Staging anorexia nervosa: conceptualizing illness severity

Review Article

Staging anorexia nervosa: conceptualizingillness severity

Sarah Maguire,1 Daniel le Grange,2 Lois Surgenor,3 Peta Marks,4 Hubert Lacey5 and Stephen Touyz1

1School of Psychology, 4Department ofPsychological Medicine, University ofSydney, Sydney, Australia, 2Departmentof Psychiatry, The University of Chicago,Chicago, Illinois, USA, 3Department ofPsychological Medicine, University ofOtago, Christchurch, New Zealand; and5School of Medicine, University ofLondon, London, UK

Corresponding author: Ms SarahMaguire, Level 2 Building 92, RoyalPrince Alfred Hospital, NSW 2050,Australia. Email:[email protected]

Received 26 September 2007; accepted10 December 2007

Abstract

In recent years, there has beenincreasing attention to the conceptu-alization of anorexia nervosa (AN)and its diagnostic criteria. Whilevarying levels of severity within theillness category of AN have long beenappreciated, neither a precise defini-tion of severity nor an empiricalexamination of severity in AN hasbeen undertaken. The aim of thisarticle is to review the current state ofknowledge on illness severity and topropose a theoretical model for thedefinition and conceptualization ofseverity in AN. AN is associated withsignificant medical morbidity which

is related to the ‘severity’ of presenta-tion on such markers as body massindex, eating and purging behaviours.The development of a functionalstaging system, based on symptomseverity, is indicated for reasonssimilar to those cited by the cancerlobby. Improving case managementand making appropriate treatmentrecommendations have been theprimary purpose of staging in otherfields, and might also apply to AN.Such a standardized staging systemcould potentially ease communica-tion between treatment settings, andincrease the specificity and compara-bility of research findings in the fieldof AN.

Key words: anorexia nervosa, diagnosis, eating disorders, illnessstaging, severity.

INTRODUCTION

Anorexia nervosa (AN) is a psychiatric disorder withsignificant levels of chronicity1 and medical mor-bidity,2 as well as one of the highest reported mor-tality rates.3,4 The term ‘severe’ is often used indescriptions of AN. Two recent studies have gone sofar as to directly examine the entity of ‘severe AN’ byinvestigating the genetics5 and epidemiology6 of thisspecific group of patients. Despite frequent refer-ence to and investigation of severity in AN, anempirical examination of the construct of severity inAN, its measurement and operationalization, is yetto be conducted.

Illness staging has been a strategy successfullyutilized in a number of medical disorders, mostnotably cancer, to conceptualize illness severity, soas to better provide treatments tailored to clinicalpresentation, to bring a focus to early interventionand to prevent the progression of illness from lessto more severe forms. Recently, as the AmericanPsychiatric Association commences deliberations

about DSM-V, it has been suggested that clinicalstaging be considered as a strategy to better diag-nose the psychiatric disorders.7

In this conceptual article, we review the existingknowledge on severity of AN, suggest a justificationfor its formal conceptualization and propose astaging model for its measurement.

Clinical description of AN: psychological,behavioural and physical symptoms along theseverity continuum

Anorexia nervosa expresses itself along three inter-related axes: psychological, behavioural and physi-cal. The symptoms on each of the axes vary in kind,extent and intensity. The primary distortion is psy-chological and arguably the intensity of this distor-tion determines the severity of the behavioural andphysical disturbances.

Characterized psychologically by an intensedrive for thinness, AN develops into an extremefear of weight gain, normal weight and ‘fatness’.

Early Intervention in Psychiatry 2008; 2: 3–10 doi:10.1111/j.1751-7893.2007.00049.x

© 2008 The AuthorsJournal compilation © 2008 Blackwell Publishing Asia Pty Ltd

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mailto:[email protected]

Accompanying body image disturbance, whichrenders the individual unable to accept the impera-tive for weight gain, means the sufferer with ANoften sees or experiences themselves as ‘fat’ despitebeing underweight. Since the 1970s, these two psy-chological components have been conceptualizedas causal in the pathological behaviours that ensuein AN,8–10 and have consequently served as diagnos-tic criteria for this disorder. Ancillary psychologicalfeatures present in many cases, but are not neces-sary to meet DSM-IV diagnostic criteria, e.g. perfec-tionism, obsessionality, depression, an egosyntonicattachment to the illness and poor or ambivalentmotivation for recovery.

