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The ‘continuum of psychosis’: scientifically unproven and clinically impractical

  • Stephen M. Lawrie (a1), Jeremy Hall (a1), Andrew M. McIntosh (a1), David G. C. Owens (a1) and Eve C. Johnstone (a1)...

The limitations of current diagnostic categories are well recognised but their rationale, advantages and utility are often ignored. The scientific support for a ‘continuum of psychosis' is limited, and the examination of whether categories, a continuum or more than one continua, and alternatives such as subtypes or hybrid models, best account for the distributions of symptoms in populations has simply not been done. There is a lack of discussion, let alone consensus, about the critical aspects of psychosis to measure, the best ways to quantify those and how these would be applied in clinical practice. Systematic studies are needed to evaluate which of a range of plausible approaches to the classification of psychosis is most useful before change could be justified.

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Corresponding author
Stephen M. Lawrie, Division of Psychiatry, University of Edinburgh, Kennedy Tower, Royal Edinburgh Hospital, Edinburgh EH10 5HF, UK. Email:
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The ‘continuum of psychosis’: scientifically unproven and clinically impractical

  • Stephen M. Lawrie (a1), Jeremy Hall (a1), Andrew M. McIntosh (a1), David G. C. Owens (a1) and Eve C. Johnstone (a1)...
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Re: The classification system must be usable in healthcare systems all over the world

Stephen M Lawrie, Professor of Psychiatry
09 February 2011

Authors reply

We thank Dr’s Gordon and Shoesmith for their interest in our editorial, their complimentary remarks and their considered responses to what we said.

Dr Gordon repeats our call to avoid prematurely abandoning categoriesor dimensions, and highlights the lack of known diagnostic biomarkers for psychosis, either as a whole or for current sub-types. Tandon et al (1) didn’t really consider this, quite reasonably, as their review focuses on what is known about the aetiology and pathogenesis of schizophrenia. As we have clarified in a forthcoming review (2), the lack of known biomarkers for psychosis (whether as categories or continua) is at least partly because the right sort of studies to find them have only rarely been done and reported in this light. The relevant populations need to bestudied and then the results analysed according to the principles of clinical epidemiology (or evidence-based medicine), to extract the potential clinical significance for individuals of statistically significant abnormalities evident in groups of patients. Thus, for example, if one wished to identify specific diagnostic markers of schizophrenia which have clinical utility, a (preferably large) representative population of people in their first episode would need to be assembled, and predictive values and/or likelihood ratios calculated for the value of potential markers of schizophrenia as opposed to say bipolar disorder. Despite the paucity of studies, there are already a fewwell replicated large differences between patients with schizophrenia and healthy controls, which may also distinguish them from those with bipolardisorder (2). Not all of these require high-tech investigations. Simpleclinical measures of neurodevelopmental aberration, such as neurological soft signs, and even historical measures such as early social difficulties, are common in people who go on to develop schizophrenia but may not be in those with bipolar disorder. These already influence clinical decision making but in an informal and rather haphazard fashion. The optimal method of eliciting and using such information needs further investigation as outlined above and in our review in press.

Dr Shoesmith is absolutely right to remind us that any resource intensive diagnostic procedure is going to be much less practical in less well developed health services. This is of course an immediate and quite possibly fatal problem for any system requiring multiple ratings on continua and could be even more so if, for example, magnetic resonance imaging of the brain/mind turns out to be diagnostically valuable – as we suspect it might (2). In the long run, whatever turns out to be the bestconceptual approach to psychosis for the maximal benefit of patients, and whether or not this has to be pioneered in leading clinical research centres, the process of formalizing our diagnostic and therapeutic judgements will bring a much-needed and long-overdue re-engagement of psychiatry with the rest of medicine.

SM Lawrie, J Hall, AM McIntosh, DGC Owens, EC JohnstoneDivision of Psychiatry, Royal Edinburgh Hospital, Morningside, Edinburgh EH10 5HF

1.Tandon, R; Keshavan, MS; Nasrallah; H. A. Schizophrenia, Just the facts: what we know in 2008. Part 1: Overview. Schizophr Res 2008; 100: 4-19.

