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Stability of Eating Disorder Diagnostic Classifications in Adolescents: Five-Year

Longitudinal Findings From a Population-Based Study

DIANN M. ACKARD Private Practice; and Division of Epidemiology and Community Health, School of Public

Health, University of Minnesota, Minneapolis, Minnesota, USA

JAYNE A. FULKERSON School of Nursing, University of Minnesota, Minneapolis, Minnesota, USA

DIANNE NEUMARK-SZTAINER Division of Epidemiology and Community Health, School of Public Health, University

of Minnesota, Minneapolis, Minnesota, USA

This study examined the stability of eating disorder (ED) clas- sifications among a population-based sample of male and female adolescents (n = 2,516) who participated in Project EAT-II, a five-year longitudinal study. Cross-tabulations using weighted data identified diagnostic stability across six classifica- tions (Anorexia Nervosa, Bulimia Nervosa, Binge Eating Disorder, Binge Eating and/or Compensatory Behaviors not meeting ED diagnosis, Body Image Disturbance without disordered eating, and Asymptomatic). One-third (32.6%) of adolescents who were asymptomatic at baseline and over half of those who were symp- tomatic at baseline reported symptoms five years later. All males and 82% of females with a threshold diagnosis at baseline remained symptomatic five years later, but rarely within the same

Parts of this manuscript were presented at the annual meeting of the Academy for Eating Disorders in May, 2008 in Seattle, WA.

This study was supported by grants R40 MC 00319 and R40 MC 00319-02 from the Maternal and Child Health Bureau (Title V, Social Security Act), Health Resources and Services Administration, Department of Health and Human Services (D. Neumark-Sztainer, principal investigator).

Address correspondence to Diann M. Ackard, PhD, LP, 5101 Olson Memorial Highway, Suite 4001, Minneapolis, MN 55422, USA. E-mail: [email protected]

308

Eating Disorder Diagnostic Stability 309

classification. In conclusion, the presence of ED symptoms in ado- lescence strongly predicts ED symptoms five years later. ED diag- noses and classifications were unstable over time, underscoring the critical need for prevention efforts and periodic assessment and encouraging early detection and intervention among adolescents.

In clinical populations of adults with eating disorders, it has been well documented that eating disorder diagnoses are unstable over time (Eddy et al., 2008; Fichter & Quadflieg, 2007; Keel, Mitchell, Miller, Davis, & Crow, 1999; Milos, Spindler, Schnyder, & Fairburn, 2005; Quadflieg & Fichter, 2003; Shisslak, Crago, & Estes, 1995; Tozzi et al., 2005). This may be, in part, due to patients improving throughout the course of treatment, or worsening by adopting new and different means to influence weight. An important ques- tion, with implications for eating disorder classifications and for the planning of interventions, regards the stability of these problems over time; however, many affected individuals do not receive or seek treatment for an eating disorder, and thus is it important to understand the diagnostic presenta- tion and fluctuation among non-clinical samples. For example, disordered eating behaviors and body image concerns have been found to fluctuate among a non-clinical sample of adult college students followed over 20 years (Keel, Baxter, Heatherton, & Joiner, 2007). Yet only a few studies have investigated fluctuations in disordered eating behaviors and body dispar- agement during adolescence (Sancho, Arija, Asorey, & Canals, 2007; Stice, Marti, Shaw, & Jaconis, 2009), a time often identified as high risk for the onset of significant eating disturbances (Shisslak, Crago, & Estes, 1995; Stice et al., 2009). Investigating the stability (or instability) of eating and body image disturbances among youth serves to elucidate whether early detec- tion and intervention efforts are necessary among younger populations in order to avoid or lessen the quality of life (Bamford & Sly, 2010) and finan- cial (Crow et al., 2009) ramifications of eating disorders evident among adult populations.

Findings from a two-year follow-up study of 200 Spanish boys and girls aged 9–13 indicate that while most youth do not engage in disordered eating, of those youth who did endorse eating disturbances, the most common diagnosis was eating disorder not otherwise specified (EDNOS; Sancho et al., 2007). Of the 21 boys and 25 girls who demonstrated disordered eating disturbances at Time 1, scores at Time 2 indicated that for some individuals (11 boys, 6 girls) symptoms had remitted. For a few others (2 boys, 4 girls) symptoms had been confirmed as an eating disorder, and for the remaining individuals (4 boys, 14 girls) symptoms had shifted to a different cluster of behaviors (Sancho et al., 2007).