Behaviourally, the AN phenotype expresses thecore psychological drive for weight reductionthrough a varying set of behaviours, includingextreme dietary restriction often accompanied bycompensatory behaviours (self-induced vomiting,laxative abuse and excessive exercise/activity).Those affected by AN can also engage in more gen-erally disordered eating, including bingeing.

Relationships between the core psychological andbehavioural features of AN and the consequentphysical sequelae of the illness have been wellestablished lending themselves to a continuum ofseverity model. An abundance of evidence can befound to demonstrate this interrelatedness in sever-ity in AN. For instance, it is well accepted that theintensity of dietary restriction and compensatorybehaviours determine the extent of weight loss inAN. Loss of menses is strongly correlated with ahighly restrictive eating pattern, even at healthyweights.11,12 Electrolyte imbalance is both a result offluid and food restriction and purging behav-iours.11,13 Hypophosphataemia can be induced byexcessive exercise14 or binge eating.15 Food and fluidrestriction can result in cardiac dysfunction,11 whilechronic purging and ipecac use can lead to irrevers-ible cardiac pathology.16

The relationship between these core symptomscan become more complex over time as the achieve-ment of weight loss and the anxiolytic effects ofpurging, along with the effects induced by the star-vation response, take place. The illness behavioursbecome both self-reinforcing and reinforce the psy-chological distortions of the illness,17 causing theperson with AN to engage in increasingly extrememethods of weight reduction.

The constellation of psychological, behaviouraland physical symptoms varies greatly within theillness spectrum, causing considerable heterogene-ity in the presentation of AN.18 Symptoms vary inboth kind and intensity, and this variation in diseasepresentations has been conceptualized as occuring

on a continuum. Recent taxometric analysis hasdemonstrated support for this hypothesis.19 Not-withstanding, the optimal way to conceptualize andaccount for differences in symptoms is an area thatremains to be explored.

Staging AN: a model of severity

It is not widely known that even the earliest descrip-tions of AN made reference to the concept of stagesof severity within the illness. Lasegue,20 creditedwith providing the first published accounts of AN,describes a gradual descent into the illness, distin-guishing three distinct ‘phases’ in its progression.The first phase is marked by an ‘uneasiness and full-ness’ after eating, with consequent reductions infood intake. The second is characterized by severerestriction, increased activity levels and an ‘intellec-tual perversion’ resulting in a complete denial of theillness, before finally ‘the disease enters upon itsthird stage’ involving extreme emaciation, laboriousexercise and a ‘general debility’.

Researchers since then have often made referenceto discreet stages of illness and most of these refer-ences have made an implicit assumption aboutseverity. For example, some have referred to anacute stage versus a re-feeding stage, or a chronicstage and recovered stage of the illness.21 Some havedescribed a progression through stages with a‘chronic stage’ of AN receiving most attention.17 Anumber of studies have investigated the variousphysical and psychological concomitants of whatresearchers describe as ‘chronic AN’.22–24 Generallypresumed to be the worst manifestation of the dis-order and with the poorest prognosis, the criteria forclassification within the ‘chronic stage’, or any otherstage, have not been investigated. Consequently,many investigators utilize an illness duration ofgreater than 5–7 years to denote chronicity.25

Another approach to staging of AN, but one thatdoes not make assumptions about the severityof illness, has been proposed.26–28 Similar to thecourse-like staging utilized in schizophrenia, thisstrategy involves the division of AN patients into thefollowing categories: ill/episode; partial remission/recovery; sustained recovery; and relapse, based onthe extent to which persons meet the core diagnos-tic criteria of AN. Although helpful, course-likestages are often somewhat self-evident labels of thediagnostic status of the illness. Further, other thanthe stages of ill and not ill (episode and remission/recovery), Kordy et al.28 were unable to demonstratestability or predictive utility of the other stages.