2.Lawrie SM, Olabi B, Hall J, McIntosh AM. Do we have any solid evidence of clinical utility about the pathophysiology of schizophrenia? World Psychiatry in press.
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The classification system must be usable in healthcare systems all over the world.

Wendy D. Shoesmith, Senior Lecturer in Psychiatry
22 December 2010

Lawrey and colleagues urged us not to prematurely reject the current categorical classification system [1]. I wish to add to the argument that a categorical system is more likely to be useful. More than 80% of mental illness occurs in middle and low income countries [2]. Much of the world’s mental illness is seen in overstretched clinics, by practitioners who treat up to 100 patients a day and often have had no training in psychiatry since medical or nursing school. Conducting the rating scales necessary for a dimensional system may be possible in developed countries, but would be difficult or impossible anywhere else. The categorical classification system can be used quickly, by someone with relatively little training. There is also the problem of translating and validating the rating scales into hundreds of languages. Most published research currently uses the same categorical system, which means that it is useful to doctors all over the world. If the research were to refer only to a dimensional system, then it would not be useful in settings where it is impossible to do the rating scales. The categorical system gives more people access to evidence based treatment than any dimensional system would. A classification system that is going to be used all over the world needs to be simple and robust across healthcare systems, language and culture and this is just as important as how closely it resembles the truth.

1. Lawrie SM, Hall J, McIntosh a M, Owens DGC, Johnstone EC. The “continuum of psychosis”: scientifically unproven and clinically impractical. The British Journal of Psychiatry. 2010;197(6):423-425. Available at:

2. World Health Organization. Disease and injury regional estimates for 2004. Available at:

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Conflict of interest: None Declared

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Physics to the Rescue

Saad F Ghalib, consultant in old age psychiatry
17 December 2010

The authors are justified in their attempt to cuation us against a premature rejection of the well established categorical diagnostic system.

considering the lack of specific bio-markers, contrary to the authorsclaim, research in psychiatry is at best epidemiological and at worst a misleading statistical haze.

the present situation is reminiscent of the late 1920s where a serious debate erupted over the nature of light, and whether it should be regarded as made of particles or waves. The view adopted thenafter is neither and both, depending on the question being asked. In a bold move, Niels Bohr proposed that mutually exclusive concepts are still necessary to be able to give a coherent presentation of nature( complementarity ).

Dimensions and categories,may initially seem mutually exclusive. However, at a basic level the two concepts are connected in more ways thanmeet the eye,and are both necessary for better understanding of psychiatric disorders.A Bayesian approach is one way of reconciling the apparently two mutually exclusive concepts. That is a top-down approach(categorical),without loosing sight of a bottom-up approach(dimensions). Therefore, probabilities for both methodologies will be taken into account, but more importantly linked in one coherent framework.Statistically,attempts to plot the probability of detecting a certain psychotic symptom whenever schizophrenia is identified, is a whole different ball game to plotting the probability of ascertaining the validity of schizophrenia concept when the same symptom is detected in a cohort.Bayes statistics can help in model selection,evaluating evidence correctlywhen two or more competing models(dimensions vs categories)are being proposed. The comparison does not depend on the parameters used by each model.Instead,it considers the probability of the model considering all possible parameter values.It is just not feasible to expect sensible answers on categories if the set up is primarily designed to measure dimensions. One should not expect studies on antipsychotics to validate the concept of schizophrenia when those same medicines are being utilized in the treatment of bipolar disorder and psychotic depression.By the same token, one can never be certain that having a genetic susceptibility to paranoid thinking( no matter on which end of spectrum it falls) is good enough confirmation thatthe concept of schizophrenia is valid and pathophysiologically robust. However, what genetic research can do is to give us some clues on how the enviroment shapes the onset,presentation, and prognosis of psychiatric conditions.

declaration of interest; none
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"Bathwater and the baby"

Peter J. Gordon, Consultant in Old Age Psychiatry Place of work
13 December 2010

This is a timely and welcome editorial from Stephen M. Lawrie et al.1I see this debate two ways: as a doctor needing ?order? to help ease suffering I agree that it is better, for the time being, to keep existing diagnostic categories of disorder however imperfect they may be. As a patient I of course want care, but I also want to be understood. Many of us are now considering that too much of life is being branded disorder:here none of us diminishes suffering, but we do look for better ways of explaining. Certain scientists may hate it ? but our lives do have narrative. I think we underestimate mankind if we say that we cannot accept symptom based descriptions of suffering. I hope I am not wrong to suggest that most of the treatments that today used to improve mental health are not ?disease specific? but rather act upon either mood, thought, or both.

