Psychological Medicine, 1990, 20, 671-680 Printed in Great Britain

Prevalence of three bulimia syndromes in the general population JOHN A. BUSHNELL, 1 J. ELISABETH WELLS, ANDREW R. HORNBLOW, MARK A. OAKLEY-BROWNE AND PETER JOYCE From the Departments of Community Health and General Practice, and Psychological Medicine, Christchurch School of Medicine, University of Otago, Christchurch, New Zealand

Prevalence of bulimia was estimated from a cross-sectional general population survey of 1498 adults, using the Diagnostic Interview Schedule (DIS) administered by trained lay interviewers. Lifetime prevalence of the DSM-III syndrome in adults aged 18-64 was 1 0 % and this was concentrated in young women: in women aged 18-44 lifetime prevalence was 2-6%, and 1 0 % currently had the disorder. Based on clinicians' reinterviews of random respondents and identified and marginal cases, the prevalence of current disorder using criteria for draft DSM-III-R bulimia was 0-5%, for DSM-III it was 0-2%, and for Russell's Criteria bulimia nervosa 0 0 % . A strong cohort effect was found, with higher lifetime prevalence among younger women, which is consistent with a growing incidence of the disorder among young women in recent years. Although elements of the syndromes were so common as to suggest that dysfunctional attitudes to eating and disturbed behaviour surrounding eating are widespread, there was little evidence of the bulimia syndrome having become an epidemic on the scale suggested by early reports.

SYNOPSIS

INTRODUCTION Limitations of prevalence studies Since the formulation of criteria for the definition of bulimia nervosa (Russell, 1979), and bulimia (American Psychiatric Association, 1980), the eating disorder has been the subject of a flurry of survey activity (Stangler & Printz, 1980; Johnson et al. 1982; Fairburn & Cooper, 1982, 1984; Pope et al. 1984). Early studies which attempted to establish the prevalence of the disorder obtained very high rates of bulimia (e.g. Halmi et al. 1981), fuelling media reports of an 'epidemic' of the disorder of huge proportions. Many attempts to estimate prevalence have been constrained by methodological inadequacies. There has been a proliferation of questionnaires designed to assess the syndrome, many of which have not appraised all the features of the DSM-III syndrome and have uncertain specificity (Halmi et al. 1981; Johnson 'Address for correspondence: John Bushnell, Department of Community Health and General Practice, Christchurch School of Medicine, University of Otago, PO Box 4345, Christchurch, New Zealand.

et al. 1984; Nevo, 1984; Ben-Tovim, 1989). With the exception of a few studies (Pope et al. 1985; Pyle et al. 1983, 1986), prevalence studies have generally not shown clearly whether prevalence rates are for lifetime occurrence or current disorder. Several studies have confused incidence with prevalence (Pyle et al. 1983; Johnson et al. 1984; Gray & Ford, 1985). In a disorder in which guilt and secrecy are common features (Fairburn & Cooper, 1982; Abraham & Beumont, 1982), heavy reliance has been placed on self-report questionnaires. The use of interviews to explore the clinical relevance of symptoms has seldom been undertaken, and where it has, the adequacy of self-report questionnaires alone has been questioned (Pyle et al. 1986; Schotte & Stunkard, 1987). Furthermore, the choice of population to be sampled, the narrow age-range studied, and the method of selection (Pyle et al. 1983; Crowther et al. 1985; Hart & Ollendick, 1986; Zuckerman era/. 1986) and low participation rates (Crowther et al. 1985; Pope et al. 1985; Hart & Ollendick, 1986; Drenowski et al. 1988) limit the generalizability of many findings.

671

672

J. A. Bushnell and others

Varying diagnostic criteria Confusion resulting from differences in methodology has been compounded by concurrent use of three differing sets of diagnostic criteria. Because of incomplete matching of these criteria, it has been difficult to compare the results of studies which have used one definition with studies using another. In 1980 the American Psychiatric Association's (APA) DSM-III criteria identified five criteria for the disorder: recurrent binge eating; having three of five specified disordered eating behaviours; awareness that eating pattern is abnormal and fear of not being able to stop eating voluntarily; depressed mood and self-deprecating thoughts following a binge; and exclusion of the syndrome in the presence of anorexia nervosa. The 1985 draft revision of APA criteria (DSM-IIIR) (American Psychiatric Association, 1985) became available as the field work for this study was beginning. Renamed bulimia nervosa, this syndrome eliminated three elements from the list of five disordered eating behaviours, and did not require awareness that the eating pattern is abnormal, or that self deprecating or depressed thoughts follow bingeing. The revised criteria required at least two binge-eating episodes per week for a minimum of three months. In the UK in 1979, Russell had stipulated three necessary conditions for bulimia nervosa: powerful and intractable urges to overeat; compensation for bingeing by vomiting or use of purgatives; and a morbid fear of becoming fat. Direct comparisons of all these criteria have not been made, but DSM-III and draft DSM-IIIR criteria applied to a sample of college students indicated that the revised criteria defined a more restricted diagnosis (Schotte & Stunkard, 1987). The present study This study set out to establish the current, six month and lifetime prevalence of DSM-III bulimia in a probability sample of adults in the community. It was part of a larger survey of the prevalence of psychiatric disorder and its relation to use of health services (Wells et al. 1989). A standardized lay-interviewer administered questionnaire was followed by clinician re-interviews of all definite and possible cases of DSM-III bulimia, among which Russell's Criteria and draft DSM-IIIR bulimia nervosa were also

