THE PSYCHIATRIST FACES many problems when classifying and diagnosing disorders. For example, the category ‘schizophrenia’ currently consists of a heterogeneous collection of interrelated and relatively distinct phenotypes. These variants relate to relatively distinct brain-behavioral modules, each with either overlapping or separate etiology, pathophysiology, course characteristics and treatment response. At present more than 100 combinations of symptoms can lead to a diagnosis of schizophrenia according to DSM-IV. Furthermore, the requirements that need to be fulfilled for a diagnosis of schizophrenia are not the same in the different diagnostic systems; for example, ICD-10 requires characteristic symptoms to have been present for at least 1 month, and DSM-IV for at least 6 continuous months, raising questions about the validity of each system. Studies have shown that the frequency of diagnostic groups in large patient samples not only depends on the diagnostic system applied but also on the particular version of that system. The schizophrenia/bipolar dichotomy has validity problems, because a large proportion of individuals fall into the overlap area between schizophrenia and bipolar disorder and are currently diagnosed as schizoaffective, or psychotic/mood not otherwise specified. At the moment people with schizophrenia are grouped into categories, whereas it may be more clinically relevant to group symptoms (e.g. positive symptoms, negative symptoms, depression, mania, cognitive decline and functional impairment) into dimensions. Some evidence suggests that a dimensional approach may be superior to a categorical approach in terms of clinical usefulness and prognostic ability, but the question of diagnostic usefulness is still to be clarified. Factors such as duration, time course and etiopathogenesis (e.g. emotional, cognitive, social) are important for the treatment and outcome of schizophrenia but are not covered by current diagnostic systems.1
In principle, numerous classification parameters – for example, etiopathogenesis, presentation, course, response to therapy and so on – and therefore various classifications of psychiatric disorders, are conceivable.2 Depending on the choice of classification parameters (e.g. Kraepelin's nosological system or that of the Wernicke-Kleist-Leonhard school), different classifications are produced, sometimes with different levels of abstraction (nosology, syndromatology). The classes arising out of these different systems are the result of an idealizing abstraction and selection process. They do not correspond to actually existing entities, but are theoretical constructs.3,4 The fact that there can be smooth transitions between the various classes, is mainly taken into account by the point of view that the classification of psychiatric disorders can basically be characterized by a typological approach.5–8‘Types’ include all of the features on which the similarities between the objects belonging to these types are based, even if some or even most of these objects do not exhibit all of the features that make up a particular type. Types do not exist in reality, but are developed from abstraction of real facts.
Apart from the division into classes, it is also possible to create a system of psychiatric disorders on a dimensional basis.9,10 In the simplest case such a system is one-dimensional, because it consists only of a continuum ranging from an optimal social adaptation to the most severe degrees of psychosocial disintegration. By contrast, multi-dimensional systems are mainly based on several personality traits or behavior patterns. Eysenck, in particular, starting from multivariate statistical analyses of questionnaires on personality traits, propagated a dimensional system of psychiatric disorders.9 Phenomena were arranged on a continuum described by certain dimensions; Eysenck suggested neuroticism, psychoticism and introversion/extraversion.
Irrespective of whether a dimensional or a categorical classification system of psychiatric disorders corresponds to reality, all dimensional classifications merge into a categorical or typological classification when certain degrees of manifestation of certain behavior patterns are rated as ‘mentally ill’ or as diagnostically, therapeutically or prognostically relevant, based on statistical averages. Of course, based on this approach also cases of a ‘full syndrome’ can be differentiated from ‘subsyndromal’ cases. The main types of psychopathological phenomena then could be rated as ‘extreme types’ of certain personality traits or behavior patterns, as Eysenck demonstrated. In Eysenck's psychopathological classification system, which attempted to describe the main types of psychopathological phenomena as extreme variants of normal personality traits, hysteria, for example, is characterized as a combination of extreme neurotic tendencies and extraversion, and schizophrenia as a combination of extreme psychoticism with neurotic tendencies and introversion.
We should bear in mind those basic principles of a systemization of psychiatric disorders2 to better understand the possibilities, problems and limitations of the current process of revision, the internationally used classification systems ICD-10 and DSM-IV.
Work on the revision of the present psychiatric classification systems (International Classification of Diseases of the World Health Organization [WHO], at present version 10 [ICD-10], and Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association [APA], at present the fourth revision, DSM-IV, to be more precise, of DSM-TR) has been ongoing for the past several years. The goal is to publish the new versions ICD-11 and DSM-V in approximately 5 years' time. Increasingly, these two processes are being coordinated, the aim being to keep two separate classification systems, the main features of which, however, will be identical.11 For psychiatry as a clinical field of expertise, this revision is of great importance but could also be problematic, because not only small formal adaptations are planned, but fundamental reforms that affect the foundations of psychiatric nosology and classification.
It is obvious from the foregoing that the revision processes on the part of WHO and the APA/National Institutes of Health (APA/NIH) are well under way. While in the USA the focus is more on the identification of scientific evidence for new classification criteria, WHO's approach is clearly influenced by health-care issues. Although the two approaches are to a certain extent complementary, we should keep sight of the goal, which is harmonization of the two classification systems.
The following article deals with some principal aspects of the development of the new classification systems, the focus being on the following issues: (i) the basic question: categorical versus syndromatological system of psychiatric disorders; (ii) procedure and proposals for changes in the development of ICD-11 and DSM-V; (iii) is a fundamental change, for example the combination of schizophrenia and bipolar disorder into a psychotic continuum in the psychiatric classification meaningful with the present state of knowledge; and (iv) is there still a major role for the classical sophisticated psychopathological approach beside a neurological approach.
PRINCIPAL ASPECTS OF CATEGORICAL AND SYNDROMATALOGICAL SYSTEMS OF PSYCHIATRIC DISORDERS
In the development of the new classification systems, and especially in the discussion on DSM-V, particular attention will be paid to the principal question of whether the present categorical psychiatric classification or a syndromatological classification will be judged to be more meaningful. A possible compromise could be a combination of both categorical and syndromatological elements. Besides a more precise description of the psychopathological picture of individual cases, this would help in dealing, among others, with sub-threshold cases.
