groups. One such study found a higher prevalence of negative symptoms in depression than in schizophrenia (Kulhara and Chadda 1987). Andreasen and Flaum's article does not clarify this. The reference to Andreasen (1989) given in table 6 does not appear in the reference list and most of the studies in table 7 are either unpublished or not available in English. The one exception (Moscarelli et al. 1987) seems promising in that of a sample of 96 subjects, 59 (61%) were diagnosed as having schizophrenia. Unfortunately, much of the reliability data quoted are based on only 24 schizophrenic patients. The results in table 8 (presumably based on Andreasen 1985), plus those in the larger of the samples in table 9, are based on '111 consecutively admitted schizophrenic patients, most of whom had established chronicity . . . "
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negative features any more frequent 7 The Iowa results suggest not, the one exception being blunted affect (87%), which is already included in both ICD-10 and DSM-1U.
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Positive Symptoms Do Not Predict Outcome. Negative Symptoms Do. Andreasen and Flaum make two references to predictive validity. First, they comment on the poor prediction of outcome reported for the main current diagnostic criteria (Helzer et al. 1981, 1983; Endicott et al. 1986). In listing the virtues of negative symptoms, they include the prediction of poor outcome (Carpenter et al. 1978; Johnstone et al. 1979; Pogue-Geile and Harrow 1984, 1985). We see several possible misconceptions in what they imply. To start with, the diagnosis of schizophrenia, regardless of the details of diagnostic criteria, must surely reduce a person's overall functioning in comparison to the general population, otherwise its definition as a disease would be in doubt. Second, they confuse diagnosis with prognosis. It is not necessary for
diagnostic criteria to be prognostic indicators; these are separate, unless the outcome of a disorder is fairly uniform, which is far from true of schizophrenia. Third, any criterion that restricts diagnosis will improve predictive validity by creating a more uniform syndrome. Hence the 6-month criterion of DSM-III must improve prediction but only by a self-fulfilling maneuver, that is, by removing short duration illnesses from any patient sample. An allied source of confusion is between severity and prognosis. An illness that is more severe should have a worse prognosis and vice versa. Negative symptom patients have more cognitive impairment (Owens and Johnstone 1980), motor disorders, and tardive dyskinesia (Waddington et al. 1987). Moreover, any biological trait markers will be expected to be more prominent in more severe cases. Although the evidence is not unanimous, almost all biological markers seem to predominate in patients with negative symptoms. Such studies are reviewed in Andreasen (1990) and quoted with approval by Andreasen and Flaum in their article. To these could be added magnetic resonance imaging (MRI) studies of cerebral abnormalities (Williamson et al. 1991), information processing speed (Weiner et al. 1990), event-related potentials (Pfefferbaum et al. 1989), and visual-evoked potentials (Schwarzkopf et al. 1990), plus cerebral blood flow studies showing hypofrontality, which is invariably used to explain negative symptoms (e.g., Weinberger and Berman 1988). Because the bulk of studies all point in the same direction (rather than some markers consistently going along with positive symptoms), we take this as support for the severity explanation rather than as a validation for the concept of two schizophrenic syndromes, positive and negative. A pro-
spective study of patients with homogeneous negative symptoms, some of whom had, say, large ventricles, or alternatively, a cohort of mixed schizophrenic subjects selected on the basis of large ventricles would be necessary to determine whether either of these factors exerted independent effects on outcome. Another possibility is that positive and negative syndromes, while independent, may occur together. This situation is common (DeLeon et al. 1989) and of practical importance, but theoretically it is the least interesting. Assodations such as this do not allow strong inferences in psychology (Shallice 1988; David, in press), whereas dissociations, positive without negative symptoms and vice versa, prove that the two-symptom dusters cannot share a single pathological mechanism. Fourth, the nature of negative symptoms indudes, by definition, aspects of poor prognosis. Anergia, impersistence at work, avolitionapathy, and work inattentiveness are descriptions of patients who are currently not doing well in psychosodal rehabilitation, so their predictive power is spurious. A related problem arises out of Strauss and Carpenter's important finding (Strauss and Carpenter 1974) that premorbid adjustment is one of the strongest predictors of outcome—that is, some negative symptoms such as those above may not be symptoms at all but baseline levels of functioning. It may be the combination of these with schizophrenia that is so deleterious (see also Dworkin et al. 1990). In a recently published factor analytic study (Lenzenweger et al. 1991), schizophrenic phenomenology was best accounted for by a 3-factor model in which premorbid poor social adjustment is the third factor, quite independent of both positive and negative symptoms.