More recently, an eight-year longitudinal study of a community sample of 496 adolescent girls found significant fluctuations over the study period,

310 D. M. Ackard et al.

including improvement in symptoms congruent with recovery and remis- sion, as well as diagnostic migration, most commonly and bidirectionally between bulimia nervosa (BN) and binge eating disorder (BED; Stice et al., 2009). Specifically, over 90% of the 32 and 24 girls with subthreshold or threshold BN or BED, respectively, diagnosed at any point in the study, were determined to be in remission one year later, and the percentage in remission rose to 100% within two years of diagnosis. However, across the entire follow-up period, the picture is less promising, with relapse rates approximately 30–40% across the eight-year study duration. Furthermore, migration from one eating disorder diagnosis to another was evident across all diagnoses over the course of the follow-up period. For example, of those with BN at baseline, 19% migrated to BED at follow-up; of those with BED at baseline, 42% migrated to BN and 4% migrated to purging disorder at follow-up.

Assessing the fluctuation of disordered eating over time, particularly from early to older adolescence, is important for health promotion among youth. Stice and colleagues conducted eight annual assessments with adoles- cent girls starting in 7th-8th grade (Stice et al., 2009). Of those who did not already have an eating disorder diagnosis at baseline, the peak period of risk for an eating disorder was between ages 15 and 17 for BN. A more gradual progression of risk from age 16 to 19 was evident for BED. Unfortunately, there were no data provided regarding peak risk for anorexia nervosa (AN; likely due to no or too few cases of AN within the study sample), nor for sub- threshold symptomatic classifications that may best describe the majority of symptomatic youth (Ackard, Fulkerson, & Neumark-Sztainer, 2007; Shisslak et al., 1995).

The current study aims to evaluate the stability of eating disor- der diagnoses and classifications over a five-year period among a large population-based sample of female and male adolescents. Participants were followed during key periods of transition during adolescence and early young adulthood, and the sample was specifically weighted for ethnic diver- sity to aid in generalization to other samples across the United States. Data were analyzed to determine the stability across six eating disorder classifications, ranging from full threshold eating disorder to no eating disorder or body image symptoms. The six classifications included three threshold symptomatic diagnoses (AN, BN, and BED), two subthreshold symptomatic diagnoses (Binge Eating/Compensatory Behaviors not meet- ing full diagnostic criteria and Body Image Disturbance without disordered eating behaviors), and one asymptomatic classification, indicating no symp- toms or behaviors of an eating or body image disorder. These classifications were based on previous empirical research evaluating the clinical utility of eating disorder diagnoses among a school-based sample of youth (Ackard et al., 2007). Examining patterns among a sample of older adolescents can help with our understanding of the prevalence and stability of eating

Eating Disorder Diagnostic Stability 311

disorder diagnoses during a critical time in youth development; the years between adolescence and young adulthood are identified as high risk for the development or worsening of eating disorder symptoms (Stice et al., 2009). Furthermore, results from the current study will help to determine the patterns of symptom changes in both males and females that might influence targeted treatment and intervention approaches. Similar to results found in clinical populations, we hypothesized that we would find poor eating disorder diagnostic stability across the five-year study period, among both male and female older adolescents.

METHOD

Study Population

Data were drawn from Project EAT, an epidemiologic study of adolescent eating behaviors and weight-related issues with two times of data col- lection from the same individuals, five years apart (Time 1 in 1999 and Time 2 in 2004; mean age 20.4 at follow-up assessment, SD = 0.8; Neumark- Sztainer, Story, Hannan, & Croll, 2002; Neumark-Sztainer, Story, Hannan, Perry, & Irving, 2002). Project EAT participants were from 31 public middle and high schools in urban and suburban school districts in the greater St. Paul/Minneapolis, Minnesota area. Participants were diverse by age, race, BMI, and socioeconomic status. Each Time 1 participant completed Project EAT surveys and anthropometric measures of height and weight. At Time 1, consent procedures were completed in accordance with the requirements of the participating schools’ research boards. In some schools, parents were required to return signed consent forms agreeing to have their child par- ticipate in the study; in other schools, parents were only required to return signed consent forms if they did not want their child to participate. All Time 1 participants signed an assent form before survey completion. At Time 2, par- ents of adolescents younger than age 18 were sent a consent form before sending out the surveys; surveys were not sent to adolescents whose par- ents mailed back a signed consent form indicating their refusal to have their child participate. Adolescents were then sent an assent form with the sur- vey and asked to sign and return the form if they were not interested in study participation. Completion of the survey at Time 2 implied written con- sent. Approval for the study was granted by the University of Minnesota’s Institutional Review Board Human Subjects Committee and by the research boards of the participating school districts.

