REVIEW Reducing Eating Disorder Symptoms and Risk Factors Using the Internet: A Meta-Analytic Review Tiffany Melioli, MA1 * Stephanie Bauer, PhD2 Debra L. Franko, PhD3 Markus Moessner, PhD2 Fikret Ozer, MA2 Henri Chabrol, MD, PhD1 Rachel F. Rodgers, PhD3,4 ABSTRACT Objective: The purpose of this metaanalytic review was, first, to evaluate the efficacy of Internet-based programs in decreasing eating disorder (ED) symptoms, and, second, to identify moderator variables these effects. Method: Twenty studies were identified and between-group effect sizes were calculated for ED symptoms and risk factors. Results: Compared with control conditions, Internet-based programs successfully decreased body dissatisfaction (d 5 0.28, 95% CI [0.15–0.41], p < .001), internalization of the thin ideal (d 5 0.36, 95% CI [0.07–0.65], p < .05), shape and weight concern (d 5 0.42, 95% CI [0.13–0.71], p < .05), dietary restriction (d 5 0.36, 95% CI [0.23–0.49], p < .001), drive for thinness (d 5 0.47, 95% CI [0.33–0.60], p < .001), bulimic symptoms (d 5 0.31, 95% CI [0.20–0.41], p < .001), purging frequency (d 5 0.30, 95% CI [0.02–0.57], p < .05), and negative affect (d 5 0.32, 95% CI [0.12–0.52], p < .001). Moderator analyses revealed no impact of data analytic strategy on intervention effects. Similarly, participant risk status was not a moderator for most outcomes. Discussion: Internet-based programs are successful in decreasing ED symptoms and risk factors with small to moderate between-group effect sizes. Keywords: eating disorders; intervention; prevention; internet; risk factors; moderator Resumen Objetivo: El proposito de esta revision meta-analıtica fue, primeramente, evaluar la eficacia de los programas basados en internet para disminuir los sıntomas de trastorno de la conducta alimentaria (TCA), y segundo, identificar variables moderadoras de estos efectos. Metodo: Se identificaron veinte estudios y se calculo el tama~no del efecto entre grupos para los sıntomas de TCA y los factores de riesgo. Resultados: En comparacion con las condiciones de control, los programas basados en Internet redujeron con exito la insatisfaccion corporal (d 5 0,28; IC del 95% [0,15-0,41], p <0,001), interiorizacion del ideal de delgadez (d 5 0.36, 95% CI [0,07 hasta 0,65], p <0,05), la preocupacion por el peso y la figura (d 5 0,42; IC del 95% [0,13 a 0,71], p <0,05), la restriccion dietetica (d 5 0,36; IC del 95% [0,23 a 0,49], p <0,001), la busqueda de la delgadez (d 5 0,47; IC del 95% [0,33 a 0,60], p <0,001), los sıntomas bulımicos (d 5. 31; IC del 95% [0,20-0,41], p <0,001), la frecuencia de purgacion (d 5 0,30 IC del 95% [,02-,57], p <0,05) y el afecto negativo (d 5. 32; IC del 95% [0,12 hasta 0,52], p <0,001). Los analisis moderador no revelaron ningun impacto de la estrategia analıtica de datos sobre los efectos de intervencion. Del mismo modo, el estado de riesgo de los participantes no fue un moderador para la mayorıa de los resultados. Discusion: Los programas basados en Internet tienen exito en la reduccion de los sıntomas de TCA y los factores de riesgo con un tama~no de efecto peque~no a moderado entre grupos. VC 2015 Wiley Periodicals, Inc. (Int J Eat Disord 2016; 49:19–31). Accepted 1 October 2015 *Correspondence to: Tiffany Melioli, Octogone-Centre d’etude et de recherche en psychopathologie, Universite Toulouse II, 5 Allees Antonio Machado, 31058 Toulouse cedex 9, France. E-mail: tiffany.melioli@gmail.com 1 Octogone-Centre D’etude Et De Recherche En Psychopathologie, Universite Toulouse II, 5 Allee Antonio Machado, 31058, Toulouse Cedex 9, France 2 Center for Psychotherapy Research, University Hospital Heidelberg, Bergheimerstr. 54, Heidelberg, 69115, Germany 3 Department of Counseling and Applied Educational Psychology, Northeastern University, Boston, Massachusetts 4 Laboratoire Du Stress Traumatique (EA 4560), Universite Toulouse-III Paul Sabatier, Toulouse, 31400, France Published online 26 November 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/eat.22477 VC 2015 Wiley Periodicals, Inc. International Journal of Eating Disorders 49:1 19–31 2016 19 Introduction Eating disorders (EDs), including subthreshold forms, are increasingly common, and among the most severe of mental disorders.1–3 Successful prevention and treatment programs for young women have been developed4–8 ; however, these face-toface interventions present a number of limitations, and are costly and difficult to disseminate, leading to calls capitalize on the possibilities offered by the Internet.6,9 The Internet may have great potential for enhancing the treatment