The purpose of this article is to stimulate debatewhich we hope might result in a more sophisticated

Staging anorexia nervosa

4 © 2008 The AuthorsJournal compilation © 2008 Blackwell Publishing Asia Pty Ltd

understanding about which symptoms in AN, atwhich degree of intensity, result in which outcome.If course-like staging is a longitudinal examinationof the illness, the present examination will be one ofillness extent. The imperative for staging is ulti-mately utilitarian in maximizing understanding ofthe varying presentations within the illness, provid-ing maximal information on the best treatment, andin better predicting outcome. As early attempts atcourse-like staging are yet to yield such information,the present proposal will explore the potential forstaging based upon severity.

History of disease staging

Staging refers to the determination or classificationof distinct phases or periods in the course of adisease or pathological process; that is, the determi-nation of the specific extent of a disease process inan individual person.29 Staging has long been usedas a strategy to operationalize illness severity. Theearliest attempts at staging were reported in 1748when diphtheria was categorized according toseverity, where corresponding differences in prog-nosis were determined for the various stages. Sincethen, a number of medical afflictions have beenstaged, including heart disease and burns. Perhapsthe most widely recognized and documentedstaging model is that used for cancer. The TNMsystem (tumor, node, metastasis) divides cancersinto five stages from least (stage 0) to most severe(stage IV) based on the anatomical extent of thecancer on three axes; the physical extent of thetumor (T), the involvement at the lymph nodes (N)and distant spread or metastasis (M). The purposeof the TNM classification when developed in the1980s was outlined as fourfold:30 (i) to select appro-priate standard treatments; (ii) to evaluate theresults of new treatments; (iii) to acquire data in anorderly fashion for statistical analysis of end results;and (iv) to estimate prognosis.

All of these four goals have been significantlyadvanced since the TNM system was agreed upon in1987.31 The cancer model is continually evolving,with research underway to incorporate new indica-tors of prognosis such as genetic markers and spe-cific treatment factors.32 It is also recognized that themaintenance of a standardized system for staging,according to anatomic extent of the illness in pre-serving the TNM fundamentals, is necessary forongoing research in the field.33

Several mental illnesses have also been staged,although these have a shorter history. Dementia,first staged in the previous century, is an illnesswhose progression follows a fairly uniform course,

which makes it suitable for staging. Alcohol use hasbeen staged according to severity with differentprognoses indicated based on stage of illness.Schizophrenia uses a course-like staging separatingillness groups into acute, remitting or chronicstages. Observed similarities between chronic ANand chronic schizophrenia34 suggest that a similarcourse-like staging approach may be useful in AN. Ithas been observed that AN in its chronic form canpresent with similar negative symptoms thatbecome pronounced in chronic schizophrenia, e.g.blunted affect, social withdrawal and odd ideas.However, the relationship between positive andnegative symptoms used in schizophrenia to de-lineate the chronic stage is not as clear in AN. Evenin its chronic form, the ‘positive’ symptoms of theillness – drive for thinness, body image disturbance– can be acutely present, and it is common forpersons with chronic AN to continue to be high-functioning and to lack most or all of these so-callednegative symptoms.

The existing staging literature reveals severalthemes of relevance to the field of AN. When prog-nosis is uniformly poor, staging is regarded asunhelpful.31 When outcome is highly varied, as is thecase for AN, then the examination of disease factorsthat may affect prognosis becomes important. Thestaging of a disease can result in a renaissance intreatment development and more effective treat-ment delivery with consequent improvements indisease outcome and the development of treatmentguidelines for each stage of the illness.35,36 Althoughprognostic indicators are a desired result of staging,the primary purpose of staging, at least in medicaldisorders, is to guide treatment selection and casemanagement.32,33 With the exception perhaps of thediagnostic criteria for AN, few subjects receive asmuch attention in the literature as the dearth ofeffective treatments for this illness and the need forreinvigoration in this area.18,37,38 The interindividualdifferences within AN, and lack of a meaningful wayto classify and examine outcome in AN, are poten-tial barriers to the development of treatments foreating disorders. Collectively, these argumentsemphasize the importance of a thorough examina-tion of the spectrum of illness in AN and possiblecategories therein.

