Department of Psychiatry, University Hospital, Zurich, Switzerland
Department of Psychiatry, University of Oxford, UK
Correspondence: Dr G. Milos, Department of Psychiatry,University Hospital,Culmannstr. 8, 8091 Zurich, Switzerland. Tel: +411 255 52 80; fax: +411 255 45 30; e-mail: gabriella.milos{at}usz.ch
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ABSTRACT |
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Aims To examine the course of the full range of clinical eating disorders.
Method A sample of 192 women with a current DSMIV eating disorder (55 with anorexia nervosa,108 with bulimia nervosa and 29 with eating disorder not otherwise specified) were assessed three timesover 30 months using a standardised interview.
Results Although the overarching category of eating disorder was relatively stable, the stability of the three specific eating disorder diagnoses waslow, with just a third of participants retaining their original diagnosis. This was due onlyin part to remission since the remission rate was low across all three diagnoses.
Conclusions There is considerable diagnostic flux within the eating disorders but a low overall remission rate. This suggests that underpinning their psychopathology may be common biological and psychological causal and maintaining processes.
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INTRODUCTION |
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METHOD |
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These participants were followed up 12 months and 30 months after the baseline evaluation. On each occasion they were invited for the follow-up interview in writing. Those who did not respond were contacted again in writing up to three times and repeated attempts were also made to establish contact by telephone. Ten participants who did not participate in a face-to-face interview at the second follow-up assessment were interviewed by telephone, a procedure that has been shown to be an acceptable alternative when diagnosing Axis I and II disorders (Rohde et al, 1997).
Almost three-quarters (74%) of the participants (n=205) were
reassessed 12 months after baseline, of whom 192 were also reassessed at 30
months (69% of the baseline sample). One participant died during the course of
the study. The proportion of participants who were reassessed did not differ
significantly between the three DSMIV eating disorder diagnostic
categories of anorexia nervosa, bulimia nervosa and eating disorder not
otherwise specified (EDNOS). However, non-participation was associated with
younger age (z=2.5, P=0.012) and a shorter duration of
eating disorder (z=3.3, P=0.001). Comparisons of
participants recruited through the different sources indicated that the groups
differed in age (KruskalWallis 2=31.2, d.f.=3,
P<0.001) and duration of eating disorder (
2=23.7,
d.f.=3, P<0.001) with those recruited from the in-patient unit
being the youngest (mean age 23.5 years, s.d.=5.8) and those with the shortest
eating disorder duration (mean 6.4 years, s.d.=4.7), followed by those
recruited as out-patients (mean age 27.1 years, s.d.=7.2; mean disorder
duration 10.4 years, s.d.=7.3). Participants recruited through self-help
groups (mean age 31.3 years, s.d.=7.3; mean disorder duration 14.7 years,
s.d.=8.6) and newspaper advertisements (mean age 30.8 years, s.d.=8.1; mean
disorder duration 13.1 years, s.d.=8.6) were older and had a longer duration
of eating disorder.
The 192 participants who took part in both follow-up assessments comprised 55 women with anorexia nervosa (mean body mass index (BMI) 15.3 kg/m2, s.d.=1.5), 108 with bulimia nervosa (mean BMI 21.7 kg/m2, s.d.=4.0) and 29 with EDNOS (mean BMI 22.4 kg/m2, s.d.=6.3). Twentynine (53%) of the anorexia nervosa cases were of the restrictive subtype and 26 (47%) were of the bingepurge subtype. Of the bulimia nervosa cases, 103 (95%) were of the purging subtype and 5 (5%) of the non-purging subtype. The characteristics of the EDNOS group were as follows: 1 (3%) met all the diagnostic features of anorexia nervosa except amenorrhoea; 8 (28%) met all the features of bulimia nervosa except the frequency or duration criteria. Other forms of EDNOS were present in 20 participants (69%) binge-eating disorder and mixed states (Fairburn & Bohn, 2005), in which the features of eating disorders were combined in a way that differed from anorexia nervosa and bulimia nervosa but were of clinical severity.
The mean age of the participants at study entry was 28.6 years (s.d.=7.9), with those with anorexia nervosa (mean age 26.6 years, s.d.=7.4) and bulimia nervosa (mean age 28.9 years, s.d.=8.1) being younger than those with EDNOS (mean age 31.6 years, s.d.=7.3); z=2.9, P=0.004 and z=2.2, P=0.032, respectively. The average age at onset of the eating disorder was 17.1 years (s.d.=4.1) and this did not vary between the diagnostic groups. The duration of eating disorder of the anorexia nervosa cases (mean 9.3 years, s.d.=7.2) was shorter than that of the bulimia nervosa cases (mean 11.7 years, s.d.=8.0) and the EDNOS cases (mean 14.4 years, s.d.=9.4); z=2.0, P=0.041 and z=2.4, P=0.015, respectively.