Syndromatological classification can be seen as an alternative or addition to nosological classification.2 By ‘syndrome’ we mean the combination of certain symptoms appearing together cumulatively. As opposed to nosological classification, a syndromatological classification of cases is limited to a cross-section view and pools cases based on the presence or absence of certain syndromes.
Despite the existence of Kraepelin's categorical system, the syndromatological factor continued to remain in focus due, among other things, to the Bonhoeffer criticism that Kraepelin's approach was deficient.12,13 Especially recently, the syndromatological classification or a syndrome-focused dimensional system is being given more attention again. This is connected among other things with the criticism of nosology, which according to some authors is not sufficiently empirically based, and in particular also the criticism of Kraepelin's dichotomy of functional psychoses in dementia praecox (schizophrenia) and affective disorders (Palm and Möller, unpubl. data, 2009).14 The syndromatological classification of psychiatric disorders arose on the basis of clinical intuition. It describes the joint occurrence of symptoms without considering the conditions of their origins; for example, paranoid-hallucinatory syndrome, depressive syndrome, manic syndrome, amnestic syndrome, among others. Psychopathological syndromes are unspecific with respect to the etiopathogenetic factors on which they are based: the same syndromes may have different causes, and the same causes can result in different syndromes.
Statistical methods to investigate the accumulated joint occurrence of single symptoms are factor and cluster analyses. The data on which evaluations performed with these methods of multivariate statistics are based are obtained from psychopathological findings recorded with rating scales.15
A syndromatological classification of cases can be achieved based on these syndromes on the basis of multivariate statistical analyses of patient samples by combining several syndromes, each of a certain degree of expression, to typical syndrome profiles. Such syndrome profiles allow the creation of diagnostic groups based only on the similarities in the profile and without considering the clinical diagnosis.
A syndromatological classification with syndrome profiles on the basis of rating scales appears to be advantageous for various reasons: development of more precise diagnostic algorithms, greater reliability, and greater ability to differentiate through quantifying presentation of syndrome profiles. But if it is only related to symptom patterns, a syndromatological classification cannot completely replace a nosological classification because it does not consider etiology, course and response to treatment – information that is extremely important for therapy and prognosis. Under this aspect the diagnosis of a syndrome is only rarely used as a final diagnosis but rather as a reliable step on the way to a nosological diagnosis. This will also need to be taken into consideration in the present discussion of the plans for DSM-V and ICD-11.16
It was questioned whether even syndromes are too complex and not meaningful entities when researchers want to find associations, for example with causal neurobiological parameters. This might be principally meaningful from the perspective of neurobiological research, but could also lead to complications, for example in terms of reduced interrater reliability on the symptom compared to the syndrome level. Also, an increasing risk for statistical findings by chance given the high number of symptoms in patients having a certain disease, when all symptoms are correlated with a neurobiological parameter, should be considered. Keeping in mind that van Praag's ‘functional psychopathology’ focuses primarily on the serotonin system, associating with disturbances of this system with obsessive–compulsive symptoms, aggression and so on, it should also be considered that the neurobiological causation of symptoms is often complex and involves more than one transmitter system. For example, recent research has demonstrated that obsessive–compulsive symptoms are apparently not only associated with disturbance of the serotonergic system but that disturbances of the dopamine system might also be involved. The proposal of a ‘modular system’ of psychopathology17 has some similarities with the ‘functional psychopathology’, but it focuses not on transmitter systems but on neurophysiological/neuropsychological concepts. It must be further investigated whether it can fulfill the aim of giving an improved explanatory and classificatory approach. Recently, also from a genetic approach, an attempt was made to find associations between genetic alterations and symptoms/syndromes. The findings focused on the 72 gene. Interestingly, three research groups found three totally different associations.18–20 This underlines the fact that associations on a genetic basis with clinical symptoms/syndromes might not be easier to find than associations with higher disorder entities. If one tries to understand the relationship between genes and clinical phenotypes on the disorder or syndromatic level, this does not seem astonishing. A gene modulating different (neuro-)biological functions can in the end have an impact on the causation of different syndromes/symptoms depending on the functions that are modulated.21
There is some hope that endophenotypes, which in contrast to symptoms are more stable and persistent, could be better targets for associations with disorders or syndromes.22–25
In addition to symptoms, the nosological classification of psychiatric disorders considers the course and response to therapeutic procedures and, if known, the etiology and pathogenesis of the symptoms. Owing to the greater complexity that results from the inclusion of so many factors, particularly known and suspected etiopathological factors, there are significantly more divergent attempts at classification where nosology is concerned than in the area of syndromatology.2
The traditional nosological classification systems of psychiatric disorders, like the syndromatological systems, arose on the basis of clinical intuition. First the individual disorders were identified and described (nosography), then an attempt was made to organize the described disorders into a clear three-tiered classification system (nosological classification). It is apparent that such a procedure is bound to be logically incongruent. The nosological classifications commonly used in psychiatry today are based on the classification designed by Kraepelin26 and developed from the approaches of Kahlbaum27 and Schüle.28
Kraepelin categorized the main groups of disorders according to causal factors, most of which, however, were to a great extent hypothetical, and some of which still are. Bonhoeffer's discovery that different somatic causes can give rise to the same psychopathological symptoms, and that the same cause can give rise to various psychopathological symptoms,12 was the basis for subsequent fundamental criticism of Kraepelin's nosology (Palm and Möller, unpubl. data, 2009). Nevertheless, the basic features of his nosology still became accepted worldwide and are still accepted to this day. The non-specificity of psychiatric disorders with respect to the causal factors was later interpreted as a result of interference by several etiopathologically relevant factors (genetic disposition, primary personality, biography, poisons etc.).29,30 In this context one refers to the multiconditionality of psychiatric disorders.