Only Time 1 participants were eligible to participate in the Time 2 assess- ment; no new participants were recruited for Time 2 who did not participate in Time 1. The Project EAT Time 2 surveys were sent by mail to the address provided by the participant during Time 1. Data collection ran from April 2003 to June 2004. Of the original Time 1 cohort, 1,074 (22.6%) were lost to

312 D. M. Ackard et al.

follow-up for various reasons, primarily missing contact information at Time 1 and no address found at follow-up. Of the remaining 3,672 participants con- tacted, 2,516 completed surveys, representing 53% of the original cohort and 68.4% of participants who were contacted for Time 2.

For the current study, the final sample included 2,516 youth (45% males; 55% females) who completed the Project EAT Time 1 survey and also completed the Project EAT Time 2 survey. The sample was well- distributed across socioeconomic status; 17.8% in the lower quintile, 18.9% lower-middle, 26.7% middle, 23.3% upper middle, and 13.3% upper quintile. Participants described themselves as white (48.3%), Asian (19.6%), black (18.9%), Hispanic (5.8%), or mixed/other (3.8%) ethnicity/race.

Each DSM-IV (American Psychiatric Association [APA], 1994) criterion for AN, BN and BED was mapped to survey questions based on discussions and consensus by a multidisciplinary group of researchers and clinicians with expertise in the field. Project EAT items were selected based on how well the items represented each clinical criterion within the DSM-IV diagnos- tic classification. The mapping of Project EAT survey items to each criterion is described in detail in another publication (Ackard et al., 2007) and spe- cific criterion are outlined below by Threshold Symptomatic, Subthreshold Symptomatic, and Asymptomatic categories. The eating disorder classifica- tions among the current study sample at baseline (Time 1) were: AN (n = 0 female, 0 males), BN (n = 10 females, 0 males), BED (n = 18 females, 6 males), Binge Eating and/or Compensatory Behaviors not meeting threshold diagnoses (n = 321 females, 185 males), Body Image Disturbance without disordered eating (n = 301 females, 180 males), and Asymptomatic (n = 736 females, 759 males).

Measures

The following eating disorder classifications were measured via self- report using questions from the Project EAT survey. Using the available survey items, criteria for each classification described below were deter- mined following discussions and consensus by a multidisciplinary group of researchers and clinicians with expertise in the field (see Ackard, Fulkerson, & Neumark-Sztainer, 2007).

THRESHOLD SYMPTOMATIC

Anorexia Nervosa. Criterion A (refusal to maintain body weight at or above a minimally normal weight for age and height) is met if the partic- ipant’s observed BMI is less than the 15th percentile for age and gender, and the participant responds “yes” to the question, “During the past year have you done anything to try to lose weight or keep from gaining weight?” Criterion B (intense fear of gaining weight or becoming fat, even though

Eating Disorder Diagnostic Stability 313

underweight) is met if an underweight (BMI < 15th percentile) participant answers “strongly agree” to the statement, “I am worried about gaining weight.” Criterion C (disturbance in the way in which one’s body weight or shape is experienced, undue influence of body weight or shape on self- evaluation, or denial of the seriousness of the current low body weight) could be met: (a) if an underweight (BMI < 15th percentile) participant responds that they are “somewhat overweight” or “very overweight”; (b) if the participant responds, “weight and shape were among the main things that affected how I felt about myself” or “weight and shape were the most important things that affected how I felt about myself” to the question “During the past six months, how important has your weight or shape been in how you feel about yourself?”; or (c) if an underweight (BMI < 15th per- centile) participant responds that his or her best weight is less than his or her observed weight when answering the question, “At what weight do you think you would look best?” Criterion D (amenorrhea) was not assessed in the original Project EAT survey.

