Jablensky's paper provides a rich developmental history of the conceptual approach to classification in psychiatry that has immediate application for the current revisions of the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (ICD). By identifying the conceptual differences between disease, disorder, syndrome and symptoms, he identifies the limitations and challenges in the century-old attempt in all of medicine to move towards a disease concept for each organ system. The disease concept that links aetiology and pathophysiology with an observable syndrome that can guide treatments and even cures is the aspirational goal for all of medicine (Regier, Reference Regier2003). However, there are few diagnostic entities in psychiatry in which all the links are known in a causal chain to predict clinical course and response to treatments – based on an understanding of aetiology or pathophysiology. Hence, we are left with the somewhat amorphous concept of a mental ‘disorder’, which postulates some underlying deficit in developmental, psychological or biological function that is pathological and outside the range of normal. Although some risk factors of temperament, personality, familial aggregation, molecular genetics, trauma, stress and other environmental exposures are known that increase the probability for development of these conditions, there is no exact combination of these that lead to the common final pathway of most mental disorders. Since there is a more limited set of cognitive thought, emotional and behavioural responses available to the human brain than there are potential causes of psychopathology, we are left with a set of ‘final common pathway’ mental disorders that are inherently heterogeneous. What makes the ‘disease concept’ for mental disorders even more difficult to conceptualize is the ability of the human brain to respond to pathogenic insults with a remarkable array of neuroplastic adaptations to maintain a homoeostatic level of functioning.
Despite the best efforts of scientists over the past century to find single causal agents for specific mental disorders, we have a relatively small number of infectious (e.g., central nervous system syphilis), nutritional (pellagra), genetic (Huntington's Disease), anatomical cell death (Alzheimer's Disease) and toxic (lead poisoning) conditions where aetiological agents are clearly identified along with a typical clinical course – for which some have curative treatments and most do not. For most of the mental disorders, we now know that there are literally thousands of genetic variations that constitute vulnerabilities for mental disorders when interacting with environmental exposures in the context of resilient homoeostatic adaptations to produce what we can identify as psychopathological ‘disorder’ entities. Hence, within our current mental disorder groups, this bewildering array of causal pathways results in recognizable syndromes, which are inherently heterogeneous. However, we base our clinical judgments on these disorder groups to predict likely clinical course and responsiveness to available psychotherapy, pharmacologic and somatic treatments. Although Jablensky suggests that we are operating more at a syndrome level than a disease level, the same social, psychological and philosophical reasons that Jaspers (Reference Jaspers, Hoenig and Hamilton1963) identified for using the ‘disease entity fiction’ also apply to psychiatry's use of the ‘disorder entity fiction’ – it indicates the path for fruitful research and supplies a valid point of orientation for empirical investigations and treatment selection.
Given the current status of classification in psychiatry, the syndrome-based disorder concept has been remarkably productive in producing empirically based treatment strategies for groups of patients that differ in substantial ways. Apart from the identification of niacin to treat pellagra and penicillin to treat CNS syphilis, there has also been the discovery of dopamine blocking agents (phenothiazines) to treat psychotic disorders, serotonin and norepinephrine reuptake inhibitors to treat depression, benzodiazepines to treat anxiety and insomnia disorders, opioid-blocking agents to treat addictive disorders, anti-epileptic agents to treat manic disorders and a range of other psychotropic agents that alter the usual clinical course of mental disorders. In addition, psychotherapeutic interventions such as cognitive behavioural treatments have been shown to alter the natural clinical course of mood, anxiety, addictive, sexual, cognitive and personality disorders. Nonetheless, we are far from understanding the reason why some individuals within these heterogeneous disorder groups respond dramatically to available interventions and others persist with severe and persistent mental disorders. It is this heterogeneity that continues to challenge members of DSM and ICD revision work groups to identify principles for setting boundaries around specific mental disorders and links between disorder groups.