Not only was the basic conception of Kraepelin's ‘disorder units’ repeatedly questioned, but also his special nosological classification was criticized. The critics favored either the extreme of a pooling of the generally differentiated forms of endogenous psychoses as an Einheitspsychose (unitary psychosis),31 or propagated the other extreme of their dissolution into numerous special forms according to genetic symptoms and course.32,33 Besides this lumping-together approach, there was also the opposite, the splitting approach, which propagated the other extreme of the dissolution into numerous special forms according to genetics, symptoms and course.32,33
Modern twin and family genetic studies, as well as studies of course and neuropathology, give insufficient support to the concept of a uniform psychosis because affective psychoses can be differentiated from schizophrenia psychoses at least to a certain degree with respect to genetic aspects, brain neuropathology and the course of the disorders.3 The categorization between schizophrenic and affective psychoses and the differentiation of the other diagnostic entities might therefore not fully reach the demands of a clear-cut categorical system; and there might be reasons enough to continue with these concepts at least in a typological sense. Although the ‘point of rarity’ as an indicator for a categorical/typological differentiation34,35 in the distribution of relevant symptoms or other variables might be missing, many experts, especially from the field of basic science, currently find it more interesting to omit these diagnostic entities and develop a new systematics, primarily based on parameters of basic science than on clinical observations. With respect to further differentiation, the concept of schizoaffective psychoses as a special type between schizophrenic and affective psychoses is generally seen to be supported by some family genetic and catamnestic findings. The differentiation between unipolar depression and bipolar (manic–depressive) psychoses can be seen to be established on the basis of empirical findings.
A so-called multi-axial classification was conceived for ICD-10 to include, among others, etiological aspects in a more differentiated way. A single (as opposed to the ninth revision, in which several numbers were used) multi-digit number describes the patient's disorder. The individual points of the number correspond to the so-called axes that represent symptoms, severity and etiology and so on.33,36–39 The description of this classification, however, as multi-axial or multidimensional is misleading, because the ‘axes’ of this system do not represent dimensions reflecting different degrees of expression, but rather an arbitrary row of various aspects. Nevertheless, an obvious advantage of such a classification is that syndromes are used to describe the clinical presentation instead of nosological categories, as is the case at present, which always include a hypothesis on the cause. Every syndrome can be combined with every cause that in principle could come into consideration. The disadvantage is the enormous number of combination possibilities, which perhaps corresponds to reality but which in the end becomes unmanageable.39–41 In addition, the relationship between various aspects implied in a nosological classification is possibly obscured. These could be the reasons why the multi-axial classification proposed in ICD-10 did not meet with much response in daily clinical routine and in the end was not adopted in a scientific context.
Psychiatrists usually tend to assume that a nosological diagnosis includes more information and as a consequence also has more predictive power than a syndromatological diagnosis. Recent findings, however, demonstrated that the categorical differentiation between schizophrenic and affective psychosis was not of better predictive value for long-term outcome, and even that a prediction based merely on syndromes or the syndromatological approach was superior.42–44 In this context the study by Allardyce et al. is also of interest because it demonstrated different patterns of association between either categorical diagnoses or dimensional representations of known risk factors for psychosis.45
PROCEDURE AND SUGGESTIONS FOR CHANGE IN THE DEVELOPMENT OF DSM-V AND ICD-11
Development of DSM-V
The leading body in the development of the US classification system of psychiatric disorders is the American Psychiatric Institute for Research and Education (APIRE) under the direction of D. Regier, with the precise goal of publishing DSM-V in 2012. By then 18 years will have elapsed between DSM-IV and DSM-V. The development of DSM-V was started in 1999 with cooperation between the APA and representatives of the NIH, resulting in a research agenda with suggestions for research projects as preparation for DSM-V.46 Based on this, between 2004 and 2007 a series of research conferences on all the main topics in the field of psychiatry were held. These conferences were organized jointly by APIRE, the competent NIH institutes and WHO. Special attention was paid to international participation at these conferences, with approximately half of the speakers coming from outside the USA.47
It was planned that international up-to-date results relevant to the classification of psychiatric disorders should be presented at these conferences. In addition, new research questions should be formulated that could then be clarified in the 5 years remaining before the publication of DSM-V. In general, a trend towards dimensional instead of categorical classification criteria could be identified early, so that an additional conference especially devoted to this topic was included in the series of conferences. This conference focused on feasibility analyses regarding dimensional diagnosis systems exemplified by six chosen disorder groups. It was understood that the dimensional diagnosis systems do not necessarily simplify the diagnosis, but in some cases may even induce new complex demands on the clinical diagnosis. In addition to these research conferences, discussions on the ‘Kraepelin dichotomy’, which are documented, for example, in the Schizophrenia Research Forum on the Internet (http://www.schizophreniaforum.org/for/live/) and in the journal of the World Psychiatric Association (WPA) World Psychiatry (June 2007),48 took place and a consensus already seems to have been reached that at present there are not enough data available for a revision of the classification criteria or for the declaration of a nosological revolution. A consensus, however, was reached that genetic risk factors transcend the traditional boundaries between schizophrenic and affective disorders, so that they are more predisposed toward more precise clinical types or psychopathological phenomena than toward classical psychiatric diagnosis groups. In classification systems this could be reflected through, for example, an additional relationship to functional–psychopathological dimensions.49
In April 2006 the APA officially appointed D.J. Kupfer and D.A. Regier as Chairman and Vice-Chairman of the APA Task Force on the Revision of DSM-V. This task force consists of 13 diagnosis-specific working groups and 15 representatives from research and clinical practice. In January 2007 WHO assembled an 11-member Committee on the Development of ICD-11. These committees will now also organize the process of coordinating content.