and prevention of EDs due to advantages in accessibility, cost, and ease of dissemination.6,10 Internet-based psychotherapeutic intervention programs have been suggested to offer specific advantages for EDs.11–13 Although the number of Internet-based programs has multiplied, their success in decreasing ED symptoms is still unclear. Because of the potential advantages of Internet-delivered programs, establishing their efficacy is an important step toward greater dissemination.12,14,15 Existing Internet-based ED intervention programs have been identified in two systematic reviews,11,16 which have reported encouraging findings, concluding that Internet-based programs are emerging as a successful approach for the treatment of ED symptomatology. The efficacy of ED prevention programs delivered exclusively through the Internet (as opposed to other forms of technology) has been explored through two meta-analy- ses.17,18 The first found little evidence for their efficacy,18 whereas the second documented moderate improvements in ED symptoms.17 As both of these reviews focused on the same prevention program (Student Bodies), the difference might stem from the fact that the second was far more inclusive and might have greater statistical power17 than the first one.18 A third meta-analysis has explored the efficacy of technology-based intervention and both selective and universal prevention programs and provided an overview of e-therapy delivered through computers, CD-Rom, the Internet, or mobile-device applications.19 The authors concluded that the efficacy of such programs should be considered with caution and that further research was needed. Although these three meta-analyses have explored the efficacy of ED Internet-based programs,17–19 their findings are limited by the lack of focus on variables that might account for the efficacy of Internet-based programs. To our knowledge, only one meta-analysis has reported exploratory moderator analyses.17 Moderator analyses were performed on weight concern outcomes to evaluate the efficacy of the Student Bodies program between U.S. versus German samples and universal versus selective prevention samples. The authors reported heterogeneity on the Weight and Shape Concern Scale (WCS) and suggested differences on weight concern outcomes depending on country and risk status. Regarding individual studies, moderators of intervention effects have been identified in two studies,20,21 with the greatest effects found among participants with high BMI and compensatory behaviors at baseline20 and the lowest effects found among participants with FIGURE 1. Sample search strategy for PsycInfo. MELIOLI ET AL. 20 International Journal of Eating Disorders 49:1 19–31 2016 high purge behaviors and restrictive eating at base- line.21 Exploring the impact of risk status on effects across a larger number of interventions would increase our understanding of the impact of initial symptomatology on intervention effects. While face-to-face selected prevention programs have been found to result in greater decreases in ED symptoms compared with universal prevention, little is known regarding the potential moderators of their effects. Given the lack of consensus between previous meta-analyses regarding the efficacy of ED Internet-based programs, conducting a meta-analysis incorporating all studies published to date in symptomatic individuals (selective prevention) and those meeting diagnostic criteria (intervention) might help clarify previous results.17–19 Moreover, it will be useful to clinicians to provide a clearer picture of the efficacy of Internet-based programs in reducing ED symptoms along a continuum of severity. Furthermore, to our knowledge, to date, little is known regarding the influence of potential moderator variables on the efficacy of Internet-based programs. Thus, the aim of this meta-analytic review was twofold: first, to evaluate the efficacy of Internet-based programs in decreasing ED-related risk symptoms among symptomatic individuals as well those with diagnosed ED; second, to identify moderator variables of these effects. Method The literature review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines.22 Eligibility Criteria We included studies that (1) were published in English between January 2000 and January 2015; (2) used experimental or quasi-experimental study designs with a waitlist condition or another type of control group with a minimal intervention such as a brochure (studies with an active control group such as bibliotherapy or comparing face-to-face and Internet-based programs