Jablensky traces the history of how previous individuals and groups have responded to this challenge beginning in the 19th century with Alzheimer, Kraepelin and Bleuler. Alzheimer's discovery of the anatomical distortions in autopsied brains of patients with dementia led Kraepelin to hope for similar anatomical explanations and reproducible correlates for psychotic illnesses. However, these were not found and the only reliable basis for separating psychotic illnesses was the difference in clinical course between what he identified as dementia praecox and manic-depressive psychosis. The former was seen as following a chronic deteriorating course, much like the dementia of Alzheimer's disease, and the other an intermittent exacerbation and stabilization course with a possible recovery. However, even Kraepelin (Reference Kraepelin, Hirsch and Shepherd1920) recognized in his later years that there was heterogeneity in those he initially identified with one or the other disorders. His pipe organ analogy of each disorder being more like a registry on the pipe organ like the distinct trumpet, krumhorn or reed stops that can be blended into mixtures provided a remarkably apt analogy to our current understanding of the multifactorial nature of multiple gene environmental interactions – as different stops are pulled that can blend these contributing factors into an almost infinite combination of sounds that can be produced. Although there are distinct central tendencies that can be recognized as autism, schizophrenia, bipolar disorder, major depression, anxiety disorders and addictive disorders, the potential for mixtures of the constituent symptoms of these ‘registers’ gives rise to the heterogeneity that we experience with our classification and groupings.
It is most likely that a more dimensional classification that facilitates an accurate description of the symptom combinations that exist in nature will help us develop better syndromes than those we have with the current mental disorder definitions. It is interesting that the cognitive deficits in schizophrenia are not specifically noted as diagnostic criteria even though the dementia praecox of Kraepelin focused specifically on this component. Instead, the perceptual distortions of hallucinations and delusions, the thought disorder, and the negative behavioural symptoms receive precedence. The National Institute of Mental Health's MATRICS Project (Green et al. Reference Green, Nuechterlein, Kern, Baade, Fenton, Gold, Keefe, Mesholam-Gately, Seidman, Stover and Marder2008) was an attempt to provide a more dimensional approach to the cognitive symptoms and the US Food and Drug Administration has even indicated a willingness to provide an indication for medications that can specifically improve the cognitive dimension of schizophrenia. It is also possible that dimensional measures from neuroimaging studies of brain regions (e.g., dorsal medial prefrontal cortex for major depression; Holtzheimer & Mayberg, Reference Holtzheimer and Mayberg2010) and connecting neuronal tracts (e.g., autism; Wolff et al. Reference Wolff, Gu, Gerig, Elison, Styner, Gouttard, Botteron, Dager, Dawson, Estes, Evans, Hazlett, Kostopoulos, McKinstry, Paterson, Schultz, Zwaigenbaum and Piven2012) will contribute additional syndrome and disorder components as we seek to understand abnormalities of the pathophysiology underlying the symptomatic expression that we can currently observe.
As our technology and conceptual approaches to classifying mental disorders continues to evolve, we need to be careful that we do not continue to reify strict categorical boundaries between mental disorders. The validators that we have used for these disorders to date, such as family and population genetics, clinical course, treatment response and laboratory measures have failed to confirm these boundaries even though broad groupings have been helpful for directing clinical care. Our challenge for the future will be to establish a framework that is responsive to a more dimensional approach. The merger of a categorical diagnostic approach that identifies central tendencies with a dimensional approach that clearly describes patient presentations has been identified as a goal since Kraepelin (Reference Kraepelin, Hirsch and Shepherd1920). Jablensky also noted the observation of Hempel (Reference Hempel and Zubin1961) that ‘although most sciences start with a categorical classification of their subject matter, they often replace this with dimensions as more accurate measurements become possible’. Although complete replacement of categorical diagnoses is not the goal of DSM-5, accommodating a framework for the integration of more dimensional psychological, biological and behavioural measures is essential to advancing clinical practice and research in this field.