assessed. Secondary aims relating to examining co-morbidity of other psychiatric disorders with bulimia will be addressed in a separate publication. METHOD Sampling strategy A probability sample of 1498 adults aged 18-64 years was drawn from the urban area of Christchurch, New Zealand, a city of 300000 residents of whom approximately 93 % are of European descent. The method of the study was based on the National Institute of Mental Health Epidemiologic Catchment Area Program (Regier et al. 1984), and has been described in detail elsewhere (Wells et al. 1989). The sampling strategy involved systematic selection of 250 Primary Sampling Units (PSUs) from the census tracts of the entire Christchurch urban area. From these PSUs, dwellings were systematically selected and within each dwelling, Kish selection (Kish, 1965) was used to identify one respondent. Because of the special interest of the research team in affective and eating disorders, younger women were oversampled by selecting only women aged 18-44 years in every third household approached. First interview Respondents were interviewed by lay interviewers trained to use Version 3A of the Diagnostic Interview Schedule (DIS) (Robins et al. 1981). The DIS is a structured interview designed for administration by trained lay interviewers which yields information about the presence of symptoms, permitting DSM-III diagnoses (DIS/DSM-NI disorders) to be made. All the interviewers were female. Their average age was 34 years. Participation of respondents in the survey was negotiated on the understanding that the interview explored issues to do with mental health, and use and satisfaction with health services. No specific mention was made of eating disorders. The bulimia section occurred about halfway through the 90 minute interview, and took respondents with symptoms of bulimia approximately 15 minutes to complete. Second interview Respondents with disorders of interest selected on the basis of their first interview DIS responses,

Prevalence of three bulimia syndromes

were re-interviewed within a month by a male clinician (M. O.-B. or J. B.). Cases of definite or marginal bulimia, alcohol disorder or depression were re-interviewed, along with a group of respondents selected at random, so the clinician, who was blind to the initial interview findings, did not know whether any re-interview was a case or not. The clinician readministered the bulimia, depression, mania, alcohol and drug abuse sections of the DIS and ensured completion of a number of self-report questionnaires including the Eating Disorders Inventory (Garner et al. 1983 b), then carried out a further semistructured exploration of symptoms. Using a checklist of the criteria for the disorder, the clinicians were free to ask any question to determine if those criteria were met. The criteria included those for DSM-III bulimia, the 1986 draft DSM-IIIR bulimia nervosa and Russell's 1979 bulimia nervosa. The comprehensiveness of this assessment was compromised by two deficiencies. For DSM-IIIR bulimia nervosa it was not ascertained whether bingeing at the rate of twice a week had occurred for three months duration. Difficulty operationalizing Russell's criteria 'morbid fear of becoming fat' led to the adoption of a solution similar to that of Fairburn & Cooper (1982). Since the Eating Disorder Inventory (EDI) items relate to the current time period, the complete syndrome was assessed for current disorder only. Because there are limited data permitting EDI scores to be related directly to 'caseness' of bulimia using standard diagnostic nomenclature, (Welch & Hall, in the press) the EDI data have not been used to identify cases and are not reported within this paper. An index of severity of the disorder was constructed using the number of symptoms of DSM-III bulimia reported using the DIS. A respondent with the disorder could have a minimum of 7 symptoms and a maximum of 13. Analysis Data analysis was undertaken using mainly Biomedical Data Processing (BMDP) statistical software (Dixon, 1985). Confidence intervals were estimated using either Wilson's approximation to binomial confidence limits for a proportion (Rothman & Boice, 1982), or the exact solution where /> = 0 0 (Diem, 1962). Prevalence estimates from the first interview

