Research on eating disorders has produced a substantial base of knowledge regarding the definitions of eating disorders, their treatment, and their prevention. There are major gaps, however, in our understanding of eating disorders, especially those occurring among adolescents. Most of the research literature on eating disorders has focused on adults, and the findings may not apply to younger individuals. Thus, the research agenda for eating disorders among adolescents is large.
DEFINING EATING DISORDERS
Diagnostic Criteria for Anorexia Nervosa and Bulimia Nervosa
The DSM-IV diagnostic criteria for eating disorders are useful but imperfect. Perhaps the most glaring problem is that the current criteria do not provide a category, beyond the nonspecific eating disorder not otherwise specified, for a substantial fraction of the individuals who present to clinicians for evaluation and treatment. Eating disturbances that do not meet the full DSM-IV criteria for anorexia nervosa or bulimia ner-vosa are inadequately described, and it is unclear how clinically significant eating problems are to be differentiated from other eating pathologies, and whether individuals classified as having eating disorder not otherwise specified will develop full-blown disorders. Several promising approaches to these problems have been developed in recent years, such as the Great Ormond Street criteria (Lask & Bryant-Waugh, 2000) and the categories of the Diagnostic and Statistical Manual for Primary Care (DSM-PC), and these deserve further examination. Longitudinal examinations of the course of eating disorder symptoms during adolescence and the course of associated psychological and physical problems (e.g., obesity) would also be very valuable in defining the evolution and characteristics of adolescent eating disorders.
In adults, anorexia nervosa and bulimia nervosa affect approximately 1% and 3% of women, respectively, with rates among men estimated at one tenth of those observed in women (Hoek, 2002). The small number of methodologically rigorous epidemiological studies leads to significant uncertainty about the prevalence and incidence of anorexia nervosa and bulimia nervosa among adolescents. The peak incidence (number of new cases per year) of anorexia nervosa appears to occur in late adolescence (Hoek & van Hoeken, 2003), but the combined prevalence (number of current cases) of anorexia nervosa and bulimia nervosa appears to be somewhat less among adolescents than among adults. Methodologically rigorous studies may find that the published rates do not adequately reflect the true prevalence of eating disorders in adolescents. Epidemiological research on eating disorders among adolescents is limited in several important ways. Nationally representative samples are needed to determine more precisely how common eating disorders are among American youth. The extant (and limited) evidence suggests that ethnic minority children need to be included to gain a more accurate understanding of risk for eating disorders in non-white youth.
The epidemiological literature has, for the most part, used clearly articulated diagnostic criteria for anorexia nervosa and bulimia nervosa, and the difficulties in defining the spectrum of other eating disturbances have presented a significant barrier to describing the prevalence of other potentially important but less well–defined conditions. For example, future studies should include criteria for binge eating disorder to permit estimates of the prevalence of this syndrome. A uniform instrument for measuring eating disorder symptoms that is efficient and accurate in detecting anorexia nervosa, bulimia nervosa, and binge eating disorder and is standardized across studies would be of great value. Psychiatric interviews that “skip out” of the eating disorder questions after a negative answer may underestimate eating pathology, especially in young samples with atypical clinical presentations of anorexia nervosa or bulimia nervosa (Kreipe et al., 1995). Finally, parent reports of eating behavior might improve the detection of anorexia nervosa, a disorder in which denial is a hallmark.
Future studies should assess both current and past eating disorders. Several population-based studies have shown that eating disorders may be transient (albeit in many cases recurrent) and point prevalence rates may therefore not fully reflect the extent of eating pathology in adolescents (Patton, Coffey, & Sawyer, 2003). Even when the adolescent's eating disorder is time limited and nonrecurring, it may represent a marker for psychopathology that conveys important clinical information.