Bulimia Nervosa. Criterion A (recurrent episodes of binge eating) is met if the participant answers “yes” to both of the following: (a) “In the past year, have you ever eaten so much food in a short period of time that you would be embarrassed if others saw you (binge eating)?” and (b) “During the times when you ate this way, did you feel you couldn’t stop eating or control what or how much you were eating?” Criterion B (recur- rent inappropriate compensatory behavior) is met if the participant answers “yes” to either of the behaviors listed in the question, “During the past week, did you do any of the following to lose weight or keep from gain- ing weight . . . made myself vomit (throw up)? Used laxatives?” or reported engaging in 12 or more hours per week of moderate (not exhausting, such as walking quickly, baseball, gymnastics, easy bicycling, volleyball, skiing, dancing, skateboarding, snowboarding) and strenuous exercise (heart beats rapidly, such as biking fast, aerobic dancing, running, jogging, swimming laps, rollerblading, skating, lacrosse, tennis, cross-country skiing, soccer, basketball, football). Criterion C (binge eating and inappropriate compen- satory behaviors both occur, on average, at least twice a week for three months) is met when the participant responds “nearly every day” or “a few times a week” to the question, “How often, on average, did you have times when you ate this way—that is, large amounts of food plus the feeling that your eating was out of control?” and reported “yes” to vomiting or using laxatives in response to the question, “During the past week, did you do any of the following to lose weight or keep from gaining weight?” or reported at least 12 hours per week of moderate or strenuous exercise. Criterion D is met if the participant responds “weight and shape were among the main things that affected how I felt about myself” or “weight and shape were the most important things that affected how I felt about myself” to the question “During the past six months,

314 D. M. Ackard et al.

how important has your weight or shape been in how you feel about yourself?”

Binge Eating Disorder. Criterion A (recurrent episodes of binge eat- ing) is met if the participant answers “yes” to both of the following: (a) “In the past year, have you ever eaten so much food in a short period of time that you would be embarrassed if others saw you (binge eating)?” and (b) “During the times when you ate this way, did you feel you couldn’t stop eating or control what or how much you were eating?” Criterion B (binge eating episodes are associated with three or more of the following: eating much more rapidly than normal, eating until feeling uncomfortably full, eating large amounts of food when not feeling physically hungry, eat- ing alone because of being embarrassed by how much one is eating, and feeling disgusted with oneself, depressed, or very guilty after overeating) is unable to be mapped because similar questions were not included in the Project EAT survey. Criterion C (marked distress regarding binge eating) is met if the participant meets Criterion A and answers “some” or “a lot” to the question, “In general, how upset were you by overeating (eating more than you think is best for you)?” Criterion D (frequency of binge eating at least two days a week for six months) is met if the participant meets Criterion A and answers “nearly every day” or “a few times a week” to the question, “How often, on average, did you have times when you ate this way—that is, large amounts of food plus the feeling that your eating was out of control?” Criterion E (binge eating is not associated with the regu- lar use of inappropriate compensatory behaviors) is met if the participant answers “no” to both of the compensatory behaviors listed in the question, “During the past week, did you do any of the following to lose weight or keep from gaining weight . . . made myself vomit (throw up)? Used laxa- tives?” and reports engaging in less than 12 hours of moderate and strenuous exercise.

SUBTHRESHOLD SYMPTOMATIC

Binge eating/Compensatory behaviors. Individuals included in this clas- sification could report Binge Eating and/or Compensatory Behaviors not meeting criteria for Bulimia Nervosa or Binge Eating Disorder as noted above, and could have any level of body image disturbance as noted below. More specifically, individuals were classified into this category if they endorsed engaging in binge eating behaviors (see Criteria A and B for Binge Eating Disorder, above) but did not report significant distress regard- ing the binge eating (see Criterion C for Binge Eating Disorder, above) or did not meet frequency criteria for Binge Eating Disorder (see Criterion D for Binge Eating Disorder, above). Other individuals were classified into this “Binge Eating/Compensatory Behaviors” classification if they reported the use of compensatory behaviors (see Criterion B for Bulimia Nervosa, above)

Eating Disorder Diagnostic Stability 315

but did not meet frequency criteria for Bulimia Nervosa (see Criterion C for Bulimia Nervosa, above).