673

were obtained by design weighting and poststratification (Wells et al. 1989). Prevalence estimates derived from the clinicians' re-interview of 259 respondents were also ' backweighted' to compensate for re-interview design probabilities. Two hundred and ninetynine respondents were selected for re-interview on the basis of several sets of criteria: depression, possible or definite bulimia, alcohol abuse/ dependence, at random, or any combination of these criteria. A 'backweighting factor' applied to each group selected on the basis of every set or combination of eligibility criteria was derived by taking the ratio of eligibility to successful reinterview, using summed design and poststratification (DPS) weights. RESULTS Response rate A listing of household members was obtained from 94 % of dwellings approached and interviews from 74 % of the potential respondents, yielding an overall response rate of 70 % by the method of Von Korff (1985). The response rate is comparable with similar surveys in New Zealand (Romans-Clarkson et al. 1988), on the West Coast of the United States (Karno et al. 1987), and in Edmonton, Canada (Bland et al. 1988). This yielded 1498 respondents. Of 504 males there were 71 in the 18-24 age group, 265 aged 25-44 and 168 aged 45-64. Of the 994 females, 187 were aged 18-24, 590 aged 25-44 and 217 aged 45-64 years. DIS/DSM-III bulimia prevalence Lifetime prevalence of DIS/DSM-III bulimia for both men and women aged 18-64 (with 95 % confidence interval in brackets) was estimated to be 1-0% (0-6-1-6). The overall lifetime prevalence for males was 0-2% (00-11). For males 18-24 years it was 0-0% (00-51), for 2 5 ^ 4 years it was 0-7 % (0-2-2-6) and for 45-64 years it was 0 0 % (0-0-1-1). The overall lifetime prevalence for females was 1-9% (1-2-30). For females 18-24 years it was 4-5% (2-3-8-5), for 2 5 ^ 4 years it was 2-0% (1-1-3-5) and for 45-64 years it was 0-4% (0-1-2-5). For the group of women aged 18-44 years in whom the disorder was most common, current DIS/DSM-III bulimia (occurring in the last two weeks) had a prevalence of 1 0 % (0-5-2-0),

J. A. Bushnell and others

674

30 -,

Table 1. Characteristics of female respondents

aged 18-44* DSM-III Bulimia (N = 20)

No DSM-III Bulimia (N = 757)

Age (years) 18 24 25 29 30-34 35-39 40-44

41 30 14 II 4

31 40 3 6 / = 11-33 40 P < 005 37

Marital status Married Defacto marriage Separated/divorced Single

31 17 8 43

55 7 / = 6-31 9 NS 28

100 0 0

93 4 / = 1-50 3 NS

Country of origin New Zealand born Born overseas

82 18

87 / = 0-43 13 NS

Parental Social Social Social Social Social Social

5 33 27 20 15 0

12 12 3 5 / = 11-71 32 P < 005 9 7

Parental status Children No children

42 58

58 / = 205 42 NS

Years of education Ten Eleven Twelve Thirteen or more

22 27 35 16

24 31 / = 042 33 NS 12

Race European Maori Other

socio-economic status class I class 2 class 3 class 4 class 5 class 6

5 FIG.

10 15 20 25 30 35 40 44 Age of onset of first symptom (years)

Age at onset of first symptom of bulimia in women aged 18-44 with DIS/DSM-III bulimia in lifetime.

I.

2 0-8 o. |o-6 0-4-

I 0 0 1 2 3 4 5 6 7 8

9 10 111213141516171819202122 Duration in years

FIG. 2. Duration from first to last symptom of bulimia in women aged 18-44 with DIS/DSM-III bulimia in lifetime.

found in other investigations (Robins et al. 1984). Onset and duration

Age of onset of DIS/DSM-III bulimia among the women aged 18-44, explored using un• Figures are design weighted and post stratified percentages. weighted survival analysis, revealed an almost linear increase in the proportion experiencing increasing to 1-5% (0-9-2-6) occurring within their first symptom between the ages of 14 and the past six months, and having occurred at 25 (Fig. 1). Duration from first to last symptom some time in the lifetime of 2-6% (1-7-4-0). The (Fig. 2) revealed a pattern of disorder persisting demographic characteristics of these women are over long periods of time, with only a quarter of described in Table 1. Bulimics were younger those with bulimia ceasing to have symptoms than other women between 18 and 44 years-of- within two years. Three-quarters of those with age, and the social class distribution of their the disorder reported ten or fewer symptoms. parents was not identical, but they did not differ on any of the other demographic variables Comparison of diagnostic criteria examined. In none of the 20 younger women The effect of different diagnostic criteria on the with DIS/DSM-III bulimia was there a history prevalence of disorder in women aged 18-44 was of prior or concurrent anorexia nervosa, explored using second interview clinicians' although the lifetime prevalence of anorexia checklist to determine DSM-III bulimia, draft nervosa (0-1 %) was similar in this study to that DSM-IIIR and Russell's 1979 bulimia nervosa