were excluded); (3) included symptomatic participants or FIGURE 2. Study selection process. REDUCING ED SYMPTOMS USING THE INTERNET International Journal of Eating Disorders 49:1 19–31 2016 21 participants with full EDs; (4) provided measures of EDrelated symptoms; and (5) provided sufficient data to compute between-group effect sizes. Programs that screened for or used advertisements designed to select symptomatic individuals were considered to be selective prevention programs.7 Studies that included individuals with an ED diagnosis based on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria were identified as intervention programs. Information Sources and Search Strategy A literature search (Fig. 1) was conducted via PubMed, PsychINFO, Science Direct, and Google Scholar, using the criteria: Language (English), date (2000–2015), and published studies. An ancestry approach was used to complete computer searches.23 Keywords were “Disordered Eating” and “Internet Intervention”; “EDs” and “Internet Prevention”; “Anorexia” and “Internet Intervention”; “Bulimia” and “Internet Intervention.” TABLE 1. PICOS (participants, intervention, comparison, outcome, study design) characteristics in identified studies Study Participants, Mage (SD) Intervention Comparisons Outcomes Design Type of Control Group Winzelberg et al.29a–c Women students with desire to improve body image satisfaction 20.0 (2.8) IBPP: SB Web-based group (n 5 31); control (n 5 29) BSQ, EDI-DT, EDI-BN, EDE-Q NR WLC Celio et al.30a–c Women with high BD 19.6 (2.2) IBPP: SB Web-based group (n 5 27); control (n 5 24) EDE-Q, BSQ, EDI-DT, EDI-BN R WLC Zabinski et al.31a–c Women students with body shape concern 19.3 (1.4) IBPP: SB Web-based group (n 5 31); control (n 5 31) BSQ, EDI-DT, EDI-BN, EDE-Q R WLC Zabinski et al.32 Women students at risk for developing an ED 18.9 (2.4) IBPP Web-based group (n 5 28); control (n 5 30) EDE-Q R WLC Taylor et al.20b,c Women with high weight and shape concern 20.8 (2.6) IBPP: SB Web-based group (n 5 192); control (n 5 199) WCS, EDI-DT, EDI-BN, EDE-Q, CES-D R WLC Low et al.33b,c Women students with desire to improve body image IBBP:SB Web-based group (n 5 14); control (n 5 14) EDI-DT, EDI-BN, EDIBD, WSC; SATAQ R WLC Heinicke et al.34 Adolescent girls selfidentifying as having body image or eating problems 14.4 (1.5) IBPP: My body, my life Web-based group (n 5 40); control (n 5 43) BSQ, BCS, DEBQ-R, EWLB, EDI-BN, SATAQ-3, BDISF R WLC Paxton et al.35 Women with high BD 25.6 (5.8) IBPP Web-based group (n 5 37); control (n 5 37) BSQ, PACS, BULIT-R, DEBQ-R, BDI-II R WLC Jacobi et al.36b,c Women students who wanted to improve their body image 22.5 (2.7) IBPP: SB Web-based group (n 5 47); control (n 5 50) EDI-DT, EDI-BN WCS, EDE-Q R WLC Doyle et al.37c Overweight or at risk for overweight adolescents 14.5 (1.7) IBPP: SB2 Web-based group (n 5 40); control (n 5 40) EDE-Q R TAU Jones et al.38c,d Adolescent at risk for overweight 15.1 (1.0) IBPP: SB 2 Web-based group (n 5 52); control (n 5 53) EBI, CES-D R WLC Fernandez-Aranda et al.39d,e Women with BN 23.7 (3.6) IBIP Web-based group (n 5 31); control (n 5 31) EDI, EAT-40, BITE NR WLC Sanchez-Ortiz et al.40c–e Women students with BN or EDNOS 23.9 (5.9) IBIP Web-based group (n 5 38); control (n 5 38) EDE-Q R WLC Carrard et al.41c–e Women with full or subthreshold BED 36 (11.4) IBIP Web-based group (n 5 37); control (n 5 37) EDE-Q, EDI-DT, EDIBN, EDI-BD, T-FEQ R WLC Carrard et al.42d,e Obese women and men with BED 42.8 (9.8) IBIP Web-based group (n 5 22); control (n 5 20) EDO, EDE-Q, TFEQ NR WLC Fichter et al.43c Women with full or subthreshold AN 24.1 (5.6) IBPP Web-based group (n 5 106); control (n 5 113) EDI R TAU Jacobi et al.44c,d Women with subthreshold ED 22.3 (2.9) IBPP: SB1 Web-based group (n 5 51); control (n 5 52) EDE-Q, WCS, EDI-DT, EDI-BN, EDI-BD, BDI R WLC MELIOLI ET AL. 22 International Journal of Eating Disorders 49:1 19–31 2016 Study Selection and Data Collection Process Data were collected by the first author (Fig. 2). The data collection form contained the following items: literature (authors, date, title), program (intervention vs. prevention), participants (N, Mage, standard deviation [SD], gender), outcomes, and study design (randomized or non-randomized). Risk of Bias in Individual Studies Quality assessment and data extraction were conducted by the first author. All studies screened were published in English. Data Analysis Statistical heterogeneity across studies was determined using the Q-test for heterogeneity (substantial heterogeneity when p < .1024 ) and the I2 statistic (unimportant to moderate heterogeneity when I2 < 50%, and substantial when I2 > 50%25 ). We calculated summary between-group effect sizes for studies testing the effects of Internet programs against a control group. Potential outliers for each outcome were identified using standardized residuals with 1.96 as a cut-off.26 Betweengroup effect sizes were interpreted using Cohen’s guidelines27 with 0.20 representing a small effect size, 0.50 a medium effect size, and 0.80 a large effect size. Given the small sample size in some studies, Hedges’ g was also calculated for all outcomes as this coefficient provides a better estimation in such cases.28 Analyses of moderation were conducted to explore the effect of ED symptom severity at baseline (nonclinical/mixed vs. high-risk samples) and data analysis method (intent-to-treat [ITT] vs. completers]. Studies that TABLE 1. Continued Study Participants, Mage (SD) Intervention Comparisons Outcomes Design Type of Control Group Stice et al.45c Women students with BD 21.6 (6.6) IBPP Web-based group (n 5 19); control (n 5 39) DRES, SDBPS, IBSR, BDI R BC H€otzel et al.46c Women with AN or BN symptoms 27.1 (7.8) IBPP Web-based group (n 5 49); control (n 5 76) EDE-Q, SEED R WLC Ruwaard et al.47c–e Women with BN symptoms 31 (10) IBPP Web-based group (n 5 35); control (n 5 35) EDE-Q, BAT R WLC Notes: ED, Eating Disorders; BED, Binge Eating Disorder; BN, Bulimia; BD, Body Dissatisfaction; EDNOS, Eating Disorder Not Otherwise Specified; IBPP, Internet-Based Prevention Program; IBIP, Internet-Based Intervention Program; SB, Student Bodies; R, Randomized; NR, No Randomized; WLC, Waiting-List Condition; TAU, Treatment As Usual; BC, Brochure Condition; BSQ, Body Shape Questionnaire48 ; EDI, Eating Disorders Inventory (DT, Drive for Thinness; BN, Bulimia; BD, Body Dissatisfaction)49 ; EDE-Q, Eating Disorder Examination-Questionnaire50 ; WCS, Weight and Shape Concern Scale51; SATAQ, Sociocultural Attitudes Toward Appearance Questionnaire52 ; PACS, Physical Appearance Comparison Scale53 ; BULIT-R, Bulimia Test-Revised54 ; DRES Dutch Restrained Eating Scale, DEBQ-R, Dutch Eating Behavior Questionnaire-Restraint Subscale55; BCS, Body Comparison Scale56 ; EWLB, Extreme Weight Loss Behaviors Scale57 ; EDDS, Eating Disorder Diagnostic Scale58 ; IBSS-R, The Ideal-Body Stereotype Scale-Revised59 ; MBSRQ, Multidimensional Body Self-Relations Questionnaire60 ; BES, Body Esteem Scale61 ; T-FEQ, Three-Factor Eating Questionnaire Symptom Checklist-90-Revised62 ; EDO, Eating Disorders in Obesity63 ; BAT, Body Attitude Test64 ; EAT-40, Eating Attitudes Test65 ; BITE, Bulimic Investigatory Test Edinburgh66 ; SEED, Short Evaluation of Eating Disorders67 ; SDBPS, Satisfaction and Dissatisfaction with Body Parts Scale68 ; EBI, Eating Behaviors Inventory69 ; BDISF, Beck Depression Inventory short form70 ; BDI, Beck Depression Inventory71 ; CES-D, Center for Epidemiologic Studies Depression Scale72 ; BDI-II, Beck Depression Inventory-Second Edition73 ; PANAS-X, Positive Affect and Negative Affect Scale-Revised Form.74 a Studies identified by Newton and Ciliska.18 b Studies identified by Beintner et al.17 c Studies identified by Loucas et al.19 d Studies identified by Aardoom et al.11 e Studies identified by D€olemeyer et al.16 TABLE 2. Methodological quality in identified studies Study Randomization ITT Analysis Dropout < 15% Score Winzelberg et al.29 No No Yes (13%) 1 Celio et al.30 Yes No No (23%) 1 Zabinski et al.31 Yes No Yes (2%) 2 Zabinski et al.32 Yes Yes Yes (2%) 3 Taylor et al.20 Yes No No (16%) 1 Low et al.33 Yes Yes Yes (6%) 3 Paxton et al.35 Yes Yes No (26%) 2 Heinicke et al.34 Yes Yes No (22%) 2 Jacobi et al.36 Yes No Yes (3%) 2 Doyle et al.37 Yes Yes No (20%) 2 Jones et al.38 Yes Yes No (17%) 2 Fernandez-Aranda et al.39 No No No (35%) 0 Sanchez-Ortiz et al.40 Yes Yes No (21%) 2 Carrard et al.41 Yes Yes No (17%) 2 Carrard et al.42 No No Yes (9%) 1 Fichter et al.43 Yes Yes Yes (6%) 3 Jacobi et al.44 Yes Yes No (18%) 2 Stice et al.45 Yes No Yes (2%) 2 H€otzel et al.46 Yes Yes No (41%) 2 Ruwaard et al.47 Yes Yes No (26%) 2 Notes: Quality scores range from 0 5 high risk of bias to 3 5 low risk of bias. ITT 5 intention to treat. REDUCING ED SYMPTOMS USING THE INTERNET International Journal of Eating Disorders 49:1 19–31 2016 23 included symptomatic individuals were categorized as nonclinical/mixed and studies that included participants with ED diagnoses were classed as high risk. Nonclinical/mixed- and high-risk samples are presented in Table 1 as IBPP (Internet-Based Prevention Program) and IBIP (Internet-Based