What is severity in AN?

Although a handful of studies have purported toinvestigate variably ‘severe’ subgroups within AN,there has been no empirical examination to derive aworking definition of severity. This is surprisinggiven that AN is a disorder with a high mortality

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rate,39 and one that poses significant treatment chal-lenges.40 This may be in part due to the difficultiesinherent in any exploration of severity: differencesin illness presentation between individuals,40,41 thetendency for significant numbers with this disorderto remain hidden from examination,42 the failure todistinguish reliable predictors of outcome3 and thedifferences in theoretical approaches to this disor-der across countries. Conversely, there are severalreasons why severity becomes an importantconcept to explore in AN. These include to betterunderstand the commonalities and divergences inpresentation, to better design and more systemati-cally institute treatment, and to both improve andbetter predict outcome.

Traditional usage of the concept of illness severitysuggests a twofold conceptualization. First, thatseverity refers to the extent to which the key markersof the disease are present within the individual, andthat severity should imply some harm to, or pooroutcome for, the individual. Currently, the term‘severe’ is applied in AN for either/or of the abovereasons. That is, persons where the key markers ofthe illness are present to a great extent are describedas ‘severe’, but this is performed in the absence ofknowledge about prognosis. And vice versa, thosewho ultimately have a poor outcome are posthu-mously ascribed the term ‘severe’ independent oftheir previous symptomatic status. In illnesses wherethese two aspects are known to enjoy a close relation-ship, the definition of severity is simplified. One suchillness is dementia where the presence or absence ofsymptoms is highly predictive of prognosis, becausethe course (although not the duration) of the diseaseis quite uniform.43 In diseases with a fluctuatingcourse or where the relationship between the extentof the disease within the individual and outcome isunknown, unclear or has been underexamined, anunderstanding of severity is more difficult. In thecase of melanoma, unlike the majority of cancers,the extent of the cancer as defined by the TNMsystem (tumor, node, metastasis) has often proven tobe a poor predictor of prognosis.44 Similarly for AN,the relationship between symptom severity andprognosis is unclear.1 However, this lack of under-standing regarding the relationship between symp-toms and prognosis is at least in part a result of a lackof rigorous research. Outcome studies in AN are fewand although the symptoms of the illness have beenwell documented, these studies only have examinedthe presence or absence of a limited number ofsymptoms, rendering conclusions on overall severityin the illness premature.

Until the relationship between the symptoms ofAN and prognosis becomes clearer, rendering a

full understanding of severity in AN, discussingsymptoms and aspects of prognosis separately maybe helpful.

Symptomatic severity in AN

The majority of references to ‘severe AN’ in the sci-entific literature base such a description on thepresence, to a specified extent, of one or more of thesymptoms of the illness. The most common of theseare body mass index (BMI) and menses.25 Both BMIand menses have been conceptualized along a con-tinuum of severity; a lower BMI and an absence ofmenses denote a more ‘severe’ symptomatic presen-tation. Although a division of questionable scientificvalidity, the DSM employs these two features of theillness in its rudimentary division of the spectrum ofAN presentations into full-syndromal AN (a bodymass below 85% of normal and lack of menses) andsubthreshold cases which are classed in the diag-nostic category of Eating Disorder-Not OtherwiseSpecified (ED-NOS). This leads to speculation thatthese ED-NOS cases are a less ‘severe’ form of AN.45