Prevalence of three bulimia syndromes

syndromes. Clinicians' rating of lifetime prevalence of DSM-III bulimia was 1-7% (10-2-9), and for draft DSM-IIIR criteria was 1-6% (0-9 2-8). Few of those ever meeting criteria for disorder admitted current or recent symptoms. Prevalence of recent disorder (occurring in the past six months) was 0-2 % (0-1—0-9) for clinicianrated DSM-III bulimia and 0-7% (0-3-1-5) for draft DSM-IIIR bulimia nervosa. Comparison of all three syndromes was possible for current disorder (occurring in the last two weeks). Current prevalence estimates were 0-2 % (0-0-0-8) for clinician-rated DSM-III bulimia and 0-5% (0-2-1-3) for draft DSM-IIIR bulimia nervosa. Russell's criteria for bulimia nervosa require vomiting or purging; all respondents meeting the other two criteria for this syndrome denied vomiting or purging, yielding a prevalence estimate of 0 0 % (0-0-0-5). Prevalence of disordered eating behaviour

Although the full syndrome was found to be more rare than some reports have suggested, even as assessed by the first interview DIS, the component behaviours of the DSM-III bulimia syndrome were common. Among women aged 18 44, lifetime experience of recurrent binge eating (using first interview DIS assessment) was reported by 22-5%, depressed mood and selfdeprecating thoughts after bingeing by 10-6 %, at least three disordered eating behaviours (such as use of cathartics, vomiting, fasting) by 8-2%, and fear of being unable to stop a binge by 5-0%. At second interview, the clinicians would appear to have used a narrower definition of recurrent bingeing than that afforded by the DIS. They found a lifetime prevalence of 6-4% for this criterion, about half of whom (3-3 %) were bingeing at least twice weekly. Fear of being unable to stop a binge was reported by 3-6%, and 5-8% described use of extreme diets or diuretics, although only 0-3% had used vomiting or purgatives for weight control. Agreement between first and second interviews

The presence or absence of the DSM-III bulimia syndrome was rated at the first interview using the DIS, and at the second interview twice, first using the DIS, and secondly using semistructured exploration by the clinician to rate DSM-III symptomatology. Agreement has been assessed using Yule's Y, a statistic which varies

675

between — 1 (complete disagreement) and + 1 (complete agreement). Because of its independence of base rates it has been argued that Yule's Y is particularly suitable for dealing with low prevalence disorders where other statistics such as Kappa are of less value (Spitznagel & Helzer, 1985). Interview I DIS v. Interview 2 DIS There was only moderate concordance between first and second interviews on diagnosis of DSM-III bulimia based on the DIS (Yule's Y = 0-66). because the DIS interview skips all subsequent questions on bulimia if the respondent denies binge-eating, inter-item correlations cannot be calculated. However, of the seventeen cases of DSM-III bulimia identified at first interview who were re-interviewed, only six were diagnosed as cases at re-interview. Of these eleven cases positive at first interview but negative on the second, two reported no bingeing so were not further assessed, seven did not meet the B criterion (three of five disordered eating behaviours), eight did not meet the C criterion (fear of inability to stop a binge), and three did not meet the D criterion (depressed mood and self-deprecating thoughts after bingeing). Three who had not met criteria at first interview were diagnosed bulimic by the DIS at reinterview. Of these cases, none met the C criterion at first interview, and two did not meet the B criterion. Interview 2 DIS v. Interview 2 Checklist The second interview DIS showed moderate agreement with the second interview clinician's rating (Yule's Y = 0-76). The amount of agreement is a little less than that achieved for other disorders where lifetime DIS diagnoses by physicians have been compared with physicians' checklist ratings (Helzer el al. 1985). This comparison of the clinician using the DIS against his own rating with the semi-structured interview which followed the DIS administration revealed the source of disagreement again to be the C and B criteria in particular, with the effect that cases moved from disorder to marginal cases and in the other direction with almost equal frequency. Interview I DIS v. Interview 2 Checklist When first interview DIS findings were compared with the second interview clinicians' rating they

676

7. A. Bushnell and others

Table 2. Agreement between ratings of DSM-III criteria for bulimia among women aged 18—44: first interview DIS v. second interview clinician's checklist Second interview clinician's checklist

Number of DSM-III • .

met

First interview DIS Total

f °1 \ 2 3

•

0

1

2

3

4*

Total

86 8 5 6 2 107

2 4 3

0 0 2 4 2 8

1 3 0 3 2 9

0 0 3 3 10 16

89 15 13 18 17 152

2 1 12

•Four criteria means full syndrome present.