Intervention Program), respectively. The analyses were conducted using Comprehensive Meta-Analysis.26 Effect sizes were calculated with preand post-mean and SD information; follow-up data were not used. We calculated overall between-group effect sizes for outcomes assessing symptoms or risk factors of EDs: body dissatisfaction,48,49,68 thin-ideal internaliza- tion,52,59 shape and weight concern,50,51,61,69 dietary restriction,50,55 drive for thinness,49 bulimic symptoms and purging frequency,49,50,54,75 and negative affect.70–74 A random effects model was used to calculate betweengroup effect size. Moderator analyses were conducted by calculating effect sizes within each group (without pooling within-group estimates of heterogeneity) and effect sizes were then compared. Results Study Selection and Study Characteristics The search strategy led to an initial pool of 590 articles of which 20 were eligible and included (Table 1). Study sample sizes ranged from 28 to 391 and mean age was 23.33 years (SD 5 7.13). Among the 20 identified studies, 4 were categorized as IBIP and 16 as IBPP. Seventeen of the 20 studies were randomized controlled studies. Among the 20 studies identified, 19 were based on cognitivebehavioral therapy principles (e.g., associations between thoughts, feelings, and behaviors) and 1 study46 was based on motivational interviewing (i.e., motivational enhancement therapy). A flow diagram with reasons for exclusions is displayed in Figure 2. Study Quality and Risk of Bias The Cochrane collaboration’s risk of bias tool was adapted to identify risk of bias.25 Thus, three criteria were used to assess study quality and risk of bias: (1) “sequence generation” through randomization; (2) “incomplete outcome data” through ITT analysis; and (3) “other bias” through dropout rates. Among the 20 identified studies, 17 included randomization, 12 were based on ITT, and 8 had a dropout rate below 15% (dropout rates varied between 2% and 41%). The methodological quality of included studies is summarized in Table 2. Studies were assessed according to each of the three criteria, and a score of 1 was attributed when the study presented methodological strengths (randomization, ITT, or dropout rate< 15%). Thus, total study quality scores ranged from 0 (presence of the three sources of bias) to 3 (high quality, absence of bias). The methodological criteria of ITT and dropout rates by condition are displayed in Table 3. Among the 20 controlled studies identified, 12 conducted ITT analyses. Five methods of ITT analyses were identified: “baseline-observationcarried-forward method” (BOCF; n5 7), “lastobservation-carried-forward method” (LOCF; n5 1), “maximum likelihood estimation algorithm method” (MLE; n 5 1), “on available complete data method” (OACD; n 5 1), and “mixed-effects models” (MEM; n 5 2). Results of Individual Studies and Synthesis of Results Body Dissatisfaction. Among the 20 controlled studies, 12 studies included a measure of body dissatisfaction (Fig. 3). None of the 12 studies emerged as outliers, and heterogeneity was unimportant (Q 5 7.71, p 5.74, I2 5 0%). The summary effect size was d 5 0.28, 95% CI [0.15–0.41], p <.001, revealing a small but significant overall effect (g 5 .28, 95% CI [0.15–0.41], p <.001). When comparing ITT (n 5 6) versus completers (n 5 6), the moderation analysis revealed no significant TABLE 3. Methodological criterion of intention-to-treat analysis and dropout rates by condition Study (Reference) ITT Method Dropout Internet-Based Program (n) Dropout Control Condition (n) Winzelberg et al.29 NA 4 4 Celio et al.30 NA 1 3 Zabinski et al.31 NA 0 1 Zabinski et al.32 BOCF 2 0 Taylor et al.20 NA 38 21 Low et al.33 BOCF NA NA Paxton et al.35 BOCF 13 7 Heinicke et al.34 BOCF 28 34 Jacobi et al.36 NA NA NA Doyle et al.37 BOCF 7 7 Jones et al.38 BOCF 8 8 Fernandez-Aranda et al.39 NA NA NA Sanchez-Ortiz et al.40 MEM 8 13 Carrard et al.41 MLE 13 4 Carrard et al.42 NA 2 2 Fichter et al.43 OACD 7 8 Jacobi et al.44 MEM 8 3 Stice et al.45 NA 2 0 H€otzel et al.46 BOCF 54 33 Ruwaard et al.47 LOCF 13 4 Notes: ITT 5 intention to treat; NA: not applicable or not found; MEM: mixed-effects models; BOCF: baseline-observation-carried-forward method; LOCF: last-observation-carried-forward method; MLE: maximum likelihood estimation algorithm; OACD: on available complete data. MELIOLI ET AL. 24 International Journal of Eating Disorders 49:1 19–31 2016 FIGURE 3. Body dissatisfaction, drive for thinness, and internalization of the thin ideal. FIGURE 4. Shape and weight concerns. REDUCING ED SYMPTOMS USING THE