A wealth of methodological and contextual topics has been dealt with at the research conferences in preparation of DSM-V. It is not easy to summarize these topics because the individual research conferences have used different approaches to the problems involved. For the working groups using a primarily methodological approach the focus was on the following aspects, among others, as listed in Table 1.
Table 1. Topics under discussion in preparation for DSM-V
|Methods in psychiatry|
|• Which criteria should be used to decide whether dimensional versus categorical approaches should be used|
|• Lack of gold standards for validation|
|• Importance of comorbidity for classification|
|Role of dimensional classification|
|• Dimensional scales have been proposed for six main categories of psychiatric disorders in terms of a feasibility analysis (ADHD, personality disorders, addictive disorders, anxiety disorders, affective disorders, psychotic disorders)|
|• Recommendation on the reduction of the time criterion in schizophrenia to 1 month or for the analysis of ‘psychosis’ the best time criterion in studies with monthly follow up|
|• Studies on the introduction of a ‘general psychosis syndrome’|
|• Inclusion of dimensional diagnostic criteria and discussion of alternative systems50|
|• Retention of the differentiation between schizophrenic and affective psychoses for the time being51|
|Stress and anxiety disorders|
|• morphology of the amygdala, hippocampus and frontal lobe|
|• mapping of anxiety conditioning in neuronal systems|
|• correlation of imaging and clinical results|
|• genetic factors|
|• carrying out multimodal clinical studies|
|• Proposals for a new categorization of compulsive disorders on the basis of the criteria phenomenology, comorbidity, family anamnesis, frontostriatal function and response to therapy|
|• Compulsive disorders and anxiety disorders should be classified separately|
|• Proposals for new clinical criteria of ‘compulsive’|
|• Construction of a battery of endophenotypes50|
|Somatic manifestations of psychiatric disorders|
|• Necessity for a new definition of ‘somatic distress disorder’, e.g. with inclusion of user and operator as well as studies in the area of the primary physician, the goal being to simplify the diagnostic categories.|
|• Categorical versus dimensional diagnostics|
|• Neurobiological basis|
|• Social and cultural aspects|
|• Special problems with adolescents|
|• The role of non-substance-related addiction.52,53|
|• Development of international criteria to define ‘daily activities’|
|• Genetic markers are not yet adequate for the diagnosis of Alzheimer's disease.|
|• Apart from biomarkers 14 to 3-3 for Creutzfeld–Jakob disease no biomarkers have so far been adequately validated.|
|• Renunciation of disturbance of memory as the main symptom, and instead reduction of two cognitive areas for >1 year.|
|• Development of positive diagnostic criteria for Alzheimer dementia.|
|• Better investigation of risk factors.|
|• Increasing the number of autopsies.54|
Development of ICD-11
ICD-10 is updated annually, and every 10 years a complete new version is published.55 In future, so-called ‘cumulative updates’ will be published every 3 years. As with the APA, proposals for change can be submitted any time via the Internet. The revision process leading to ICD-11 is also taking shape now. The ICD-11 draft version is to be prepared in a Wikipedia-like ‘joint-authoring process’, whereby expert groups will be the authors of the first version. A WHO guidance group will carry out the coordination centrally, and there will be advisory boards of expert representatives for the different disorder groups. Not only the classification of psychiatric disorders will be revised, but also other issues will be taken into consideration. For example, recently, the expert group for mental health was established.11 A working group will be formed for each mental core disorder, for example schizophrenia and psychoses, affective and anxiety disorders, general brain disorders, among others. These groups will formulate preliminary position papers and critically assess the empirical evidence. They will report to the coordinating group and evaluate feedback from among Internet users and scientific publications. The WHO places great value on response even in the early stages of the development of ICD-11, and for this purpose will establish an open-access Internet platform. The preliminary diagnostic criteria developed out of this feedback process will then be evaluated in large field studies.
Regarding content, the following tendencies and problems in the development of psychiatric classification criteria for ICD-11 can already be discerned11: (i) the hypothesis of the universality of psychiatric classification criteria will no longer be unequivocally accepted, especially with regard to the inclusion of culturally specific aspects; (ii) tension is expected regarding the suggestion to include user circles in the development of ICD-11; (iii) the registering of conflicts of interest due to possible influences on the part of the pharmaceutical industry; (iv) should ICD-11 be developed further in terms of a textbook, possibly even with recommendations for treatment; and (v) addressing the question of the public health system in the revision process by the WHO, particularly regarding inadequate care of the mentally ill in some countries; what impact will revised diagnosis criteria have on this situation.
B. Saraceno (Director of the Department of Mental Health and Substance Abuse at WHO in Geneva) considers it important that newer data on the nosology of psychiatric disorders are reappraised and that not only classification criteria are newly defined.11 There is a WHO working group headed by N. Sartorius whose task is to include school- and language-specific features in the revision process. In addition, a WHO committee on the development of the psychiatric part of ICD-11 was established to deal with questions regarding the harmonization with the DSM-V process (but also the classification systems in use in China or Latin America), psychopathological and methodological questions, and terminology-related issues, as well as the differential wishes of the primary caregivers versus the caregivers in the highly specialized field of care. The psychiatric section of ICD-11 is intended for clinical use, for use in research, for education, for the advancement of public health and for statistical use. In this context WHO has also raised the question of categorical versus dimensional classification systems, whereby questions of threshold values are to be addressed here initially. In addition, the differences between ICD-10 and DSM-IV-TR will be reassessed and the scientific evidence for the present disorder groups reappraised. A first draft of ICD-11 is expected to be available already at the end of 2008. Following an international review of this version, the beta version will then be tested in field studies in 2011, from which the final version will be developed and approved in 2014.56
After a process of consensus lasting several years it may be that the field of psychiatry and psychotherapy will be faced with completely new classification systems. Questions on the validity of psychiatric classification criteria, the controversy between ideographic (psychodynamic–biographical) and neurobiological–natural science concepts, the question of universal versus culture-specific and the dimensional versus categorical classification, but also the demand for practicability, are on the agenda. Can new scientific knowledge already be included now in the classification criteria, and how can clinical–pathological experience, endophenotype research, psychiatric genetics, environmental influences and possibly even response to treatment be accommodated within a new classification system? How can – as called for by the WPA – individual–biographical elements in terms of a ‘psychiatry for the person’ be included?