yielded a Yule's Y of 058. Investigation of the sources of this disagreement revealed that of seventeen cases identified at first interview as positive (four criteria met) ten were rated positive by a clinician. Blind to the initial interview findings, the clinicians failed to elicit reports of more than minor bingeing in three of these seven cases in which there was disagreement. The remaining four cases, and also the six where disagreement came from cases not diagnosed at first interview but considered to meet criteria by the clinician, were closer to the threshold of disorder on the alternate assessment. The likelihood that two examiners will disagree on diagnosis is greater where cases are clustered around the threshold of disorder, since disagreement on a single symptom can be of diagnostic significance. The clinicians most commonly differed on the assessment of two criteria: having had three of five disordered eating behaviours (B), and fear of inability to stop a binge (C).

DISCUSSION Strengths of this study This study has overcome some of the methodological shortcomings affecting previous research into the prevalence of bulimia and bulimia nervosa. It has sampled a cross section of the general population including adults of both sexes aged 18-64 years, and assessed bulimia using three current definitions of the syndrome. Assessment has been based on interview rather

than self-reported data. The DSM-III bulimia syndrome was assessed using a standardized questionnaire to delineate lifetime, six-month and current prevalence. Reassessment by clinicians blind to the first interview findings explored the clinical relevance of identified symptoms, and rated the presence of draft DSM-IIIR and Russell's Criteria bulimia nervosa as well as the DSM-III syndrome. Limitations of this study Some of the difficulties encountered in other research have also become evident here. First, the response rate was lower than desired. In 6% of selected dwellings no information about the household occupants could be obtained. Of the eligible respondents within households where listings were obtained, 26 % failed to participate, almost all because the selected respondent refused (93 %), yielding an overall response rate of 70%. However, the response rate was still felt to offer reasonable precision. Given that a response rate of 70% has yielded an overall lifetime prevalence of 10 %, it can be shown that even if the response rate among bulimics in the community were as low as half that of the overall response rate, the true overall lifetime prevalence would still only be 2 0 % (Wells et at. 1989). Furthermore, it is unlikely that respondents with bulimia would have had a special reason for non-participation since eating disorders were not mentioned when the respondent was recruited, and were not a primary focus of the interview. Secondly, no data have yet been published to support the reliability or validity of the DIS bulimia section. This study attempted to address the lack of information about the performance of the DIS bulimia section by undertaking a second interview to examine the performance of the DIS and determine the clinical relevance of the identified cases. However, the DIS bulimia section performed inconsistently: it performed better at first interview for some cases, but also missed at first interview identifying some cases diagnosed at second interview. Thirdly, it remains unclear to what extent the interview based data collection dealt with the problem that the disorder is frequently accompanied by secrecy and guilt. Although the semi-structured clinician's interview provided an opportunity for the clinicians to probe and

Prevalence of three bulimia syndromes

encourage disclosure, and did elicit reports of binge eating in some women who denied binge eating in the earlier DIS section of the same interview, it did not elicit acknowledgement of binge eating in some respondents who were identified as cases at the initial interview. The discrepancy between the information obtained at first and second interviews may have been affected by the attributions of the respondents about the purpose of the second interview. The professional status or the gender of the second interviewer may also have influenced the report of symptoms associated with high levels of embarrassment. The degree of variation in the reporting of symptoms at different times suggests that it would be unwise to treat the second interview clinician's rating as a simple confirmation of 'caseness'. First interview findings

Although re-evaluation of positive and borderline cases by a clinician blind to initial interview findings revealed disagreement about which borderline cases should have been included and excluded, prevalence rates were comparable to those of the initial layadministered DIS for the DSM-III bulimia syndrome. The disagreement has had relatively little impact on estimates of rates of disorder. The overall lifetime prevalence for the disorder was 1-0%. However, the disorder was found to be rare in males and in older women, and more common in younger women. The higher lifetime prevalence among younger women is consistent with an increasing incidence in recent years, although other factors may also contribute to this finding. It may reflect a bias against reporting the disorder in older women, a general perception of the disorder being one of young women, or a failure of recall in the older women. However, the cohort effect was so strong that these factors are barely credible as a complete explanation. Among those with the full DIS/DSM-III syndrome, first symptoms began between age 14 and 25, and only a quarter of those with the disorder were symptom-free within two years. By comparison with those women aged 18-44 without bulimia, the demographic characteristics of those with bulimia such as years of education, country of origin, marital status, and whether they had children, were all comparable.