INTERNET International Journal of Eating Disorders 49:1 19–31 2016 25 differences in the summary effect, p 5.89. Similarly, when comparing high-risk (n 5 2) versus nonclinical/mixed (n 5 10) participants, the moderation analysis revealed no significant differences in the summary effect size, p 5.85. Drive for Thinness. Ten studies included a measure of drive for thinness (Fig. 3). One study43 emerged as an outlier with a standardized residuals value of 22.19 (>1.96) and was removed from this analysis. Tests of homogeneity showed an unimportant heterogeneity across the nine remaining studies (Q 5 2.91, p 5.94, I2 5 0%). The summary effect size was d 5 0.47, 95% CI [0.33–0.60], p <.001, indicating a significant small effect on drive for thinness (g 5 .46, 95% CI [0.33–0.60], p <.001). When comparing ITT (n 5 3) versus completers (n 5 6), a moderation analysis revealed no significant differences in the summary effect size, p 5.60. Similarly, when comparing high-risk (n 5 2) versus nonclinical/mixed (n 5 7) participants, the moderation analysis revealed no significant differences in the summary effect size, p 5.27. Internalization of the Thin Ideal. Three studies provided effect sizes for internalization of the thin ideal, and none emerged as outliers (Fig. 3). Tests of homogeneity showed an unimportant heterogeneity (Q 5 .73, p 5.70, I2 5 0%). The summary effect size was d 5 0.36, 95% CI [0.07–0.65], p <.05, revealing a moderate positive effect on internalization of the thin ideal (g 5 .36, 95% CI [0.07–0.64], p <.05). As the three studies aimed to prevent ED using data from completers, no moderation analyses were conducted. FIGURE 5. Bulimic symptoms, negative affect, and restriction. MELIOLI ET AL. 26 International Journal of Eating Disorders 49:1 19–31 2016 Shape and Weight Concern. Nine studies provided effect sizes for shape concern, and none were outliers (Fig. 4). Substantial heterogeneity emerged for the shape concern outcome (Q 5 15.93, p <.05, I2 5 50%). The summary effect was d 5 0.35, 95% CI [0.13–0.57], p <.05, revealing a significant effect on shape concern (g 5 .34, 95% CI [0.13–0.56], p <.05). When comparing ITT (n 5 5) versus completers (n 5 4), a moderation analysis revealed no significant differences in the summary effect size, p 5.52. When comparing high (n 5 3) versus nonclinical/ mixed (n 5 6) participants, the moderation analysis revealed that the summary effect size for high-risk participants (d 5 0.74, 95% CI [0.45–1.04], p < .001; g 5 .73, 95% CI [0.44–1.02], p <.001) was significantly larger than for nonclinical/mixed participants (d 5 0.17, 95% CI [20.01 to 0.35], p 5 .066; g 5 .17, 95% CI [20.01 to .34], p 5.066), Q 5 10.68, p <.05. Nine of the studies provided effect sizes for weight concern, with no outliers. Tests of homogeneity revealed unimportant heterogeneity (Q 5 5.13, p 5.74, I2 5 0%) with a summary effect size of d 5 0.25, 95% CI [0.09–0.40], p <.05, revealing a small significant effect on weight concern (g 5 .25, 95% CI [0.09–0.40], p <.05). When comparing ITT (n 5 5) versus completers (n 5 4), the moderation analysis revealed no significant differences in the summary effect size, p 5.54. When comparing high (n 5 2) versus nonclinical/mixed (n 5 7) participants, the moderation analysis revealed no significant differences in the summary effect size, p 5.06. Five studies included combined measures of shape and weight concern, with no outliers. Moderate heterogeneity was found (Q 5 9.19, p 5.056, I2 5 47%). The summary effect size was d 5 0.42, 95% CI [0.13–0.71], p <.05, indicating a moderate significant effect on shape and weight concern (g 5 .42, 95% CI [0.13–0.70], p <.05). When comparing ITT (n 5 2) versus completers (n 5 3), a moderation analysis revealed no significant differences in the summary effect size, p 5.09. As the five studies aimed to prevent ED, no comparison was made with high-risk participants. Dietary Restriction. Thirteen studies included a measure of dietary restriction, with no outliers (Fig. 5). Tests of homogeneity revealed an unimportant heterogeneity (Q 5 7.96, p 5.79, I2 5 0%). The summary effect size for dietary restriction was d 5 0.36, 95% CI [0.23–0.49], p <.001, revealing a small overall effect (g 5 .36, 95% CI [0.23–0.49], p <.001). When comparing ITT (n 5 8) versus completers (n 5 5), a moderation analysis revealed no significant differences in the summary effect size, p 5.38. Similarly, when comparing high-risk (n 5 3) versus nonclinical/mixed (n 5 10) participants, a moderation analysis revealed no significant differences in the summary effect size, p 