Investigations into the differences between ANand ED-NOS cases along behavioural and psycho-logical dimensions have yielded some informationrelevant to an understanding of symptomatic sever-ity in AN. Other than the diagnostic distinctions onBMI and menstrual status, a number of studies havefailed to find any differences in ‘severity’ of othercore features between AN and ED-NOS cases.Bunnell et al.46 examined both groups on a range ofbehavioural and psychological axes, includingeating behaviours, drive for thinness and bodyimage dissatisfaction/disturbance, and found nodifferences between the two groups. Van Der Hamet al.41 found very little difference between AN casesand ED-NOS cases on core eating disorder psycho-pathology, but found some differences on psycho-social measures, with AN performing more poorlyon these measures. Ricca et al.47 examined AN andED-NOS cases on general psychopathology andeating disorder-specific psychopathology as mea-sured by the Eating Disorder Examination48 andfound no differences between groups. They con-clude that ED-NOS cases with an ‘AN-like’ presenta-tion should be absorbed into the AN criteria. Crowet al.49 compared these two groups on eating disor-der and general psychopathology, depression, self-esteem and social adjustment and were unable todistinguish full from partial AN. This study did findone psychological variable that distinguished thesetwo groups – preoccupation with eating disorderthoughts.



In general, these studies were limited in theirability to detect differences between AN andED-NOS as the questionnaires utilized were notvalidated to distinguish severity per se. Moreover,research into differences between ED-NOS and ANis complicated by the diagnostic confusion sur-rounding ED-NOS. It is unclear whether thesestudies utilized only those ED-NOS cases that fall onthe AN spectrum or if these findings also included alarger mix of ED-NOS cases, for example bulimic orother atypical cases. ED-NOS can serve as a diag-nostic way-station for persons remitting from AN, oron their way towards meeting AN diagnostic crite-ria. Therefore, it is not always clear at what stage ofillness cases were examined for these studies.

A further imperative for defining the ‘severity’ ofAN according to such symptomatic features as lowBMI, drive for thinness and extreme eating behav-iours is in part due to the fact that although theprognostic or nosological status these featuresconfer is unclear, they have been associated with thepresence of some of the more serious physicalsequelae in AN. Irrespective of prognosis, the accu-rate assessment of these physical sequelae and their‘severity’ becomes important in preventing medicalmorbidity in AN. If untreated, these physicalsequalae can lead to irreversible bone loss, repro-ductive complications and loss in cognitive func-tioning, even in cases of a full-recovery from AN. Asa result, investigators tend to refer to presentationsof AN with cardiac abnormalities, osteoporosis andcognitive impairment as more ‘severe’. A prospectiveexamination of the overall prognosis indicated bythese symptoms is lacking. Although symptoms inAN are typically conceptualized to vary along a con-tinuum of extent or ‘severity’, a full understanding ofwhich symptoms at which particular level indicatesubgroups of the disorder remains absent.

Prognosis in AN

Steinhausen,1,50 in his seminal reviews of outcome inAN in the 20th century, concluded that predictingprognosis for this disorder with the current level ofknowledge is a ‘hazardous endeavour’. Despite con-flicting evidence, he was able to isolate severalsymptoms of AN consistently associated with apoorer outcome. Most clearly, vomiting, bingeing,purgative abuse and obsessive-compulsive symp-toms were unfavourable prognostic features, alongwith longer duration of illness. Steinhausen notedthat there were a myriad of methodological weak-nesses in the studies he reviewed, including variablesample sizes, durations of follow-up, varying defini-tions of outcome and assessment measures, and the

confounding effect of treatment. This led him toconclude that, based on these findings, delineatingrules about individual prognosis in a patient suffer-ing from AN was precluded. One of his primaryobservations was that few of the studies utilized themore powerful prospective design. Two prospectivestudies51,52 have established that low BMI is consis-tently associated with a poorer outcome over time.In these studies, purging behaviours, abnormalpathology results, increased general psychopathol-ogy and social disturbances also predicted a poorercourse of illness. It should be noted that studies ofpersons with an early onset of AN have not consis-tently replicated the finding concerning lowerBMI,53–55 which suggests that there may be a rela-tionship between age at onset and weight loss indetermining severity in AN.