It is still unclear as to what extent the present trend towards a biologization of diagnostics in the field of psychiatry and psychotherapy will be reflected in the new classification systems. Hopes are high that from a better understanding of the neurobiological basis of psychiatric disorders in the end also treatment forms oriented towards etiopathogenesis can be developed. At present the results of the research conferences indicate rather that no revolution in psychiatric classification can be expected here. Although there is an abundance of single results from various areas of neurobiology such as brain imaging, psychiatric genetics and psychophysiology, they cannot yet form the basis for a new psychiatric classification.
In contrast, there is a tendency, originating from the WPA, towards ‘personal psychiatry’, which increasingly aims to include ideographical components in psychiatric diagnostics again.57 The representatives of both sides, however, are in agreement that empirical evidence is necessary, in order to include such criteria in the psychiatric classification systems. Purely narrative components without proven prognostic or therapeutic relevance will not be accepted internationally.
IS A FUNDAMENTAL CHANGE IN PSYCHIATRIC CLASSIFICATIONS MEANINGFUL WITH THE PRESENT STATE OF KNOWLEDGE?
There are chances and risks involved in a new classification of psychiatric disorders.58 The chances lie in the possibility of being able to clarify now the problems posed by transitional and in-between categories, to give the reliability and validity of diagnostic criteria a stronger basis through new research projects, and to include new knowledge from genetics and neurobiology in the classification system. The risks lie particularly in a further reification of hypothetical disorder constructs resulting from the operationalization of psychiatric diagnostics,51 but also from a loss of psychopathological knowledge due to diagnostics oriented solely towards an operationalization.59
Only a few main aspects of the present ideas for change can be discussed in the following section.
Recommendation of a purely dimensional (syndromatological) system and its complex of problems
A switch to a dimensional approach, which was discussed especially as one future direction of psychiatric classification in the context of the current discussion of DSM-V (among others in the DSM-V task force Deconstructing Psychosis) would be the most radical development. It could avoid many theoretical pre-assumptions about causal hypotheses that are still associated with ICD-10 and DSM-IV, although these classification systems claim to be nearly atheoretical and call for a primary syndromatic approach. This would indeed increase the validity of psychiatric classification, but it would also reduce the information of the traditional diagnostic categories with all their current implications concerning etiopathogenesis, therapy and prognosis. Among others it could have the following consequences: (i) acute depression would no longer be classified in terms of unipolar depression, bipolar depression and depression in the context of schizophrenia and so on; (ii) depression with psychotic symptoms would no longer be classified in terms of delusional depression (unipolar or bipolar), schizoaffective disorders, schizophrenia; (iii) acute psychosis would no longer be classified in terms of acute polymorphic psychosis, schizophreniform psychosis, affective psychosis and so on; and (iv) psychoses would no longer be classified into organic and non-organic psychoses.
Such a dimensional approach would require for the syndromes to be assessed in a standardized way for each person looking for help in the psychiatric service system or for each person undergoing psychiatric research. This would have to be a multidimensional assessment covering all syndromes existing in different psychiatric disorders. This goes further than the use of scales such as the Positive and Negative Syndrome Scale or Hamilton Rating Scale for Depression or a combination of both, but a comprehensive psychopathological assessment system such as, for example, the Association for Methodology and Documentation in Psychiatry (AMDP) system, a comprehensive assessment instrument based on the tradition of European psychopathology (Läge et al., unpubl. data, 2009),60–62 would be required as a minimum. This would mean a lot of work in routine care situations, which might not be feasible for pragmatic reasons. In this context it should be kept in mind that each person with a psychiatric disorder cannot be described by only one syndrome but may show different syndromes, which we know from the traditional diagnostic categories, among others.
As to a purely symptoms-oriented dimensional approach it should be understood that a certain score value does not mean very much in the clinical sense, but should be interpreted in comparison with normal values from a representative sample of the average population or to reference values from psychiatric patients. For example, a low score in a depression scale might not mean much in comparison to a normal value, because there is a considerable level of depressiveness in the average population.15 But a low value of a paranoid score can be an indicator for a severe disturbance, because the level of paranoid symptoms is extremely low in the average population. There are not many reference data, however, from representative samples available and naturally the norms from one country cannot be used as an indicator in another country. Much research would be necessary to develop these norms.
Switching to a purely dimensional approach in DSM-V/ICD-11 would induce a lot of uncertainty about treatment indications, especially regarding psychopharmacological treatment. Current decision-making concerning drug treatment of psychiatric disorders is related to both the syndrome and the psychiatric disorder.63 For example, for unipolar depression a different drug treatment approach is used than for bipolar depression. A depressive syndrome in the context of schizophrenia is treated differently than a depressive syndrome without schizophrenia. Without going too much into detail, the clinical decision-making for psychopharmacological treatment is simply not as easy as saying ‘use an antidepressant for depression’. There is much more to it than that (Möller et al., unpubl. data, 2009).
Recommendation to establish a psychosis continuum
Based on all these considerations regarding the introduction of a syndromatologically oriented dimensional system, which were considered by the experts involved in the development of ICD-11 and DSM-V, it seems that currently a categorical approach will be continued, and combined with a dimensional subtypology/subdifferentiation.49,64 But all validity problems of such a categorical classification will also continue. This includes not only the intensely questioned validity of the dichotomy between schizophrenic and affective disorders, and especially bipolar disorders, but also the dichotomy (it is interesting that this term is not used in this context) between depression and anxiety disorders or especially generalized anxiety disorder (GAD) and the distinction between GAD and panic disorders, all of which has not been discussed as much, and which should be focused on.