Nevertheless the cry for a spectrum approach to psychosis I would agree is premature and does not fit with my experience of so many troubledlives encountered. Peter Tyrer our Editor is correct to raise the potential problems of premature abandonment; both clinical and pragmatic.2However there remains a need to reconsider the neo-Kraepelinian model, if nothing more than to bring greater alignment with the technology that Lawrie et al now hope will be to our greater mental good. As the classification system is at present, it is my belief that neurobiological research cannot fully address complexity. My own view is that we have rather given too much attention to what Steven Rose has termed ?neurogenetic determinism? rather than applying biological research to life 3 (baby and the bath water, however dirty).

I would contest the presentation of the neurobiology literature as presented here by Lawrie in the opening paragraph of the Editorial, andquote: ?based on highly replicable neurobiological differences.? This cites the paper ?Schizophrenia, ?just the facts?; what we know? by Tandon,Keshavan and Nasrallah.4 I have read this paper several times, but found,for all the studies and indeed all the words, neither one simple biomarkerof any utility nor indeed anything even approaching specificity. Perhaps we should ask why this may be? Could it be that categories, clinically practicable, and needed for now, do not match the complex epigenesis of psychosis?

In concluding I would suggest that we do not forget history. Maxwell-Clerk was bold enough to stop looking for matter and to consider the energy fields that now govern our lives and indeed the technology which has been to our collective good. Do we need another Maxwell-Clerk moment, scientifically brilliant, religion free, willing to see matters as simple as possible, but not simpler?

I have no such moment to offer. But brilliant Edinburgh folk like Lawrie have that tradition and they perhaps raise the chances that such scientific inspiration can help us once again.

Dr Peter J. Gordon1st December 2010

1. Lawrie, S; Jeremy, H; McIntosh, A. M; Owens, D. G. C; Johnstone,E.C: The ?continuum of psychosis?: scientifically unproven and clinically impractical. The British Journal of Psychiatry (2010) 197: 423-425.

2. Tyrer, P: From The Editor?s Desk. The British Journal of Psychiatry (2010) 197: 423-425.

3. Rose, S.P.R. The biology of the future and the future of biology Perspectives in Biology and Medicine - Volume 44, Number 4, Autumn 2001, pp. 473-484

4. Tandon, R; Keshavan, MS; Nasrallah; H. A. Schizophrenia, ?Just the facts?: what we know in 2008. Part 1: Overview. Schizophr Res 2008; 100; 4 ?19.
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Patients' needs come first

Ilias Partsenidis, MRCPsych (currently on a career break)
08 December 2010

This editorial has successfully raised an important definition/classification problem. However, I would like to point out that it might be counterproductive to debate whether a “continuum of psychosis” or the present categorical classification is more appropriate, especially in view of the vast amount of further research needed. I think a better approach might be to try and calibrate the symptoms of psychosis as accurately as possible to a quality of life measure e.g. a modified Global Assessment of Functioning scale as this would be more relevant to clinical practice. It is more important to attend to each patient’s individual practical needs than merely treat the “schizophrenia” or the “severe end of the psychosis continuum”.

Furthermore, the authors state that “individual symptoms are less reliably elicited than a multidimensional diagnosis, they vary in severity over time and may differ in different environmental contexts”. I think that a detailed description of specific symptoms is by definition more reliably elicited than a multidimensional diagnosis. Of course a detailed description of specific symptoms will be more long-winded than a diagnosis but it will correspond more accurately to the patients’ actual experience.

Declaration of interest: None.
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