Body image disturbance. Individuals in this category did not report binge eating and did not report the use of compensatory behaviors. They were classified as having “Body Image Disturbance” if they responded “weight and shape were among the main things that affected how I felt about myself” or “weight and shape were the most important things that affected how I felt about myself” to the question “During the past six months, how important has your weight or shape been in how you feel about yourself?” (same as Criterion D for Bulimia Nervosa).

ASYMPTOMATIC

Individuals were classified as asymptomatic if they did not report binge eat- ing, did not report the use of compensatory behaviors, and, to the question “During the past six months, how important has your weight or shape been in how you feel about yourself?” responded either that “weight and shape were not very important” or “weight and shape played a part in how I felt about myself.”

Data Analysis

Crosstabulations were conducted to assess diagnostic transition from Time 1 to Time 2. Crosstabulations were conducted at the Threshold Symptomatic/Subthreshold Symptomatic/Asymptomatic level as well as at the finer eating disorder classification level. Data were weighted to adjust for differential response rates in the Project EAT Time 2 survey with the use of the response propensity method (Little, 1986). All weighted values are rounded where case numbers are reported. All analyses were conducted with SAS software, version 9.1.

RESULTS

Progression of Diagnostic Severity Among Males

Table 1 presents the stability of eating disorder classifications from Time 1 to Time 2 among male adolescents. Nearly 30% of male adolescents who were asymptomatic at Time 1 developed some type of problem by Time 2; 12.1% developed a body image disturbance, 14.9% reported binge eating or com- pensatory behaviors, and 0.5% developed either BED or BN. Furthermore, 40–45% of those with subthreshold symptoms at Time 1 remained symp- tomatic at the subthreshold or threshold level at Time 2. With respect to threshold diagnoses, although there were no cases of Anorexia Nervosa at either Time 1 or Time 2, and no cases of Bulimia Nervosa at Time 1, four

TA B

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D ia

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ab ili

ty o f E at

in g

D is

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A cr

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5 Y ea

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o m

A d o le

sc en

ce to

E ar

ly Y o u n g

A d u lth

o o d : M

al es

E at

in g

d is

o rd

er cl

as si

fi ca

tio n

at tim

e 2

(M al

es )

Su b th

re sh

o ld

sy m

p to

m at

ic T h re

sh o ld

sy m

p to

m at

B o d y

B in

ge B

in ge

im ag

e ea

tin g/

co m

p en

sa to

ry ea

tin g

B u lim

ia A

n o re

xi a

A sy

m p to

m at

ic d is

tu rb

an ce

b eh

av io

r d is

o rd

er n er

vo sa

n er

vo sa

(n =

76 0)

(n =

17 3)

(n =

18 7)

(n =

5) (n

= 4)

(n =

E at

in g

d is

o rd

er cl

as si

fi ca

tio n

at T im

e 1

(m al

es )

A sy

m p to

m at

ic (n

= 75

9) 72

.6 %

12 .1

% 14

.9 %

0. 2%

0. 3%

0. 0%

Su b th

re sh

o ld

sy m

p to

m at

ic B

o d y

im ag

e d is

tu rb

an ce

(n =

18 0)

60 .7

% 25

.3 %

11 .8

% 1.

3% 0.

9% 0.

B in

ge ea

tin g/

co m

p en

sa to

ry b eh

av io

r (n

= 18

5) 54

.0 %

17 .1

% 28

.0 %

0. 9%

0. 0%

T h re

sh o ld

sy m

p to

m at

ic B

in ge

E at

in g

D is

o rd

er (n

= 6)

0. 0%

75 .7

% 24

.3 %

0. 0%

B u lim

ia N

er vo

sa (n

= 0)

N / A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) A

n o re

xi a

N er

vo sa

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

N o te

: A

ll n s

ar e

w ei

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d .

N / A

= n o t ap

p lic

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b ec

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th er

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vo sa

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B u lim

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sa am

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m al

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T im

e 1.

316

Eating Disorder Diagnostic Stability 317

cases of Bulimia Nervosa emerged by Time 2, and all cases of BED at Time 1 remained symptomatic at Time 2.