677

The disorder was not disproportionately common among more educated women. It has been found that disordered eating behaviour is common, especially among younger women. The first interview findings suggested that approximately one in five women aged 18-44 engaged in recurrent binge eating, about half of those experiencing depressed mood or self-deprecating thoughts in response to bingeing, and almost half of these binge eaters engaging in other disordered eating behaviour, such as use of cathartics, rigorous fasting or secretive eating. A quarter of those binge eating had been afraid of being unable to stop a binge. However, only one woman in forty aged 18 4 4 had ever met all the DSM-III criteria for bulimia, and one in a hundred currently experienced the disorder. The existence of a continuum of disordered eating behaviour has been discussed in relation to anorexia nervosa (Garner et al. 1983 a). Copeland (1981) has cogently argued that the criteria for defining the existence of a case may depend on the purpose for which that decision is made. Whether the purpose of identifying a case of bulimia is the identification of risk factors, prediction of natural history, or response to treatment, the evidence is fragmentary and incomplete as to where cutpoints should be placed on a continuum of disturbed behaviour, or indeed what features are essential in order to define a case for that purpose. DSMIII offers clarity and certainty, although for bulimia as for other disorders, the relevance of the syndrome it defines to any specific purpose is largely undetermined. The index of severity of bulimia (the number of symptoms of bulimic disorder) suggests that the majority of the cases meeting criteria were in the mild to moderate end of a spectrum of severity. The extent to which findings within this group of disordered individuals in the community are relevant to a clinical population is unclear, and further research comparing community and clinical populations is needed to elucidate this issue. Second interview findings

In a semistructured interview the clinicians appeared to use a more restricted definition of binge eating than the DIS, as they found that one younger woman in twenty had engaged in recurrent binge eating, half of them two times or

678

J. A. Bushnell and others

more weekly. Most of these bingers had been afraid of being unable to stop a binge, and had engaged in disordered eating behaviour such as fasting or use of diuretics, although few had engaged in vomiting or purging. The lifetime prevalence of DSM-III bulimia based on clinician's assessment was about twothirds the rate based on the lay interviewers' DIS/DSM-III data, and similar to the prevalence of DSM-IIIR bulimia nervosa, although different individuals were identified by the latter syndrome. Comparison of the clinician rated DSM-III, DSM-IIIR and Russell's Criteria syndromes was possible for current prevalence. The prevalence rates of the DSM-III and DSM-IIIR syndromes were in the same general range as some North American estimates among college students. Schotte & Stunkard (1987) found prevalence in the range 0-6—1-8 %, (95% Confidence Interval), and Pyle et al. (1986) 0-5-2-0 %, in comparison with 0-0%-08% in this study. The DSM-IIIR prevalence of Schotte & Stunkard (1987) is remarkably close to that found in this study (0-3-1-4% v. 0-2-1-3%). Russell's Criteria bulimia nervosa was more rare in this general population sample than found in British studies. Two studies of familyplanning clinic attenders conducted by Cooper et al. (1987) and Cooper & Fairburn (1983), found a prevalence of bulimia nervosa of 1-8% (0-8-3-9%) and 1-9% (0-9-3-9%) respectively. No cases of Russell's Criteria bulimia nervosa were identified in this general population sample, yielding a prevalence estimate within the range 0-0-0-5%. It is possible that this finding reflects a difference in the prevalence of disturbed eating behaviour unique to New Zealand culture. But the high prevalence of disordered eating behaviour, and similar findings to other recent research using different syndrome definitions suggests cultural similarity. The difference is more likely to be due to sampling strategy. The use of a cross-sectional probability sample of the adult general population has an advantage over less direct methods of recruitment in that it is not influenced by the factors governing access to the point within the health or education system at which recruitment has occurred in many other studies.

Diagnosis and the dimension of time Current prevalence estimates are considerably lower than lifetime prevalences and at first sight this would seem to contradict the evidence from survival analysis which suggested that the symptoms of the disorder persist for long periods of time. With the exception of the clinician's rating of DSM-III disorder (where current disorder was more rare), about one-third of those identified as having ever met criteria for disorder in their lifetime experienced current symptoms. However, this difference between rates of lifetime and current disorder is consistent with an intermittent and fluctuating course of disorder. If symptoms come and go over time, the likelihood of symptoms occurring will obviously be less in any short period of time such as two weeks, then in a longer period such as a year or ever in the person's lifetime. The assessment of lifetime prevalence by the DIS has been criticized on the grounds that sixmonth rates of disorders are comparable with other studies using different methods, but lifetime rates are lower (Parker, 1987). Parker has argued that this result suggests that there are major problems of recall for distant events, and that the validity of the DIS and its use by lay interviewers is therefore questionable. However, problems of recall in bulimia may be less of an issue than in some other disorders. The fact that bulimia occurs among younger women means that they have had less time to forget. Furthermore, the long duration from first to last symptom in those who have recovered suggests a protracted sensitivity to weight related issues and an ongoing concern with food which would militate against forgetting. CONCLUSION Within the general population DSM-III bulimia is found predominantly in younger women, and this may reflect a growing incidence of the disorder. Although the types of disordered behaviour surrounding eating and food which constitute the elements of the bulimia syndrome are common, prevalence of the syndrome among younger women in the general community is similar to more conservative estimates of prevalence of DSM-III bulimia within female college