Research by Hebebrand et al.56,57 suggest thatalthough the relationship between weight loss andoutcome may not be linear, partitioning patientsinto groups dependent on weight loss may provemore fruitful. His group failed to find a significantrelationship between weight loss and outcomeuntil the cohort was partitioned into such groups,and then found that the lowest weight group(BMI < 13 kg m-2) conferred a significantlyincreased risk for the worst outcomes – chronicillness and death. This finding suggests that dividingpatients into subgroups based upon symptomaticseverity may hold prognostic value.

The above studies and many other follow-upanalyses, used cohorts of persons with AN treatedwithin eating disorder treatment settings, oftenreserved for the most ‘severe’ cases, and hence mayhave provided a skewed understanding of prognos-tic indicators for the AN spectrum. A longitudinalexamination of the outcome of AN utilizing cohortsfrom broad community samples is yet to be pub-lished. One cross-sectional study comparing theoutcome of AN and ED-NOS within the communityreported similar levels of mortality in both diagnos-tic categories.58 This study did not specificallyexamine the AN subtype of ED-NOS, and was cross-sectional in nature. As ED-NOS can often functionas an early or late stage of AN as the individual isentering or exiting from the illness, it is difficult toascertain whether ED-NOS cases that carried a highmortality risk would be more accurately describedas AN cases at various stages of recovery.

Limited evidence suggests that certain symptomsin AN may indicate a poorer chance at recoveryfrom the illness (e.g. low weight, purgative behav-iours, obsessive-compulsive features), but the exist-ing studies have multiple limitations. Along withthose already mentioned, most studies have

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employed a narrow definition of outcome. The mea-sures used to examine symptomatic severity havebeen limited, as have those to assess outcome. Mosthave only assessed full syndrome diagnoses of AN,despite agreement that the illness spectrum isbroader.18,47 None have looked at the intercorrela-tions and interactions of prognostic indicators inAN. It may well be that a group of variables, ratherthan any single variable alone, can better predictoutcome in AN.

The role of illness course in conceptualizingseverity

Centrally relevant to the conceptualization of sever-ity is the role of illness duration. It has been hypoth-esized that the best predictor of outcome in AN isthe duration of illness. In any illness where the stan-dardized mortality rate observes an almost linearrelationship with time, as in AN (mortality rates at10 years fall at about 10%,3 and at 20 years about20%2,52), illness course or duration becomes animportant variable in the understanding of illnessseverity. Inversely, outcome studies also report anincreased tendency towards recovery with a longerduration of follow-up – at 5 years approximately50% have fully recovered which increases to about75% at 12 years.3 This suggests that the relationshipbetween duration and severity, at least in terms ofultimate prognosis, is a complex one. On anotherlevel, the understanding of the effect of duration ofillness (i.e. illness course) on eventual outcome is oflimited utility. It is a somewhat circular argument tostate that the duration of the illness will be the bestpredictor of ultimate illness outcome; a long dura-tion of illness could after all be regarded as itself apoor outcome. It can be argued that a fuller under-standing of illness severity attempts to delineatewhich features of the illness, and other markers,best predict duration of illness and ultimateoutcome.

Why the need for a staging model?

The staging of illness is not a new approach. In fact,it could be argued that there is already a measure ofstaging in the diagnostic criteria for eating disorderswith ED-NOS being applied to ‘milder’ cases of ANand full diagnosis to more severe cases, thereforenegating the need to further complicate the system.However, the diagnostic system, in its currentformat, is confusing in that ED-NOS is seen as toobroad and heterogeneous a category which limits itsutility.59 Consequently, ED-NOS does not necessar-ily enhance case identification or the development

of appropriate treatments. One potential advantageof the staging model we propose is that it might havethe capacity to accommodate all presentations ofAN within the same diagnostic category, but withsubgroups delineated based on symptomatic andprognostic factors.