Progression of Diagnostic Severity Among Females

Table 2 shows the migration across eating disorder classifications from Time 1 to Time 2 among female adolescents. Nearly 40% of the girls who were asymptomatic at Time 1 developed problems during middle or late adolescence. Furthermore, among the 301 girls at Time 1 with body image disturbance who did not endorse any binge eating or use of compensatory behaviors, nearly 30% worsened such that they reported binge eating, the use of compensatory behaviors, or met threshold diagnostic criteria for BN or BED. Furthermore, while 40.2% of those in the Binge Eating/Compensatory Behavior classification at Time 1 remained in that same classification at Time 2, 3.7% worsened to meet threshold criteria for BED or BN. Finally, less than one-fifth of the girls with BED or BN at Time 1 were able to become asymptomatic at Time 2.

DISCUSSION

The current study used data from a large, population-based study of male and female adolescents to evaluate the stability of eating disorder classi- fications over a peak period of eating disorder development (Stice et al., 2009). Because the majority of youth who endorse disordered eating and body image concerns do not meet criteria for an eating disorder (Shisslak et al., 1995) according to DSM-IV diagnostic criteria (APA, 1994), we included subthreshold classifications, previously derived (Ackard et al., 2007), in addi- tion to threshold diagnoses of anorexia nervosa, bulimia nervosa, and binge eating disorder. Our findings show that nearly 30% of male adolescents and 40% of female adolescents without any eating or body image distur- bance at Time 1 developed problems by Time 2. Of concern, approximately 15% of the male adolescents and 30% of the female adolescents who only displayed body image disturbance at Time 1 worsened by Time 2, and reported either binge eating, the use of compensatory behaviors, or met threshold diagnostic criteria for BN or BED. Among youth meeting cri- teria for a subthreshold symptomatic classification at Time 1, nearly half of the boys and two-thirds of the girls remained symptomatic at Time 2, with several cases progressing to meet criteria for a threshold eating disorder.

Results from the current study underscore the critical need for pre- vention efforts and early detection among adolescents. An alarmingly high number of adolescents went from being asymptomatic to having either subthreshold or threshold conditions over the five-year study period,

TA B

LE 2

D ia

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ab ili

ty o f E at

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D is

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5 Y ea

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A d u lth

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m al

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d is

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as si

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(F em

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Su b th

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sy m

p to

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sh o ld

sy m

p to

m at

B o d y

B in

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in ge

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(n =

67 9)

(n =

31 2)

(n =

36 4)

(n =

10 )

(n =

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(n =

E at

in g

d is

o rd

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as si

fi ca

tio n

at T im

e 1

(f em

al es

) A

sy m

p to

m at

ic (n

= 73

7) 62

.0 %

17 .3

% 19

.3 %

0. 3%

0. 9%

0. 2%

Su b th

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sy m

p to

m at

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(n =

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36 .5

% 35

.2 %

26 .2

% 0.

8% 1.

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ge ea

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= 32

1) 33

.5 %

22 .5

% 40

.2 %

1. 7%

2. 0%

0. 0%

T h re

sh o ld

sy m

p to

m at

ic B

in ge

E at

in g

D is

o rd

er (n

= 19

) 19

.6 %

28 .7

% 42

.4 %

0. 0%

9. 4%

0. 0%

B u lim

ia N

er vo

sa (n

= 10

) 15

.1 %

13 .4

% 63

.1 %

0. 0%

8. 4%

0. 0%

A n o re

xi a

N er

vo sa

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

0) N

/ A

(n =

N o te

: A

ll n s

ar e

w ei

gh te

d .

N / A

= n o t ap

p lic

ab le

b ec

au se

th er

e w

er e

n o

ca se

s o f A

n o re

xi a

N er

vo sa

am o n g

fe m

al es

at T im

e 1.

318

Eating Disorder Diagnostic Stability 319

indicating that adolescence is not “too late” for the implementation of interventions. The high prevalence of adolescents “progressing” from body image disturbance only to conditions involving harmful disordered eating behaviors demonstrates the importance of addressing body image concerns during adolescents. Our findings are in line with previous studies that have found body dissatisfaction to be a strong predictor of unhealthy weight control practices, binge eating, and disordered eating behaviors (Neumark- Sztainer, Wall, Story, & Perry, 2003). Furthermore, as findings from the current study suggest, many of the youth meeting criteria for a full threshold disorder at Time 2 did not have a full threshold disorder at Time 1. These findings are consistent with recent longitudinal work by Stice et al. that emphasizes the peak risk for Bulimia Nervosa and Binge Eating Disorder during mid to late adolescence (Stice et al., 2009). Thus, there is ample opportunity during this critical time in adolescent development to address concerns that might lead to the development or worsening of eating and body image disturbances. In sum, findings from the current study build upon the extant literature suggesting the importance of prevention work with adolescent populations.