Comorbidity, Outcome, and Migration
Psychiatric comorbidities are common among both adolescents and adults with anorexia nervosa and bulimia nervosa, and include mood disorders, anxiety disorders, and substance use disorders. However, the relationship between anorexia nervosa, bulimia nervosa, and comorbid disorders is unclear. The outcome of adolescent patients with anorexia nervosa who receive early treatment appears better than that of patients who do not; however, those patients who remain ill have high rates of psychiatric comorbidity and are at risk for premature death. Most adolescent anorexia nervosa patients improve or get well, but a substantial percentage remains permanently symptomatic. The data on the course and outcome of adolescent bulimia nervosa are very limited. Diagnostic migration occurs frequently from anorexia nervosa-restricting subtype (AN-R) to anorexia nervosa-binge purge subtype (AN-B/P), and from AN-B/P to bulimia nervosa. It is currently not possible to identify those patients likely to migrate.
Future studies of adolescents with eating disorders should include individuals with comorbidities, such as substance use disorders, to aid in developing treatment strategies for these dual-diagnosis conditions. Studies of the course and outcome of adolescent bulimia nervosa are needed, and early identification and intervention strategies need to be developed.
While most medical complications associated with eating disorders are reversible with nutritional rehabilitation and cessation of the binge–purge cycle, there are indications that growth retardation, osteopenia, and, possibly, structural brain changes are not entirely reversible. Studies probing structural brain changes in anorexia nervosa and their relationship to neuropsychological changes are needed. In addition, there is a pressing need to develop efficacious treatments for osteopenia among adolescents with anorexia nervosa.
TREATMENTS FOR EATING DISORDERS
Arguably, the most compelling need for future research is to develop effective treatments for adolescents with eating disorders. A significant body of information is available on interventions for adults with bulimia nervosa, and there are promising developments in the treatment of adolescents with anorexia nervosa. It is imperative to build on these initial efforts.
Psychological Treatment of Anorexia Nervosa
There is only one evidence-based treatment for adolescents with anorexia nervosa, the Mauds-ley method of family therapy, whether delivered in a conjoint or separated format. The empirical evidence supporting the treatment is limited, however. Whereas a subgroup of anorexia nervosa patients may have an inherently good prognosis, it is clear that significant numbers of these patients do not do well. For example, Eisler et al. (2000) found in their study (in which all the patients received the Maudsley method of family therapy) that 15 of 40 patients were judged to have a “poor” outcome on the Morgan-Russell scales and 4 patients had to be admitted to the hospital because of continuing weight loss. At the end of the study by Robin et al. (1999), the authors note that “even with comprehensive, multidisciplinary interventions such as those evaluated in this study, not all adolescents with anorexia nervosa will improve. Twenty to 30 percent of the patients did not reach their target weights, and 40% to 50% did not reach the 50th percentile of BMI by 1-year follow-up. Clinicians and researchers will need to continue to develop innovative approaches to helping these more resistant patients” (p. 1489).
A potentially promising treatment for adolescent anorexia nervosa patients is cognitive-behavioral therapy (CBT). This therapy is the leading evidence-based treatment for bulimia nervosa (National Institute for Clinical Excellence, 2004; Wilson & Fairburn, 2002), a disorder that has much of the same psychopathology as that of anorexia nervosa (Fairburn & Harrison, 2003; Fairburn, Cooper, & Shafran, 2003). Additionally, CBT is already used with adults with anorexia nervosa (e.g., Garner, Vitousek, & Pike, 1997), and a recent cognitive-behavioral conceptualization of anorexia nervosa may pertain to adolescent patients, given its emphasis on the early stages in the evolution of the disorder (Fairburn, Shafran, & Cooper, 1999). Finally, CBT has been successfully used to treat other psychiatric disorders in adolescence (Kazdin, 2003; Kendall, 2000).
If CBT were to be developed as a treatment for these patients, it would need to be adapted in certain ways. It would need to be based on a model of the maintenance of anorexia nervosa, focusing on the processes involved in recent-onset cases (e.g., Fairburn, Shafran, et al., 1999). The therapy would need to take account of the developmental psychology of adolescence and the specific concerns of adolescents, and it would need to be adjusted to accommodate the developmental variability seen among adolescents (Holmbeck et al., 2000; Weisz & Hawley, 2002). It would also need to involve the patient's family and possibly the school.