During the course of the study 88% of participants who completed the study (n=169) made contact with out-patient treatment providers and 34% (n=65) received in-patient treatment; 11% (n=21) received neither out-patient nor in-patient treatment.
Assessments
Eating disorders were diagnosed using the German version of the Structured
Clinical Interview for Axis I of the DSMIV (SCID;
Wittchen et al,
1997), conducted by four psychologists (interrater reliability
k=0.8) who had no contact with the participants other than the interviews for
the study. In line with DSMIV principles, a diagnosis of EDNOS was
given if eating disorder features were present and resulted in a clinical
degree of physical or psychosocial impairment yet the state did not fulfil
diagnostic criteria for anorexia nervosa or bulimia nervosa
(Fairburn & Bohn, 2005).
The European Cooperation in the Field of Scientific and Technical Research
COST Action B6 structured interview
(European Commission Directorate-General
Science, Research and Development, 2005) was used to assess
participants eating disorder features, history and secondary
impairment. At each follow-up assessment the procedure for making the eating
disorder diagnoses was the same as that used at the baseline. At all three
time points every eating disorder diagnosis was checked by a psychiatrist who
had extensive experience in evaluating patients with eating disorders (G.M.).
In addition, at each assessment an interview was used to identify any
treatment contact made in connection with the eating disorder, either before
or during the study.
Statistical analyses
The data were analysed using descriptive procedures and w2
tests. The variables age, duration of eating disorder and age at onset were
skewed and thus were analysed using non-parametric tests (KruskalWallis
and MannWhitney U tests). All tests were two-tailed and the
minimum alpha level was set at 5%.
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RESULTS |
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Remission from an eating disorder
There was considerable diagnostic instability. Taking the sample as a whole
(i.e. all those with a DSMIV eating disorder), only 55
participants retained the same diagnosis across all three assessment points,
representing 28.6% of the whole sample (or 32.9% when cases with a stable
remission at the two follow-up assessments were excluded). In part this
instability was due to remission, although overall the remission rate was low.
In all, just 20.8% (n=40) of participants were in remission at the
12-month follow-up (i.e. they had no clinical eating disorder), this figure
increasing to 31.3% (n=60) at the 30-month assessment. The remission
rates at both points varied significantly between the three diagnostic
categories (2=7.1, d.f.=2, P=0.029;
2=8.0, d.f.=2, P=0.019, respectively), with those
with EDNOS having the highest remission rate (31% and 52% at the first and
second follow-up points respectively), followed by those with bulimia nervosa
(24% and 31%) and anorexia nervosa (9% and 22%). However, remission was not a
stable state, either; of the 40 participants who were in remission at 12
months, less than two-thirds (n=25) were in remission at the second
follow-up. Just 13% (n=25) of the sample were in remission at both
assessment points.
Migration between eating disorder diagnoses
Although remission from an eating disorder was not common, migration
between the eating disorder diagnoses occurred in over half the cases. Thus,
taking the sample as a whole, but excluding those who no longer had an eating
disorder at one or both follow-up points, 62 (53%) crossed over from one
eating disorder diagnosis to another. This diagnostic migration was evident in
all three diagnostic groups. Thus, of the 55 individuals with an initial
diagnosis of anorexia nervosa, only 31 (56%) retained the diagnosis at 12
months and just 27 (49%) still had the diagnosis at 30 months. Twenty-three
participants with an initial diagnosis of anorexia nervosa (48%) retained this
diagnosis at both reassessments. Change in eating disorder diagnosis was even
more evident among those with bulimia nervosa. Of the 108 participants with
bulimia nervosa at baseline, only 55 (51%) had this diagnosis at the first
reassessment and just 40 (37%) had it at the second. Only 29 (27%) of the
women with an initial bulimia nervosa diagnosis retained this diagnosis at
both reassessments. Diagnostic instability also characterised those with
EDNOS. Of the 29 participants with EDNOS at baseline, just 8 (28%) still had
the diagnosis at 12 months and 9 (31%) at 30 months, and only 3 (10%) had
EDNOS at both reassessments. The rate of retention of an anorexia nervosa
diagnosis was similar for the two subtypes of anorexia nervosa (restrictive
subtype: first follow-up n=17, 57%, second follow-up n=14,
48%; bingepurge subtype: first follow-up n=14, 54%, second
follow-up n=13, 50%). With regard to crossover between eating
disorder diagnoses, marginally more anorexia nervosa cases changed to bulimia
nervosa (20%, n=11) at either or both follow-up points than vice
versa (9%, n=10); 2=3.7, d.f.=1, P=0.053.