Furthermore, because subthreshold classifications have been found to have similar levels of psychopathology compared to threshold diagnoses (Ackard, Fulkerson, & Neumark-Sztainer, 2011; Chamay-Weber, Narring, & Michaud, 2005; Thomas, Vartanian, & Brownell, 2009), it is critically impor- tant to detect the early development of disordered eating behaviors and body image disturbances and intervene as soon as possible to reduce the risk of maintaining subthreshold symptoms or developing a threshold eating disor- der. Future research should evaluate the associations between psychological and behavioral health and diagnostic stability, as awareness of an individ- uals’ functioning is integral to understanding and evaluating more fully the severity of a range of eating disorder diagnostic classifications (Ro & Clark, 2009).

In the current study, among the subthreshold and threshold classifica- tions, there were patterns of improvement, stability, and worsening among both males and females. In the current study, the poor stability of eating disorder diagnoses found based on current diagnostic nosology supports a call for action by Eddy and colleagues to investigate the temporal stability of diagnoses (Eddy et al., 2009). Our findings also suggest greater flexibility and less rigidity in eating disorder classifications, at least for youth, given the lack of stability between different classifications, and the associations between even subthreshold classifications and compromised psychological health are concerning (Ackard et al., 2011). Further longitudinal research, similar to that conducted here and by Stice and colleagues (Stice et al., 2009), should be conducted with male and female adolescents to evaluate the sta- bility of individual eating disorder behaviors, body image disturbances, and weight- and shape-focused experiences over time.

320 D. M. Ackard et al.

Strengths and Limitations

A significant strength of the current study is the use of data from a large, population-based sample of males and females selected to reflect socioeco- nomic diversity in urban areas of the United States. The Project EAT study was designed to look at population-based problems with a focus on the eating disorder and body image symptoms and experiences that affect a large portion of the study population, not simply on the current eating disorder clinical diagnoses. The large dataset of both males and females allowed us to investigate finer nuances in diagnostic classification than pre- vious research of general adolescent populations. Another study strength includes the comprehensive nature of the data collected, mapped to current DSM-IV diagnostic nosology and evaluated over time, and including both threshold and subthreshold diagnostic classifications.

A limitation of the present study is the small sample sizes of the AN and BN groups, which may have prohibited us from detecting meaning- ful differences between these groups and the other diagnostic groups. It is not clear whether the prevalence of conditions such as AN were truly non-existent among our population or, rather, that young people with this condition self-selected out of responding. In addition, given the compre- hensive nature of the Project EAT survey, we were not able to assess eating disorders, per se, as one would during a structured clinical interview, which would allow for an assessment of clinical impairment as well as duration and frequency of symptoms over time. Thus, the validity between our eating disorder symptom classifications and those specific to the DSM-IV diagnostic criteria are unknown. Additionally, it may be that certain cases of AN were not detected in the Project EAT study population. Finally, the Project EAT survey did not gather information on whether participants had received any early education or intervention or treatment for an eating dis- order or disordered eating concern. Some individuals previously at risk or affected by an eating disorder may have received early intervention or treat- ment before Time 1 or between Time 1 and Time 2 assessments. However, given the prevalence of adolescents who receive treatment for an eating disturbance, we believe that this reflects a very small portion of the study population.

Overall, the strengths of this study allow for a thorough discussion of the stability of subthreshold and threshold eating disorder classifications among male and female youth over a five-year period of time, and results may be generalized to samples other than those seeking or participating in treatment. However, the body of knowledge on diagnostic stability will benefit from further evaluations of both male and female youth across longer follow-up periods, and investigations of possible fluctuations in mental health con- cerns (e.g., depression, low self-esteem, suicide risk) as eating disorder classifications improve, stay stable, or worsen over time.

Eating Disorder Diagnostic Stability 321

In conclusion, this study found that there is substantial worsening of symptoms among youth over a five-year study period. Furthermore, although the majority of youth with disordered eating and body image con- cerns do not meet criteria for a full threshold eating disorder, most of the subthreshold cases remained symptomatic and a few worsened to meet a full threshold eating disorder diagnosis across the five-year study period. Our findings underscore the critical importance of early detection and early intervention during mid to late adolescence.

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