Prevalence of three bulimia syndromes

students. Early claims of the disorder forming an epidemic of vast proportions throughout the western world would seem to have been overstated. This research was jointly funded by the Medical Research Council of New Zealand, the Canterbury Medical Research Foundation, and the Alcoholic Liquor Advisory Council. We wish to thank the interviewing team for their contribution, and the participants in the study for making it possible. Dr Chris Fairburn's helpful comments on an earlier draft of this paper are gratefully acknowledged. REFERENCES Abraham, S. R. & Beumont, P. J. V. (1982). How patients describe bulimia or binge eating. Psychological Medicine 12, 625-635. American Psychiatric Association (1980). Diagnostic and Statistical Manual of Mental Disorders (3rd edition). American Psychiatric Association Press: Washington, DC. American Psychiatric Association (1985) DSM-IIIR In Development. American Psychiatric Association Press: Washington, DC. Ben-Tovim, D. 1., Subbiah, N., Scheutz, B. & Morton, J. (1989). Bulimia: symptoms and syndromes in an urban population. Australian and New Zealand Journal of Psychiatry 23, 73-80. Bland, R. C , Newman, S. C , & Orn, H. (eds) (1988). Epidemiology of psychiatric disorders in Edmonton. Ada Psychiatrica Scandinariea 77, Suppl. No. 338. Cooper, P. J. & Fairburn, C. G. (1983). Binge eating and self-induced vomiting in the community: a preliminary study. British Journal of Psychiatry 142, 139-144. Cooper, P. J., Charnock, D. & Taylor, M. J. (1987). The prevalence of bulimia nervosa: a replication study. British journal of Psychiatry 151, 684-686. Copeland, J. (1981). What is a case? A case for what? In What is a case? The Problem of Definition in Psychiatric Community Surveys (ed. J. K. Wing, P. Bebbington and L. Robins), pp. 9-11. Grant Mclntyre: London. Crowther, J. H., Post, G. & Zaynor, L. (1985). The prevalence of bulimia and binge eating in adolescent girls. International Journal of Eating Disorders 4, 29-42. Diem, K. (ed.) (1962). Documenta Geigy: Scientific Tables (6th edn). Geigy. Basle, Switzerland. Dixon, W. J. (ed) (1985). BMDP Statistical Software. University of California Press: Berkeley. Drenowski, A., Yee, D. K. & Krahn, D. D. (1988). Bulimia in college women: incidence and recovery rales. American Journal of Psychiatry 145, 753-755. Fairburn, C. G. & Cooper, P. J. (1982). Self induced vomiting and bulimia nervosa: an undetected problem. British Medical Journal 284, 1153 1155. Fairburn, C. G. & Cooper, P. J. (1984). Binge eating, self induced vomiting and laxative abuse: a community study. Psychological Medicine 14, 401-410. Garner, D., Olmsted, M. & Garfinkel, P. (1983a). Does anorexia nervosa occur on a continuum ? International Journal of Eating Disorders IS, 11-20. Garner, D., Olmsted, M. & Polivy, J. (1983ft). Development and validation of a multidimensional Eating Disorder Inventory for anorexia nervosa and bulimia. International Journal of Eating Disorders 78, 89 95. Gray, J. & Ford, K. (1985). Incidence of bulimia in a college sample. International Journal of Eating Disorders 4, 210-210. Halmi, K. A., Falk, J. R. & Schwartz, E. (1981). Binge eating and