5.34. Bulimic Symptoms and Purging Frequency. Eighteen studies provided a measure for bulimic symptoms (Figs. 5 and 6). Two studies42,47 emerged as outliers and were removed from this analysis (standardized residuals value of 3.95 and 2.02, respectively). Tests of homogeneity revealed an unimportant heterogeneity (Q 5 9.24, p 5.87, I2 5 0%). The overall effect size was d 5 0.27, 95% CI [0.17–0.37], p <.001, revealing a small but significant effect on bulimic symptoms (g 5 .26, 95% CI [0.16–0.36], p <.001). When comparing ITT (n 5 9) versus completers (n 5 7), a moderation analysis revealed no significant differences in the summary effect size, p 5.72. Similarly, when comparing high-risk (n 5 3) versus nonclinical/mixed (n 5 13) participants, the moderation analysis revealed no significant differences in the summary effect size, p 5.11. Five studies provided a measure for purging frequency. One study47 emerged as an outlier and was removed FIGURE 6. Purging frequency. REDUCING ED SYMPTOMS USING THE INTERNET International Journal of Eating Disorders 49:1 19–31 2016 27 (standardized residuals value of 3.79). Tests of homogeneity revealed a moderate heterogeneity (Q 5 4.97, p 5.17, I2 5 40%). The summary effect size for the remaining four studies was d 5 0.30, 95% CI [0.02–0.57], p <.05, indicating an overall significant small effect on purging frequency (g 5 .29, 95% CI [0.02–0.56], p <.05). When comparing ITT (n 5 3) versus completers (n 5 1), a moderation analysis revealed no significant differences in the summary effect size, p 5.06. When comparing high-risk (n 5 2) versus nonclinical/mixed (n 5 2) participants, the moderation analysis revealed no significant difference in the summary effect sizes, p 5.13. Negative Affect. Five studies provided a measure for negative affect with no outliers (Fig. 5). Tests of homogeneity revealed an unimportant heterogeneity (Q 5 .916, p 5.92, I2 5 0%). The summary effect size for the remaining five studies was d 5 0.32, 95% CI [0.12–0.52], p <.05, indicating an overall significant small effect on negative affect (g 5 .32, 95% CI [0.12–0.52], p <.05). As the five studies aimed to prevent ED using data from completers, no moderation analyses were conducted. Between-group effect sizes were also calculated for all outcomes by excluding studies in which a wait list condition (WLC) control group was not reported (control group with minimal intervention such as a brochure were removed from this analysis). The summary effect sizes of studies exclusively including a WLC group were not significantly different from the effect sizes calculated for studies including a WLC or another type of control group (i.e., minimal intervention). Discussion The primary aim of this meta-analysis was to evaluate the efficacy of Internet-based selective prevention and intervention programs for EDs, so as to bridge the gap in meta-analytic reviews of the success of Internet-based programs targeting ED symptoms along a continuum of severity. Findings indicated that Internet-based programs were successful in decreasing ED symptomatology, suggesting that efforts to move the field toward implementing effectiveness trials are warranted. The secondary aim was to identify variables that moderated the efficacy of ED Internet-based programs. Overall, no differences in effects were found between interventions conducted in populations that included individuals with clinical diagnoses compared to those with “symptoms” only (except for shape concern) or between ITT or completers analyses, suggesting that these variables might not account for the efficacy of ED Internet-based programs. Compared with previous meta-analyses, the current study provides an up-to-date more inclusive review, including five studies32,34,35,39,42 that were not present in the previous 2014 meta-analysis,19 and by excluding programs delivered by CD-Rom. Furthermore, by excluding universal prevention studies and controlled studies between two active conditions, in contrast to the latest meta-analysis,19 our study provides summary effects of the reduction in existing ED symptoms through Internet-based programs. Finally, our study makes an important original contribution by including moderation analyses, and thus bridging a gap in the literature. Regarding the efficacy of ED Internet-based programs, consistent with previous research,17 small to moderate effect sizes were found for decreases in internalization of the thin ideal, shape and weight concern, body dissatisfaction, bulimic symptoms and purging behaviors, dietary restriction, negative affect, and drive