A challenging issue in the study of new treatments for anorexia nervosa is the choice of the comparison, or “control,” treatment. In theory, it might be useful to compare the effect of a new intervention with that of no treatment at all or a waiting-list condition. While such a comparison neatly controls for the effect of time alone, it is difficult to justify a delay of treatment for individuals with a disorder having such serious medical and psychiatric morbidity. Furthermore, documentation that a new treatment is superior to doing nothing does not provide strong evidence of specific clinical utility. A comparison between two interventions likely to be useful (e.g., the Maudsley method and suitably adapted CBT) may be difficult to interpret without controls for the effect of time and for the nonspecific effects provided by any intervention. The notion of a “treatment-as-usual” comparison group has appeal, but the definition and implementation of such an intervention in the context of a research study are far from clear.
Psychological Treatment of Bulimia Nervosa
Controlled trials are needed to identify and evaluate the efficacy of psychological treatments for adolescents with bulimia nervosa. Both CBT and interpersonal psychotherapy (IPT) have been shown to be effective for adult bulimia nervosa patients. These treatments should be adapted and applied to adolescents, because CBT and IPT have been successfully adapted to treating adolescents with other problems. The case is particularly compelling for CBT, as it is the treatment of choice for bulimia nervosa in adults, its adaptation to depressed and anxious adolescents has received the most study and enjoys the most empirical support, and it meshes well with the generic and specific considerations governing psychological treatment of adolescents.
Alternative psychological therapies should also be explored. An adaptation of the family-based treatment developed by Lock, Le Grange, Agras, and Dare (2001) is an obvious candidate for study, given its apparent efficacy with adolescent anorexia nervosa. Research is also needed to assess the comparative efficacy of evidence-based psychological treatments, such as CBT, IPT, or family therapy, with antidepressant medication and their combination (sequencing).
Pharmacological Treatments for Eating Disorders
Few controlled studies have evaluated the utility and safety of pharmacological treatments for adolescents with eating disorders, although medications are frequently used in the clinical treatment of these patients. Antidepressant medications have demonstrated efficacy in reducing binge eating and vomiting behaviors for adults with bulimia nervosa, but additional study will be necessary before any conclusions can be reached about the use of these medications with younger patients. There is currently no evidence for the efficacy of pharmacological treatments in low-weight adults with anorexia nervosa. However, recent reports have suggested a utility of atypical antipsychotic medications, such as olanzapine, with adolescent anorexia nervosa patients, and future research should evaluate these medications in a controlled manner.
For both adolescents and adults with anorexia nervosa, the risk of posthospitalization relapse is approximately 30%–50%. The Maudsley form of family therapy appears to have efficacy for preventing relapse among adolescent anorexia nervosa patients, but family therapy may be most effective for patients who develop anorexia nervosa before age 18 and who have less than 3 years duration of illness. Although there are no data on the efficacy of CBT for relapse prevention among adolescents, this treatment has support for relapse prevention in adult patients. A single controlled study in adults suggests that antidepressant medication may reduce the rate of relapse following weight restoration, but there are no data on the utility of this intervention to prevent relapse among adolescents.
Adolescents with bulimia nervosa have not been the focus of clinical treatment trials, and studies that include adolescent patients are not sufficient to draw conclusions about relapse prevention for these patients. Little is known about the efficacy of psychological or pharmacological treatments for adolescents with bulimia nervosa, both for the acute treatment of the disorder and the prevention of relapse.
Methodological and logistical challenges hamper progress in the development of effective relapse prevention interventions. Operationalized and consistent definitions of treatment response, relapse, remission, and recovery, and a standardized assessment battery would enhance the study of both initial interventions and relapse prevention. Clinical trials require tremendous resources, and the failure to develop consensus in the field on core terminology and assessment procedures will continue to hinder development of empirically supported treatments. Discussions of relapse and relapse prevention lead to dichotomous distinctions: either an individual has responded to treatment or not; either an individual has relapsed or not. In reality, change in clinical status is continuous, which complicates the establishment of thresholds and standardized classifications. Several authors have attempted to address this important issue (Orimoto & Vitousek, 1992; Pike, 1998).