679

vomiting: a survey of a college population. Psychological Medicine 11, 697-706. Hart, K. J. & Ollendick, T. H. (1936). Prevalence of bulimia in working and university women. American Journal of Psychiatry 142, 851-854. Helzer, J. E., Robins, L. N., McEvoy, L. T., Spilznagel, E. L., Stoltzman, R. K., Farmer, A. & Brockington, I. F. (1985). A comparison of clinical and Diagnostic Interview Schedule diagnoses: physician re-examination of lay-interviewed cases in the general population. Archives of General Psychiatry 42, 657 666. Johnson, C. L., Stuckey, M. K., Lewis, L. D. & Schwartz, D. M. (1982). Bulimia: a descriptive survey of 316 cases. International Journal of Eating Disorders 2, 3-18. Johnson, C , Lewis, C , Love, S., Lewis, S. & Stuckey, M. (1984). Incidence and correlates of bulimic behaviour in a female highschool population. Journal of Youth and Adolescence 13, 15 26. Karno, M., Hough, R. L., Burnam, A., Escobar, J. I., Timbers, D. M., Santana, F. & Boyd, J. H. (1987). Lifetime prevalence of specific psychiatric disorders among Mexican Americans and nonHispanic whites in Los Angeles. Archives of General Psychiatry 44, 695-701. Kish, L. (1965). Survey Sampling. Wiley: New York. Nevo, S. (1984). Bulimic symptoms: prevalence and ethnic differences among college women. International Journal of Eating Disorders 4, 151-168. Parker, G. (1987). Are the lifetime prevalence estimates in the ECA study accurate? Psychological Medicine 17, 275 282. Pope, H. G., Hudson, T. L. & Yurgelun-Todd, D. (1984). Anorexia nervosa and bulimia among 300 suburban women shoppers. American Journal of Psychiatry 141, 187-190. Pope, H. G., Hudson, V. I., Yurgelun-Todd, D. & Hudson, M. S. (1985). Prevalence of anorexia nervosa and bulimia in three student populations. International Journal of Eating Disorders 3, 45-55. Pyle, R. L., Halvorson, P. A., Newman, P. A. & Mitchell, J. E. (1986). The increasing prevalence of bulimia in freshmen college students. International Journal of Eating Disorders 5, 631-647. Pyle, R. L., Mitchell, J. E. Eckert, E. D., Halvorson, P. A., Neuman, P. A. & Goff, G. M. (1983). The incidence of bulimia in freshman college students. International Journal of Eating Disorders 2, 75-85. Regier, D. A., Myers, J. K., Kramer, M., Robins, L. N., Blazer, D. G., Hough, R. L., Eaton, W. W. & Locke, B. Z. (1984). The NIMH Epidemiologic Catchment Area Program. Archives of General Psychiatry 41, 934-941. Robins, L. N., Helzer, J. E., Croughan, J. & Ratcliff, K. S. (1981). National Institute of Mental Health Diagnostic Interview Schedule: its history, characteristics and validity. Archives of General Psychiatry 38, 381-389. Robins, L. N., Helzer, J. E., Weissman, M. M., Orvaschel, H., Gruenberg, E., Burke, J. & Regier, D. A. (1984). Lifetime prevalence of specific psychiatric disorder in three sites. Archives of General Psychiatry 41, 949-958. Romans-Clarkson, S. E., Walton, V. A., Herbison, G. P. & Mullen, P. E. (1988). A study of women who refuse to participate in a community study of psychiatric disorder. Australian and New Zealand Journal of Psychiatry 22, 19-29. Rothman, K. J. & Boice, J. D. (1982). Epidemiologic Analysis with a Programmable Calculator. Epidemiology Resources: Boston. Russell, G. (1979). Bulimia nervosa, an ominous variant of anorexia nervosa. Psychological Medicine 9, 429-448. Schotte, D. E. & Stunkard, A. J. (1987). Bulimia v. bulimic behaviors on a college campus. Journal of the American Medical Association 258, 1213-1215. Spitznagel, E. L. & Helzer, J. E. (1985). A proposed solution to the base rate problem in the Kappa statistic. Archives of General Psychiatry 42, 725-728. Stangler, R. S. & Prinlz, A . M . (1980). DSM-III: psychiatric diagnosis in a university population. American Journal of Psychiatry 137, 937 940. Von Korff, M., Cottier, L., George, L. K., Eaton, W. W., Leaf, P. i.

680

J. A. Bushnell and others

& Burnam, A. (1985). Non response and non response bias in the ECA Surveys. In Epidemiohgic Field Methods in Psychiatry (ed. W. W. Eaton and L. G. Kessler), pp. 85-98. Academic Press: London. Welch, G. & Hall, A. (in the press). The reliability and discriminant validity of three potential measures of bulimic behaviours. Journal of Psychiatric Research. Wells, J. E., Bushnell, J. A., Oakley-Browne, M. A., Joyce, P. R. &

Hornblow, A. R. (1989). Christchurch Psychiatric Epidemiology Study: methodology and lifetime prevalence for specific psychiatric disorders in Christchurch, New Zealand. Australian and New Zealand Journal of Psychiatry 23, 315-326. Zuckerman, D. M., Colby, A., Ware, N. C. & Lazerson, J. S. (1986). The prevalence of bulimia among college students. American Journal of Public Health 76, 1135 1137.