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Jablensky's paper provides a rich developmental history of the conceptual approach to classification in psychiatry that has immediate application for the current revisions of the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (ICD). By identifying the conceptual differences between disease, disorder, syndrome and symptoms, he identifies the limitations and challenges in the century-old attempt in all of medicine to move towards a disease concept for each organ system. The disease concept that links aetiology and pathophysiology with an observable syndrome that can guide treatments and even cures is the aspirational goal for all of medicine (Regier, Reference Regier2003). However, there are few diagnostic entities in psychiatry in which all the links are known in a causal chain to predict clinical course and response to treatments – based on an understanding of aetiology or pathophysiology. Hence, we are left with the somewhat amorphous concept of a mental ‘disorder’, which postulates some underlying deficit in developmental, psychological or biological function that is pathological and outside the range of normal. Although some risk factors of temperament, personality, familial aggregation, molecular genetics, trauma, stress and other environmental exposures are known that increase the probability for development of these conditions, there is no exact combination of these that lead to the common final pathway of most mental disorders. Since there is a more limited set of cognitive thought, emotional and behavioural responses available to the human brain than there are potential causes of psychopathology, we are left with a set of ‘final common pathway’ mental disorders that are inherently heterogeneous. What makes the ‘disease concept’ for mental disorders even more difficult to conceptualize is the ability of the human brain to respond to pathogenic insults with a remarkable array of neuroplastic adaptations to maintain a homoeostatic level of functioning.
Despite the best efforts of scientists over the past century to find single causal agents for specific mental disorders, we have a relatively small number of infectious (e.g., central nervous system syphilis), nutritional (pellagra), genetic (Huntington's Disease), anatomical cell death (Alzheimer's Disease) and toxic (lead poisoning) conditions where aetiological agents are clearly identified along with a typical clinical course – for which some have curative treatments and most do not. For most of the mental disorders, we now know that there are literally thousands of genetic variations that constitute vulnerabilities for mental disorders when interacting with environmental exposures in the context of resilient homoeostatic adaptations to produce what we can identify as psychopathological ‘disorder’ entities. Hence, within our current mental disorder groups, this bewildering array of causal pathways results in recognizable syndromes, which are inherently heterogeneous. However, we base our clinical judgments on these disorder groups to predict likely clinical course and responsiveness to available psychotherapy, pharmacologic and somatic treatments. Although Jablensky suggests that we are operating more at a syndrome level than a disease level, the same social, psychological and philosophical reasons that Jaspers (Reference Jaspers, Hoenig and Hamilton1963) identified for using the ‘disease entity fiction’ also apply to psychiatry's use of the ‘disorder entity fiction’ – it indicates the path for fruitful research and supplies a valid point of orientation for empirical investigations and treatment selection.
Given the current status of classification in psychiatry, the syndrome-based disorder concept has been remarkably productive in producing empirically based treatment strategies for groups of patients that differ in substantial ways. Apart from the identification of niacin to treat pellagra and penicillin to treat CNS syphilis, there has also been the discovery of dopamine blocking agents (phenothiazines) to treat psychotic disorders, serotonin and norepinephrine reuptake inhibitors to treat depression, benzodiazepines to treat anxiety and insomnia disorders, opioid-blocking agents to treat addictive disorders, anti-epileptic agents to treat manic disorders and a range of other psychotropic agents that alter the usual clinical course of mental disorders. In addition, psychotherapeutic interventions such as cognitive behavioural treatments have been shown to alter the natural clinical course of mood, anxiety, addictive, sexual, cognitive and personality disorders. Nonetheless, we are far from understanding the reason why some individuals within these heterogeneous disorder groups respond dramatically to available interventions and others persist with severe and persistent mental disorders. It is this heterogeneity that continues to challenge members of DSM and ICD revision work groups to identify principles for setting boundaries around specific mental disorders and links between disorder groups.