Di Clemente and Prochaska’s60 stages of changemodel has also been applied to the eating disorders,most effectively to AN. The stages of precontempla-tion through to action and relapse have been suc-cessfully mapped to AN and instruments developedto assess preparedness for change in this disorder.These, it could be argued, are adequate stages fora disorder like AN where motivational stance ispivotal to presentation. Although a useful psycho-logical tool, an individual’s stage of change is onlyone marker of illness presentation existing within avariety of different disease presentations. An indi-vidual can be at severe medical risk as a conse-quence of AN, yet still present in a highly motivatedstage of change. Similarly, a person can be in partialremission yet present as resistant of any furtherchange. These two cases are likely to have differingprognoses. The model of illness staging proposed inthis manuscript takes account of the psychologicalpresentation of the individual, including motiva-tional stance, but in the larger context of total symp-tomatic severity. It encompasses psychological,behavioural and physical symptoms to arrive at astage to be assessed for its prognostic utility.

In contrast to its potential benefits, the possibilitythat a staging model might over-pathologize analready stigmatized psychiatric disorder should alsobe considered. If successful, and stages of illnessdenoting prognosis are delineated, it is possible thatpersons at either end of the spectrum may be dis-criminated against. Persons with Stage 1 AN beingdenied the same access to treatment as more severecases, and persons with Stage 4 illness potentiallyrelegated to the ‘too hard to treat’ basket. Hence, thedevelopment of any staging model needs to be per-formed with due consideration to its potential usesand misuses.

DISCUSSION

Anorexia nervosa is not a new illness; first describedin 1873, it has been the subject of consistent empiri-cal examination at least since the 1950s. Despiteover five decades of research, we are no closer to afull understanding of the etiology or prognosis ofthis disorder or closer to the development of effec-tive treatment.38,40 When knowledge is elusive, thereoften is a return to basic principles. That is, no fewer



than 15 articles in the last 10 years have addressedthe diagnostic conceptualization of AN, some ofwhich have identified the heterogeneity of this dis-order as well as the ongoing challenge to arrive atappropriate subclassification as major barriers to abetter understanding.40 An examination of AN alongthe continuum of severity, and subtyping in theform of stages thereafter, bears consideration for anumber of reasons.

Anorexia nervosa varies in terms of severity, bothin terms of symptom presentation and diseaseoutcome. The key symptoms of AN have for themost part been conceptualized as existing on a con-tinuum of severity. Although examination of thecontinuum has largely focused on the distinctionbetween cases and non-cases, neglecting within-illness variation, long-term follow-up studies havebeen unable to delineate consistent single predic-tors of outcome. Only one study has grouped ANsufferers according to a purported marker of illnessseverity, i.e. BMI.56,57 Although these authors foundno significant relationship between weight loss andoutcome when considering these variables as con-tinuous, the grouping of subjects resulted in thefinding that those with the poorest outcomes weremost frequently from the group with the most‘severe’ weight loss. No study has considered group-ing individuals with AN according to a number ofmarkers of severity to establish whether outcomecan be better predicted.

Apart from the key prognostic role that staging ANcould potentially serve, the development of a func-tional staging system, based on symptom severity, isindicated for reasons similar to those cited by thecancer lobby. AN is associated with significantmedical morbidity, which if untreated can lead toirreversible impairment. Such morbidity is relatedto the ‘severity’ of presentation on such markers asBMI, eating and purging behaviours. Efficacioustreatment for AN remains elusive and although ithas been suggested that varying levels of care maybe helpful,61 assigning persons to treatment basedon symptomatic presentation is hazardous giventhe lack of any empirically based means to do so. Toimprove case management and make more appro-priate treatment recommendations have been theprimary purpose of staging in other fields, and thesearguably apply to AN. The development of a stan-dardized staging system would ease communica-tion between treatment settings, and couldpotentially increase the specificity and comparabil-ity of research findings in the field of AN. To this end,we are developing and testing a staging instrumentthat separates AN spectrum into subcategoriesbased on symptomatic severity, i.e. the Clinician

Administered Staging Instrument for AnorexiaNervosa (CASIAN).62 We are currently conductingvalidation and reliability studies to demonstrate theutility and predictive validity of the CASIAN.

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Staging anorexia nervosa: conceptualizing illness severity