Intensive but expensive initial treatments for anorexia nervosa, such as inpatient or partial hospitalization, are arguably the most successful in achieving weight restoration, especially among severely and chronically ill patients. Weight restoration is an essential goal in achieving recovery and is the first step in preventing relapse. However, economic pressures on reducing health-care expenditures, at least in the United States, are limiting patients' ability to receive sufficient care to achieve weight restoration. Studies of the short-and long-term costs and benefits of interventions of a range of intensity would be extremely valuable in helping to define which treatments are most cost-effective.
Treatments for Adolescents: Summary
The encouraging work on the utility of the Maudsley method for adolescents with anorexia nervosa should be pursued in studies comparing this intervention to other standard and novel approaches. Empirically supported psychological treatments for adults with eating disorders, including CBT and IPT, should be adapted to the treatment of adolescents. This process should include collaboration between treatment researchers and developmental psychologists who study adolescence. Treatments should be designed to address issues specific to adolescent patients, including motivation, cognitive processing, interpersonal functioning, body image, control, and family issues. The utility and safety of psychopharmacological interventions for adolescents with eating disorders are in need of critical examination, as such agents are commonly employed despite the current absence of evidence of efficacy.
Because eating disorders are uncommon, multisite studies will be necessary for the definitive examination of treatment efficacy and of relapse prevention. Multisite studies will further support initiatives to establish standards for terminology and assessment, as standardization is required for the execution of such trials. Another significant advantage of multisite studies is that the enhanced power will provide the opportunity to conduct more specific investigations of the relationship between eating disorder subtype, comorbidity, treatment response, and relapse.
In addition, novel approaches to study design and procedures in the treatment of adolescents with eating disorders should be considered not only for developmental considerations in treating younger patients but also because many eating disorder research centers serve as secondary and tertiary referral centers and therefore do not currently treat significant numbers of younger, new-onset cases. The particular ethical considerations and the reluctance of parents to have their children participate in clinical research are also critical issues that need to be addressed to increase clinical research initiatives focused on adolescents with eating disorders.
PREVENTION OF THE DISORDER
Risk Factors for Anorexia Nervosa
While there have been numerous studies to identify risk factors for the development of anorexia nervosa, few true risk or protective factors for the development of anorexia nervosa have been definitively established. Population-based longitudinal databases, which include prospectively collected data on large populations that include incident cases, may shed light on questions of etiological relevance to anorexia nervosa. Such projects must be viewed as a priority. Research on the risk factors for anorexia nervosa must be appropriately divided between biological–genetic and environmental factors. Because anorexia nervosa is influenced by both biological and environmental factors, a comprehensive exploration of gene and environment interactions may provide valuable information about the etiology of this disorder.
Risk Factors for Bulimia Nervosa
Factors such as perceived pressure to be thin, thin-ideal internalization, body dissatisfaction, and negative affect have been identified as risk factors for the development of bulimia nervosa. Future research should be directed at identifying new risk factors for bulimia nervosa, as most of the established risk factors have relatively modest effect sizes (Stice, 2002). Promising variables include hypersensitivity to negative interpersonal transactions, cognitive factors (e.g., affect regulation expectancies), feeding avidity, and individual differences in reinforcement from eating. In addition, the role of dieting in the development of bulimic pathology should be clarified.
Research should also begin to examine potential biological risk factors for bulimic pathology (e.g., serotonin abnormalities and structural differences in the orbitofrontal cortex); research has yet to identify a single biological risk factor for bulimic pathology. Furthermore, studies should continue to search for genetic factors that influence risk for this eating disorder.
Relatively little is known about the ways in which risk factors work together to promote the development of this disorder or about possibly distinct etiologic pathways in bulimia nervosa. Thus future research should test multivariate models to determine how the various risk factors work in concert to promote bulimic pathology. It will be particularly important to focus greater attention on identifying protective and potentiating factors and on the means by which psychosocial and biological factors work together to foster bulimic pathology.
Research should also investigate whether the risk factors for symptom onset differ from those for symptom escalation and maintenance. This is important because the former are germane to the design of universal and selected prevention programs, but the latter are necessary for the design of optimally effective indicated prevention programs and treatment interventions.
More generally, the use of prospective and experimental designs should be encouraged. These research methods are potentially powerful means of elucidating the etiologic processes that give rise to eating disorders.