An often-named reason for the necessity to revise ICD-10 and DSM-IV is the increase in knowledge over the past 20 years, especially regarding neurobiological knowledge. But is this increase in knowledge, for example in the field of neurogenetics, of such a size that it makes a revision of our psychiatric classification necessary and promises to be fruitful? All the findings, although important for a deeper neurobiological understanding of psychiatric disorders, still seem to be on such a level that a new classification cannot be based on them.15 There is of course an overlap of the genetic risk factors for schizophrenia and bipolar disorder, and to a lesser degree for unipolar disorders. But does this doubtlessly lead to the assumption of Einheitspsychose, given the inconsistency of all these genetic findings and the small amount of variance explained by the hypothesized susceptibility genes? Should not the differences in outcome between schizophrenic and affective disorders continue to play a major role in the differentiation of both diagnostic groups as long as we cannot base a classification on sound and consistent neurobiological data?65
Because most psychiatric disorders lack clear biological correlates, follow-up studies on their course, outcome and prognosis are traditionally viewed as playing an important role in psychiatric research, especially in terms of validation of psychiatric diagnoses and other psychiatric concepts, for example negative symptoms.3 Only a few studies have addressed the differences between the course of schizophrenia and that of other psychiatric illnesses. These studies come to the same conclusion that the course and outcome of schizophrenia is less favorable than those of affective and schizoaffective disorders.66
In a 15-year, long-term, follow-up study on first-hospitalized patients, we used a comparative approach to assess course and outcome in terms of psychopathological and psychosocial aspects for 197 patients with schizophrenic, schizoaffective and affective psychoses.65
All available sources of information (interviews with the patient, their relatives and treating physician, medical records) were included in the classification of the course type. A chronic course was defined as follows: during the course of the disorder there was never a complete remission of symptoms, and/or further episodes of a functional psychosis occurred. The Global Assessment Scale score was consistently lower than 61 in the 2 years before the follow-up study. A total of 57% of patients with a diagnosis of schizophrenia were found to have a chronic course, but only 3% of patients with affective disorders and 15% of patients with a schizoaffective psychosis had a chronic course.
Analysis of the psychopathology scales of the Munich 15-year follow-up study found that patients with a diagnosis of schizophrenia had significantly more negative symptoms after 15 years. This became especially clear when results were analyzed according to the concept of a deficit syndrome,67 which describes chronic negative symptoms persisting for at least 1 year that cannot be explained as being secondary effects of extrapyramidal or depressive symptoms or of social deprivation.65,68,69
The question remains whether great importance should be placed on aspects of course for the differentiation of different groups of non-organic psychoses or whether other parameters, for example neurobiological ones, are more suitable to define valid and, with respect to biological factors, meaningful diagnostic entities. In his commentary on long-term studies Kendell wrote: ‘Despite its many imperfections, the concept of schizophrenia is unlikely to be abandoned until we have radical new insights into the etiology of the “functional psychosis” ’.34,49 Is the familial cosegregation of schizophrenia and bipolar disorders70 such a radical new insight that it justifies abandoning the concept of schizophrenia and the Kraepelinian dichotomy?
If the aim is to define disease symptoms on the basis of neurobiological parameters, neurobiology, particularly in the context of follow-up studies, should not only be understood in the sense of neurogenetics and molecular biology but should also include neuropathological findings or their in vivo surrogate findings,71–81 magnetic resonance imaging (MRI), together with results from neurophysiological evaluations and so on.81–86 For example, the results of structural MRI research show not only that patients with schizophrenia disorders have marked alterations in brain structure, for example ventricular enlargements and hippocampus atrophy, even in the premorbid stage – which can be interpreted as corresponding with the neurodevelopmental hypothesis81,85,87–89– but also that further brain alterations can occur during the course of the disorder.90–95 These structural brain changes are interpreted as being the result of progressive neurobiological processes of unexplained cause, which may be associated with immunological processes96 or changes in the glutamatergic system or other parameters. Although such alterations of brain structure are also found in patients with affective disorders, they are not so pronounced and evidently not or only to a minor degree progressive.97,98 Both in terms of neurodevelopment aspects99 as well as in terms of a neuroprogressive process schizophrenia might be dissimilar to affective disorders.
Problem of cosyndromatology/comorbidity
The traditional hierarchical approach to psychiatric classification in the sense of Jasper's layers rule (Schichtenregel) gave more weight to those symptoms that he interpreted as being the most relevant in the diagnostic hierarchy, for example a patient who suffered from schizophrenia and depressive symptoms was diagnosed as having schizophrenia.100 One of the implications of this principle was that, in most cases, a patient was given only one diagnosis. The development of the operationalized diagnostic systems ICD-10 and DSM-III/IV changed this strategy. Nowadays, a patient can be diagnosed as having several disorders simultaneously, if the relevant symptom- and time-related criteria for the particular clinical diagnoses are fulfilled. Comorbidity has thus become a central issue of current psychiatric classification.101 If the criteria for a certain disorder are not completely fulfilled, a subthreshold comorbidity can be considered. The epidemiological studies performed during the development of the DSM and ICD-10 systems paid great attention to the principle of comorbidity and proved empirically that if this approach is followed, there is a high degree of full or subthreshold comorbidity with other psychiatric disorders in almost all psychiatric disorders, including schizophrenia psychoses.