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(p. 41) so it is not surprising that this group had prominent negative symptoms (as well as delusions and hallucinations). Andreasen and Flaum obviously support the "radical change" introduced by the DSM, from viewing negative symptoms as a useful basis of subdassification to seeing them as central to the diagnosis. However, in 1982 Andreasen and Olsen wrote regarding the Scale for the Assessment of Negative Symptoms (SANS; Andreasen 1984): "Because these are criteria for subtyping schizophrenia, all patients must first meet DSM-III criteria for schizophrenia" (p. 790). This article went on to report reliability and validity data from 52 schizophrenic patients who had a mean of five admissions to hospitals with durations of over 12 months and histories averaging 8 years. Clearly the group was biased toward chronidty and was unlikely to include patients with uncertain diagnoses.
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Positive Symptoms Are Not Reliable. Andreasen and Flaum (1991) state: The literature currently supporting their [negative symptoms'] stability and validity is much stronger than the literature that can be marshaled in support of first-rank symptoms or probably even positive symptoms in general. Most existing evidence indicates that positive symptoms are neither internally consistent nor stable over time. (pp. 37-38] Several studies have examined the interrater reliability of symptoms in schizophrenia, and these are quoted in detail by the authors. The tables make it dear that, although good reliability has at times been demonstrated for negative symptoms also, the best reliability has been reported for positive phenomena, including those of first rank. Positive Symptoms Are Not Fundamental to Schizophrenia. With the advent of imaging technology and molecular genetics it is tempting to view phenomenology as irrelevant. However, no biological technique has come near the sensitivity and specificity of delusions and hallucinations for schizophrenia. For example, computed tomographic (CT) scanning, the most widely studied biological tool in this field, while showing group differences between schizophrenic and other psychiatric patients, also shows a large overlap between groups. Indeed, lateral ventricular enlargement
has been calculated as occurring in somewhere between 7 to 94 percent of schizophrenic patients (Smith and Iacono 1986). When medical controls are used for comparison, schizophrenic patients' ventricular brain ratios (VBRs) may be completely within the range of the controls. The sensitivity and specificity of CT scanning is therefore extremely low. While negative symptoms—in the Jacksonian scheme favored by Andreasen and Flaum—are understandable as a loss of normal functioning, positive symptoms, particularly FRSs, do not obviously reflect a normal function that has been disinhibited by disease. FRSs are outside normal experience—although apparently nonpsychotic people have reported hearing voices referring to them (usually by name) or hearing their thoughts echoed (Chapman and Chapman 1980; Posey and Losch 1983-84), this is rare and may be an artifact of the demand characteristics of certain questionnaires and interviews. When scrutinized, the reported experiences would not be classed as FRSs according to the Present State Examination (Wing et al. 1974). Jaspers emphasized the ununderstandability of these symptoms, which distinguished them from, for example, apathy and avolition. He wrote: The most profound distinction in psychic life seems to be that between what is meaningful and allows empathy and what in its particular way is ununderstandable, mad in the literal sense, schizophrenic psychic life. . . . Pathological psychic life of the first kind we can comprehend vividly enough as an exaggeration or diminution of known phenomena. . . . Pathological psychic life of the second kind we cannot adequately comprehend in this way. [Jaspers 1913/1963, pp. 577-578]
He continued: For lay persons madness means senseless raving, affectless confusion, delusion, incongruous affects, a crazy personality. . . . Holding these views the lay person has hit upon a basic difference within morbid psychic life which even today we cannot formulate clearly and precisely but which remains one of the most interesting problems. [Jaspers 1913/1963, pp. 577-578] Positive symptoms, especially FRSs, imply a breach in the sense of self and the integrity of thought. This, after all, is what most clearly marks schizophrenia as a pathological entity.
Conclusion Should DSM-IV be modified to give negative symptoms more prominence, to make the diagnosis of schizophrenia more likely when they are present and less likely when they are absent? The justification provided by Andreasen and Flaum is flawed in several places and the effect of such a change—a further restriction on DSM-III schizophrenia—is something they themselves wish to avoid. In their initial summary they go against the thrust of the text of their article by advocating prominence for both the positive and the negative. But this already exists. In both ICD-10 and DSM-III-R, blunting is specifically listed under the clinical criteria while in DSM-III-R social deterioration is a requirement. Certainly the negative symptoms need further investigation—their psychology, etiology and treatment—but their place in classification is already satisfactory. They add to the diagnosis of schizophrenia but do not detract from the importance of delusions and hallucinations, which, we contend, remain the essence of schizophrenia.
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Finally, the authors quote the study by Endicott and colleagues (1986) as confirming the poor predictive power of all the diagnostic systems they examined. They fail to mention that this study concluded that a composite of elements of DSM-1I1 and at least one FRS achieved the best predictive power, at least in the short term.
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The Authors Anthony S. David, MRCP, MRCPsych, is a Senior Lecturer, Department of Psychological Medicine, King's College Hospital, London, United Kingdom. Louis Appleby, MRCP, MRCPsych, is a Senior Lecturer, University Department of Psychiatry, Withington Hospital, Manchester, United Kingdom.
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