Treatment of Obesity as a Risk Factor for Eating Disorders
Research on professionally administered weight loss programs for overweight children and adolescents indicates that these programs do not appear to increase symptoms of eating disorders. Conclusions about the relationship between the treatment of obesity and eating disorders are based on a very limited number of studies, and further research is needed before firm conclusions can be reached. In particular, studies are needed to reconcile findings of the apparently benign effects of dieting, as practiced in behavioral weight loss programs, to determine whether dieting precipitates eating disorders. Several issues must be considered.
First, healthy dieting, which encourages only modest caloric restriction, in combination with increased consumption of low-fat dairy products and fruits and vegetables, appears to present few risks to overweight youth. As previously mentioned, this type of dieting is likely to improve the nutritional value of foods consumed. By contrast, unhealthy weight loss behaviors, which include severe caloric restriction (e.g., crash diets) and the prohibition of certain foods (e.g., fad diets), could significantly increase the risk of eating disorders and emotional complications. This is possible in overweight youth, as well as in normal-weight girls who diet aggressively in pursuit of an ever-thinner ideal. Similarly, chronic restrained eating may pose risks that are not associated with healthy dieting.
Second, disturbances in eating behavior and mood must be clearly defined and measured. The pediatric obesity studies reviewed in this volume did not assess criteria for the diagnosis of bulimia nervosa, binge eating disorder, or eating disorder not otherwise specified. None, for example, measured objective or subjective binge episodes, as defined by Fairburn and Cooper (1993). Future studies could incorporate efforts to modify the Eating Disorder Examination (Fairburn & Cooper, 1993) for use with children and adolescents (Bryant-Waugh, Cooper, Taylor, and Lask, 1996).
Third, some overweight youth may be at greater risk for adverse behavioral consequences of dieting and weight loss, even when they participate in a professionally administered program. Longitudinal studies, for example, have shown that severe body image dissatisfaction and weight and shape preoccupation are the most robust predictors of the development of eating disorders in adolescent girls. Thus, overweight teenagers with marked body image dissatisfaction, depression, or other psychiatric complications may be at greatest risk of experiencing binge eating episodes when subjected to even modest caloric restriction, and research in this area is needed.
Finally, weight regain is common in overweight adolescents, as in obese adults. Studies of adults have not found weight cycling (i.e., weight loss followed by regain) to be associated with clinically significant behavioral consequences; however, in overweight youth with a history of psychiatric complications, weight cycling might produce different effects. Whenever possible, follow-up assessment should be conducted through late adolescence when symptoms of bulimia nervosa or binge eating disorder might emerge.
Ultimately, large-scale randomized controlled trials will be needed to determine the behavioral risks posed by different weight loss interventions for overweight youth. Ethical constraints will limit investigators from using such trials to assess the effects of crash diets and other fundamentally unsound approaches. In addition, given the generally low occurrence of eating disorders, case–control studies may provide a better mechanism of identifying dietary practices most likely to be associated with adverse behavioral effects. Health professionals, teachers, and parents will continue to be concerned about misguided weight loss efforts in children and teenagers, but all should be increasingly concerned about the growing epidemic of pediatric obesity. Fifteen percent of America's adolescents are already overweight and as adults will experience serious medical and psychosocial consequences of this condition. Concerns about potential ill effects of dieting should not impede efforts to improve the treatment of pediatric obesity. More important, such concerns should not discourage urgently needed efforts to prevent the development of overweight in both children and adults.
Eating Disorder Prevention Research
Prevention research is an important issue in eating disorder research, even though the impact of eating disorder prevention programs for children and adolescents is not clear (Pratt & Woolfenden, 2002). Future research should include longitudinal studies of universal prevention with an integrated, multidimensional, and systemic approach to schools and other important parts of the community. These studies should demonstrate significant reductions in risk factors and a reduction in incidence of the disorders. In addition, studies of targeted interventions are needed to focus on valid and ethical ways to identify individuals and environments that are at-risk and provide interventions that reduce risk factors and incidence of the disorders. Research should demonstrate that significant and important changes in the putative risk factors or protective factors can be achieved and maintained.