Jablensky traces the history of how previous individuals and groups have responded to this challenge beginning in the 19th century with Alzheimer, Kraepelin and Bleuler. Alzheimer's discovery of the anatomical distortions in autopsied brains of patients with dementia led Kraepelin to hope for similar anatomical explanations and reproducible correlates for psychotic illnesses. However, these were not found and the only reliable basis for separating psychotic illnesses was the difference in clinical course between what he identified as dementia praecox and manic-depressive psychosis. The former was seen as following a chronic deteriorating course, much like the dementia of Alzheimer's disease, and the other an intermittent exacerbation and stabilization course with a possible recovery. However, even Kraepelin (Reference Kraepelin, Hirsch and Shepherd1920) recognized in his later years that there was heterogeneity in those he initially identified with one or the other disorders. His pipe organ analogy of each disorder being more like a registry on the pipe organ like the distinct trumpet, krumhorn or reed stops that can be blended into mixtures provided a remarkably apt analogy to our current understanding of the multifactorial nature of multiple gene environmental interactions – as different stops are pulled that can blend these contributing factors into an almost infinite combination of sounds that can be produced. Although there are distinct central tendencies that can be recognized as autism, schizophrenia, bipolar disorder, major depression, anxiety disorders and addictive disorders, the potential for mixtures of the constituent symptoms of these ‘registers’ gives rise to the heterogeneity that we experience with our classification and groupings.
It is most likely that a more dimensional classification that facilitates an accurate description of the symptom combinations that exist in nature will help us develop better syndromes than those we have with the current mental disorder definitions. It is interesting that the cognitive deficits in schizophrenia are not specifically noted as diagnostic criteria even though the dementia praecox of Kraepelin focused specifically on this component. Instead, the perceptual distortions of hallucinations and delusions, the thought disorder, and the negative behavioural symptoms receive precedence. The National Institute of Mental Health's MATRICS Project (Green et al. Reference Green, Nuechterlein, Kern, Baade, Fenton, Gold, Keefe, Mesholam-Gately, Seidman, Stover and Marder2008) was an attempt to provide a more dimensional approach to the cognitive symptoms and the US Food and Drug Administration has even indicated a willingness to provide an indication for medications that can specifically improve the cognitive dimension of schizophrenia. It is also possible that dimensional measures from neuroimaging studies of brain regions (e.g., dorsal medial prefrontal cortex for major depression; Holtzheimer & Mayberg, Reference Holtzheimer and Mayberg2010) and connecting neuronal tracts (e.g., autism; Wolff et al. Reference Wolff, Gu, Gerig, Elison, Styner, Gouttard, Botteron, Dager, Dawson, Estes, Evans, Hazlett, Kostopoulos, McKinstry, Paterson, Schultz, Zwaigenbaum and Piven2012) will contribute additional syndrome and disorder components as we seek to understand abnormalities of the pathophysiology underlying the symptomatic expression that we can currently observe.
As our technology and conceptual approaches to classifying mental disorders continues to evolve, we need to be careful that we do not continue to reify strict categorical boundaries between mental disorders. The validators that we have used for these disorders to date, such as family and population genetics, clinical course, treatment response and laboratory measures have failed to confirm these boundaries even though broad groupings have been helpful for directing clinical care. Our challenge for the future will be to establish a framework that is responsive to a more dimensional approach. The merger of a categorical diagnostic approach that identifies central tendencies with a dimensional approach that clearly describes patient presentations has been identified as a goal since Kraepelin (Reference Kraepelin, Hirsch and Shepherd1920). Jablensky also noted the observation of Hempel (Reference Hempel and Zubin1961) that ‘although most sciences start with a categorical classification of their subject matter, they often replace this with dimensions as more accurate measurements become possible’. Although complete replacement of categorical diagnoses is not the goal of DSM-5, accommodating a framework for the integration of more dimensional psychological, biological and behavioural measures is essential to advancing clinical practice and research in this field.