Although the concept of comorbidity seems principally meaningful if it describes the coexistence of two clearly separated entities, for example schizophrenia and alcohol addiction, this approach leads to an inflation of diagnoses when it comes to disorders with a rich picture of different symptoms, as is the case with schizophrenia. The modern diagnostic systems describe the simultaneous existence of several syndromes as comorbidity, although it could actually be better described as cosyndromality, given the fact that these syndromes are apparently not independent of each other but are often covariate over time. This kind of comorbidity was criticized for disrupting the coherence of the complex phenomenology of these disorders and for inducing the idea that each of these comorbid disorders might have to be treated with a different drug.102
The principal problem can be exemplified by using schizophrenia as a model. Schizophrenia is not only characterized by a paranoid–hallucinatory syndrome but typically also by a negative syndrome. Schizophrenia is therefore a cosyndromatic condition per se and its clinical picture is also enriched by other syndromes not belonging to the core/pathognomonic symptoms, for example depressive symptoms.2,100,103 If a comprehensive rating scale such as the AMDP system is applied, which covers more or less all relevant symptoms of the psychopathological spectrum of schizophrenic and affective psychoses,104–111 the complex psychopathological pattern of schizophrenia patients in terms of cosyndromatic conditions becomes obvious. The similarities and dissimilarities of the syndrome profiles become evident when schizophrenia patients are compared with schizoaffective and affective patients, who are also often characterized by several syndromes. The change in the mixture of the cosyndromatic conditions can be demonstrated in follow-up studies with cross-sectional ratings at certain time points.
It is a question of diagnostic tradition or current diagnostic consensus, and therefore to a large degree arbitrary, whether the coexistence of several psychopathological syndromes is conceptualized as cosyndromatology or comorbidity. The same is true for the criteria related to symptom intensity or configuration of symptoms as well as for time-related aspects of the appearance of symptoms, which are used in this context to describe a comorbidity. Apparently, DSM-III/IV and ICD-10 apply different strategies in dealing with this in the context of different disorders. For example, other principal rules appear to be applied for the differentiation of schizophrenia and depression than for differentiation of depression and anxiety, which leads to principal differences in the possible amount of comorbidity.
In addition to cross-sectional cosyndromality/comorbidity, which has been referred to in the previous section, there is also a longitudinal comorbidity, that is, lifetime cosyndromality/comorbidity. To use again the example of schizophrenia, in the sense of the traditional theoretical concepts of schizophrenia, depressive symptoms occurring before the appearance of positive symptoms would be seen as prodromal symptoms of schizophrenia, when occurring simultaneously as depressive symptoms accompanying the positive symptoms of the acute schizophrenic episode, and when apparent afterwards as a post-psychotic depression occurring after the positive symptoms have abated. With the comorbidity approach these depressive symptoms can apparently become independent ‘disorders’/‘illnesses’, as long as the relevant ICD-10 and DSM-IV criteria are fulfilled. On the one hand this has the advantage that certain subtypes or special forms of the illness can be more easily defined and investigated. On the other hand, for everyday clinical practice this conceptualization has the disadvantage that the concept of schizophrenia, which was assumed to be homogeneous, is broken up into many sub-aspects and the inner relationship of the distinct syndromes becomes harder to understand. Although this is also true for cross-sectional comorbidity, it becomes even more obvious in the example of lifetime comorbidity.112 DSM-IV and ICD-10 try, as far as depressive symptoms are concerned, but not concerning anxious or obsessive–compulsive symptoms, in the context of schizophrenia to avoid as much as possible such a negative consequence. They therefore include under cross-sectional and longitudinal aspects depressive symptoms almost as widely as part of the concept of schizophrenia, whereas concerning other disorders such as, for example, depression, obsessive–compulsive disorder and anxiety disorders there is a much higher tendency to apply the concept of comorbidity.
The coexistence of psychotic (schizophrenic) symptoms and depressive/manic symptoms can lead to a major diagnostic dilemma: can the coexistence of these symptoms be seen as an integral part of schizophrenia or affective disorders? Is this a comorbid condition? Is this related to a special disorder such as schizoaffective psychoses? Is the differentiation between mood-congruent and mood-incongruent psychotic symptoms of relevance in this context?
Schizoaffective psychosis is a special example of the close interlocking of schizophrenic and affective (manic, depressive) symptoms in the stricter sense. It was traditionally not only conceptualized as a cosyndrome or comorbidity but as the result of an etiopathogenetic amalgamation process between schizophrenic and affective disorders, which may be supported at least partially by family–genetic and also other etiopathogenetic findings. The mere description in terms of cosyndromality or comorbidity would not reach the full content of this concept. The repeatedly discussed unitary psychosis (Einheitspsychose), which fully combines the schizophrenic and affective psychosis as belonging to the same continuum of psychosis113 with a common etiopathogenetic background, can be seen as the extreme of this conceptualization.50,114–119
Apart from the historical development of the concept, the current conceptualization by the ICD-10 and DSM-IV criteria120,121 represents a special type of the relevant modern conceptualization of a relationship between schizophrenic and affective symptoms. The affective part occurs either simultaneously with the schizophrenic symptoms or sequentially (without concurrent schizophrenic symptoms), depending on the diagnosis system applied.122 There is no referral to comorbidity with an affective disorder but the conceptualization of a schizoaffective psychosis covers the whole range of phenomena through the term ‘schizoaffective psychosis’ itself. The earlier the prototype of a coexistence with bipolar affective symptoms becomes apparent, the more justified the concept appears. If the depressive symptoms simply coexist with the schizophrenic symptoms, or even occur only during the course of the illness without concurrent schizophrenic symptoms, the less convincing the definition of a schizoaffective psychosis appears. The less restrictive the related definition criteria are, the more diluted the concept becomes so that in the end any kind of depressive cosyndromality – simultaneous or sequential – can correspond to the diagnostic concept of a schizoaffective psychosis. It is therefore of relevance that DSM-III/IV defines a much more restrictive concept of schizoaffective psychoses than ICD-10.