Overall, 37% (n=60) of the participants with a baseline diagnosis of
anorexia nervosa or bulimia nervosa were given a diagnosis of EDNOS at either
or both follow-up points, a rate that did not differ between the two original
diagnoses.
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Illness duration and diagnostic stability
Table 2 shows the duration
of eating disorder at study entry for each diagnosis broken down by diagnosis
at 30-month follow-up. For those who had anorexia nervosa, eating disorder
duration was associated with retention of the diagnosis at 30 months
(2=9.3, d.f.=3, P=0.026); specifically, women who
retained their diagnosis had a significantly longer eating disorder history at
study entry than those who were in remission at 30 months (z=3.0,
P=0.002). Similarly, women with a baseline diagnosis of anorexia
nervosa who showed a stable remission (no eating disorder at both
reassessments) had a shorter history (mean 1.8 years, s.d.=1.5) at study entry
than those who did not experience a remission at either or both time points
(mean 9.9 years, s.d.=7.2; z=2.8, P=0.002) and than those
who retained an anorexia diagnosis at both follow-up points (mean 8.6 years,
s.d.=7.2; z=2.6, P=0.007). Those with bulimia nervosa or
EDNOS showed no association between eating disorder duration and either change
in diagnosis or stable remission. Also, no association emerged between age at
onset of the eating disorder and change in diagnostic status, either in the
whole sample or within any of the three diagnostic categories.
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Treatment contact
Participants therapeutic experiences were classified into
out-patient treatment contact (psychotherapist, psychologist, psychiatrist or
general practitioner) or in-patient treatment contact (psychiatric or
psychotherapeutic in-patient unit or day clinic, or a general hospital). At
baseline almost all participants had made some contact with out-patient
treatment providers because of their eating disorder (97%, n=186).
Almost half (49%, n=94) had received in-patient treatment. Only six
participants (3%) had received no treatment at all. During the course of the
study 88% of participants (n=169) made contact with out-patient
treatment providers and 34% (n=65) received in-patient treatment; 11%
(n=21) received no treatment. Treatment contact (out-patient
v. no out-patient treatment, in-patient treatment v. no
in-patient treatment) before study entry or during the study was not
associated with stable remission (i.e. no eating disorder diagnosis at both
follow-up assessments) either in the whole sample or within the diagnostic
subgroups.
Purging behaviour
Participants diagnoses at all three assessment points were
classified as either purging or non-purging, using the DSMIV threshold
frequency of purging behaviour (vomiting or use of laxatives) occurring at
least twice a week. When no eating disorder was diagnosed at follow-up, the
state was classed as non-purging. At baseline, 58 (30.2%) diagnoses were
classified as non-purging and 134 (69.8%) as purging. After excluding the 25
individuals who experienced a stable remission (i.e. no eating disorder
diagnosis at both follow-up assessments), analyses showed that 53.7%
(n=65) of 121 participants with a baseline purging eating disorder
received at some point (first and/or second follow-up) a non-purging
non-purging diagnosis, whereas of 46 participants with a non-purging eating
disorder at baseline 17.4% (n=8) subsequently received a purging
diagnosis (2=17.9, d.f.=1, P50.001). When considering
the rates of stable remission, participants with a non-purging type of
disorder at baseline had a significantly higher recovery rate (21%,
n=12) than participants with a purging type of disorder (10%, n=13;
2=4.3, d.f.=1, P=0.038).
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DISCUSSION |
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Diagnostic instability
There were three main findings. First, diagnostic stability was low. Just a
third of participants retained their original diagnosis over the 30 months,
when cases with a stable remission were excluded. Second, this was only in
part due to remission, since the remission rate was low across all three
diagnostic categories and stable remission was unusual (13%). This is of note
because this was a naturalistic follow-up study, with 89% of participants
having contact with treatment providers. The finding is consistent with the
widely held view that eating disorders are self-perpetuating and difficult to
treat (Fairburn & Harrison,
2003), a view that is further bolstered by the fact that the
remissions observed were often temporary, with a subsequent return of the
eating disorder. The third finding is perhaps the most striking. It is that
although the overarching diagnosis of eating disorder was
relatively stable, there was considerable flux between the three specific
eating disorder diagnoses. Indeed, change in diagnosis occurred in over half
the cases. All three eating disorder diagnoses showed this tendency. Anorexia
nervosa was the most stable diagnosis, followed by bulimia nervosa and then
EDNOS. Interestingly, prior course only predicted outcome in anorexia nervosa,
where length of history was positively associated with greater diagnostic
stability.