for thinness. In addition, it is important to note that there was no evidence of negative effects. Although previous meta-analyses have reported contradictory findings regarding the efficacy of IBPPs,17–19 our results are consistent in supporting their efficacy. To date, little is known regarding moderator variables of the efficacy of Internet-based programs. Our moderator analyses revealed no significant differences between nonclinical/mixed and high-risk participants on all outcomes excepted for shape concern; a larger decrease was found among the high-risk sample. The extant literature indicated that face-to-face selected prevention produced larger decrease than universal programs for most of the outcomes, and that level of eating pathology may influence engagement and intervention effects.7 The current study suggests that Internet-based programs might be equally effective for most outcomes among nonclinical/mixed and high-risk participants. Therefore, intervention effects might depend on other variables. Regarding data analysis methodology, no difference was found in program efficacy between ITT and completer analyses. It has been argued that ITT analyses might decrease the attrition biases associated with dropout in randomized trials, and, therefore, limit bias in estimates of intervention effects.76 Internet programs have high dropout rates16 suggesting that intervention effects might differ depending on data analytic strategy (i.e., ITT and completer analyses). Nevertheless, the current meta-analysis suggests that completer analyses produce similar intervention effects as compared with ITTanalyses. MELIOLI ET AL. 28 International Journal of Eating Disorders 49:1 19–31 2016 Given the advantages of Internet-based programs, evaluating their efficacy compared with face-to-face ED programs is of particular interest. Although this was not tested in the present study, a recent metaanalysis comparing the efficacy of face-to-face and Internet CBT on psychiatric and somatic diseases concluded that both formats might be similarly effi- cacious.77 Clearly, more research in this area, including non-inferiority or equivalence studies, is warranted. Our results showed a wide range of dropout rates. As study design, implementation, guidance (e.g., self-help guided by a therapist), and intervention duration might explain dropout rates,78 further exploration of these variables as potential moderators of programs engagement is an important area for future research.17,79 Internet-based programs present numerous advantages over face-to-face ones, thus our encouraging findings highlight the importance of further implementing and disseminating these programs and extending their applications within treatment and prevention settings. For example, the Internet could offer many opportunities for aftercare interventions,80 symptom-monitoring via cell phones,81 or family-based programs.82 The Internet might also provide training opportunities for carers of individuals suffering from EDs.83–85 Moreover, as most studies have focused on interventions for bulimia or binge ED, studies evaluating Internet-based interventions for anorexia nervosa are needed.39,40,86 Our study presents a number of limitations. First, it does not provide evidence for the longterm efficacy of Internet-based programs. In addition, the lack of consensus across the literature regarding the definition of selective prevention might have led to studies being classified as one category in the present study, but another in a different meta-analysis, depending on the definition used. Furthermore, regarding methodological quality, studies reporting a low dropout rate were considered to present a low risk of bias, which could be considered as biased against studies with high ecological validity (e.g., when assessment and intervention occur entirely on-line). Nevertheless, Internet-based programs have been found to successfully decrease ED-related symptoms and risk factors. These findings highlight the importance of moving toward large-scale effectiveness trials as there is little data in this area.29,33,87 In the current study, risk status (high and low) and data analytic strategy (ITT or completer) were no moderator variables of intervention effects. Future research should thus address other moderator variables such as program interactivity, guidance frequency, and participant age. References 1. Fairburn CG, Harrison PJ. Eating disorders. The Lancet 2003;361:407–416. 2. Stice E, Hayward C, Cameron RP, Killen JD, Taylor CB. 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