Future role of a differentiated psychopathology
In the differentiation between schizophrenia with depressive/manic symptoms, depression or mania with psychotic symptoms and schizoaffective disorders, the psychopathological differentiation between mood-congruent and mood-incongruent psychotic symptoms has traditionally played an eminent role.100 Mood-incongruent psychotic symptoms were assumed by classical psychopathologists – such as Karl Jaspers or Kurt Schneider – to be ‘pathognomonic’ for schizophrenia (if an organic or medical condition is excluded), especially the so-called ‘first rank symptoms’. The DSM-IV, however, has involved mood-incongruent psychotic symptoms in mood disorders as well. But if mood-incongruent symptoms are seen to belong to mood disorders as well, then there is an increased risk of confusing traditional diagnostic entities such as pure mood disorders with schizoaffective disorders and to some extent with schizophrenia and schizophrenia disorders as well, with all the consequences, among others, for prognosis. Is the repeatedly described poor outcome of DSM-IV bipolar disorder possibly a consequence of this diagnostic shift? The discriminating power of mood-incongruent symptoms, and the boundaries between pure mood disorders and other psychotic disorders have been described in several studies.100,117,123–126
The Chicago 10-year follow-up study showed impressively that the differentiation between patients who in the acute phase had an affective disorder and either mood congruent or mood incongruent psychotic symptoms is of great prognostic value because those with mood-incongruent psychotic symptoms have a much poorer overall outcome.66 This was confirmed quite consistently by other recent studies without differentiating between mood-incongruent and mood-congruent psychotic symptoms.127–130
Altogether these findings indicate that especially mood-incongruent psychotic symptoms can be seen as an indicator of a poorer prognosis, a fact that should be better considered in modern classification systems and that especially questions the negative approach in DSM-IV. In their recent paper Marneros et al. came to the conclusion that the special characteristics of bipolar disorder with mood-incongruent psychotic symptoms can lead to similar conclusions as their polymorphism.131 With the term ‘polymorphism’ they describe the phenomenon according to which episodes other than mood episodes can also occur during the long-term course of bipolar I disorders, for example schizophreniform and ‘schizoaffective’ episodes (defined as concurrently fulfilling the criteria of both schizophreniform and mood episodes). It could theoretically be possible to argue that bipolar disorders with mood-incongruent psychotic symptoms have at least two comorbid disorders: schizophrenia and bipolar disorder. Marneros et al. noted that the construct of comorbidity cannot explain the fact that patients with mood-incongruent psychotic symptoms (such as bipolar patients with a polymorphic course) differ from patients with prototypic diseases, that is, schizophrenia or mood bipolar disorders without mood-incongruent psychotic symptoms, on various relevant levels (age at onset, family history, outcome etc.).131 They suggested that perhaps the answer can be found in the ‘antagonistic influence’ of both genetically determined or co-determined disorders, the result of which is a position of mood disorders with mood-incongruent psychotic symptoms in between the two prototypes.
The example of the delineation of schizoaffective disorder, as well as the example of the prognostic importance of the differentiation between mood-congruent/incongruent psychotic symptoms, underlines the fact that a differentiated psychopathological approach still should play a great role in modern psychiatry.59,100
We should be more careful about changing our psychiatric classification in such short intervals of 10–20 years. This always induces uncertainty among psychiatrists and patients and misunderstandings from outside the field. Should patients ‘ill for 40 years’ have their diagnosis changed two or three times only because of changes in the classification system? What does such a change mean for psychopharmacological treatment and drug licensing? What other impacts need to be anticipated?
For example, the licenses for psychotropic drugs have to be carefully considered. Are antipsychotics licensed for schizophrenia still the drug of choice, when schizophrenia is officially changed to a unitary psychosis that includes affective disorders? What about categories that might possibly not survive in DSM-V such as GAD, for which drug treatments were developed in the past? What about other new diagnostic entities that were traditionally classified according to other constructs? Will the new classification system lead to new demands for drug companies to perform new studies on their drugs already on the market for traditional entities?
A more pragmatic approach would be to implement only smaller changes58 and to suggest, among others, the use of a multi-axial approach as mandatory, to enable better descriptions of the heterogeneity. This multi-axial approach was suggested in ICD-10 and DSM-IV years ago, but was not fully introduced into everyday clinical practice for different reasons, especially not in the use of ICD-10. Such a multi-axial approach is without doubt a step forward, especially if the category ‘organic’ has been defined in a proper way, that is, in a dimensional and not a categorical way. Apparently, such a well-defined category dimension as ‘organic’ is lacking in our current diagnostics. The already well-established axes of global functioning and life stress are also very important.
Based on a more cautious and pragmatic approach, and associated with the growth in knowledge, in 20–50 years we might possibly be able to refine our diagnostic entities and to develop them in a more fruitful way. In the current situation there are possibly not sufficient empirical data to do this.
What would we like to expect from a cautious revision of our current diagnostic systems DSM-IV/ICD-10 in the best sense? Among other issues, the following should be addressed58: (i) improved refinement of diagnostic entities, among others improved definition of necessary and additional criteria, for example in the field of bipolar disorder; (ii) more detailed/precise characterization of subtypes, possibly using a dimensional psychometric approach; (iii) an improved approach concerning subthreshold disorders; (iv) more precise diagnosis of personality disorders based on a dimensional psychometric approach instead of a categorical conceptualization; (v) a better/full concordance between DSM-V and ICD-11; (vi) a multi-axial procedure, including current knowledge about cross-sectional and longitudinal psychopathological characteristics as well as neurobiological and psychosocial aspects and treatment response related to a diagnostic entity; and (vii) a more universalistic thinking, taking into account concepts from other regions of the world such as Asia, for example, in addition to the traditional European/North American predominance.
If nothing but the inclusion of an additional syndromatological approach could be reached, such an additional descriptive level to a categorical differentiation would be a fruitful improvement to our current diagnostic system. It must be clearly understood, however, that this means the mandatory application of comprehensive rating scales, which might be too demanding for everyday clinical practice, especially if we consider outpatient treatment. The vision for the future is to construct a psychiatric classification with regard to related neurobiological brain dysfunctions. A neuroanatomical/neuropathological basis might be at least of equal importance in this context as genetic findings. But clinical features/prototypes should also be considered. At the moment, the idea of constructing a new classification based only on neurobiological/neurogenetic parameters and not including clinical features does not seem promising.3