There is much published research on the outcome of anorexia nervosa and bulimia nervosa, but few studies have investigated the course of EDNOS or examined it as a possible outcome of anorexia nervosa or bulimia nervosa (Fairburn & Bohn, 2005). This is important because recent studies suggest that EDNOS is comparable in severity to the two main eating disorder diagnoses and is often preceded by them (Fairburn & Bohn, 2005). The studies on the outcome of bulimia nervosa have produced findings similar to ours. For example, Bulik et al (1997) reported that 54% of patients with anorexia nervosa developed bulimia nervosa at some point during a mean follow-up interval of 15.5 years, with the median duration between onset of anorexia nervosa and conversion to bulimia nervosa of 2 years. Sullivan et al (1998) reported that in patients who do not recover from anorexia nervosa, crossover to bulimia nervosa was a frequent occurrence. In addition, the results of our study confirmed the clinical impression that during the course of an eating disorder, crossover from bulimia nervosa to anorexia nervosa is also possible.
In line with our findings, the data from a 5-year follow-up study also indicated that there were considerable fluctuations between the eating disorder diagnoses, as well as differences between the categories in stability and remission rates, with anorexia nervosa having the highest stability and lowest remission rates compared with bulimia nervosa and EDNOS (Ben-Tovim et al, 2001). However, this study assessed outcome only once and the diagnoses were not made using a standardised instrument.
Our results also showed that, after excluding participants with a stable remission, changes between eating disorder categories of the restrictive and the bingepurge type were frequent. In line with other studies (Eckert et al, 1995; Fichter & Quadflieg, 1997, 1999; Steinhausen, 2002), we found that participants with a non-purging non-purging eating disorder had a higher recovery rate than those with bingepurge behaviour.
Eating disorders or eating disorder?
The shared and distinctive psychopathology of anorexia nervosa, bulimia
nervosa and EDNOS (Fairburn & Harrison,
2003; Fairburn & Bohn,
2005) and the frequent movement of patients between the diagnoses,
together with the fact that the average age at onset did not differ between
them, strengthens the view that these disorders have so much in common that
they might be best viewed as a single entity. They also highlight certain
limitations of the current diagnostic scheme: for example, minor changes in
weight or eating behaviour can result in a person receiving an entirely
different DSMIV eating disorder diagnosis. Similarities and differences
between the eating disorder diagnoses and the classification of eating
disorders have been points of discussion for decades. Two recent developments
are evident. One is to highlight the similarities between the eating disorder
categories rather than focus on their differences. This is the basis of the
transdiagnostic view of the eating disorders
(Fairburn et al,
2003). The other trend is to examine the classification of eating
disorders from the perspective of predictive validity (e.g.
Strober et al, 1999;
Bulik et al, 2000;
Stice & Fairburn, 2003;
Keel et al, 2004). The findings of this study certainly suggest that the diagnostic migration
that occurs between the eating disorders needs to be taken into account in
thinking about their classification
(Fairburn & Bohn,
2005).
Limitations and strengths
Certain limitations of the study are of note. Cases of EDNOS were
underrepresented in comparison with their proportion in out-patient eating
disorder clinics (Fairburn & Bohn,
2005). Most of the participants had some contact with treatment
providers and it is conceivable that treatment might have contributed in part
to the diagnostic changes observed. Withdrawal from the study was associated
with younger age and shorter duration of eating disorder possibly good
prognostic features, thereby contributing to the low remission rate. Another
possible limitation is the relatively short duration of follow-up (30 months),
but this was not inappropriate since our aim was to study diagnostic
fluctuation rather than long-term outcome. Further studies of the course of
the full range of eating disorders are clearly needed, ideally with treatment
controlled.
Strengths of the study include the broad patient sample, which included participants with anorexia nervosa, bulimia nervosa and EDNOS, and the use of standard diagnostic procedures with clinical severity thresholds.
Implications
Our findings have implications beyond nosology: the clinical reality of
shared but distinctive clinical features across the eating disorders, together
with diagnostic flux between them, signifies that underpinning the
psychopathology of anorexia nervosa, bulimia nervosa and EDNOS are likely to
be common biological (Uher et al,
2004) and psychological causal and maintaining processes
(Fairburn et al,
2003). The implication of this is that transdiagnostic approaches
to research on the psychopathology and treatment of these disorders, and their
neurobiology, would be of merit.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Received for publication December 22, 2004. Revision received February 20, 2005. Accepted for publication March 8, 2005.
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