DBT-BED, a recently developed treatment based on the affect-regulation model of binge eating, has heretofore been tested in only one randomized trial (Telch et al., 2001
), which showed that DBT-BED was better than no treatment in reducing binge eating. Because there was no comparison with an active control, it is possible that the effects of therapy were due to nonspecific therapeutic elements. Therefore, the current study compared DBT-BED to a structurally equivalent nonspecific psychotherapy treatment to examine whether the hypothesized active ingredients of DBT-BED would show a level of effectiveness beyond that due to shared common therapeutic effects (e.g., therapeutic optimism).
Participants in both the DBT-BED and active comparison group therapy (ACGT) improved substantially in achieving this study’s primary outcomes, abstinence and reducing binge frequency. Posttreatment abstinence rates were 64% for DBT-BED and 36% for ACGT, and 12-month follow-up abstinence rates were 64% and 56% for DBT-BED and ACGT, respectively. Although the DBT-BED group achieved abstinence and reductions in binge frequency more quickly (e.g., at posttreatment), there were no significant differences between the groups at any time during the follow-up period.
The posttreatment abstinence rate in the ACGT group was similar to abstinence rates found in the control arms of other BED treatment outcomes studies. For example, ACGT’s posttreatment abstinence rate is comparable to the mean placebo response rate of 33% reported in a review of psychopharmacological trials for BED by Carter and colleagues (2003)
and a 42% abstinence rate (at 24 weeks posttreatment) in the placebo arm of a recent pharmacotherapy randomized controlled study for BED (Wilfley et al., 2008
). In addition, such rates are similar to the mean placebo rates (from meta-analyses) of other psychiatric illnesses including major depression (Walsh, Seidman, Sysko, & Gould, 2002
) and bipolar mania (Sysko & Walsh, 2007
The improvement (i.e., increase in abstinence rates) from posttreatment (36%) through the 12-month follow-up assessment (56%) is striking. One interpretation for this improvement is that it is attributable to the delayed treatment effects of ACGT. In this sense, ACGT may be similar to IPT for bulimia nervosa, which initially results in significantly lower postabstinence rates than CBT but which is statistically indistinguishable at 1 year after treatment (Agras, Walsh, Fairburn, Wilson, & Kraemer, 2000
). Another possibility is that the improvement is due to the high rate of spontaneous remission seen over time in BED, which could result in the lessening of observed posttreatment differences. As studies on the temporal course of binge eating disorder (e.g., Fairburn, Cooper, Doll, Norman, & O’Connor, 2000
; Fichter & Quadflieg, 2007
) reveal, binge eating patterns can be unstable over time. Without a wait-list control, it is difficult to distinguish between these competing hypotheses. Indeed, even with such a control it is difficult, as the anticipation of future treatment (often offered to patients after the wait-list period) may diminish this rate of spontaneous improvement, particularly in the BED population.
In terms of the secondary measures, the greatest impact was demonstrated via three medium effect sizes, each of which favored DBT-BED over ACGT: the Eating Disorder Examination (EDE)-Restraint subscale at both posttreatment and 12-month follow-up, and the EDE-Eating Concerns subscale at posttreatment.
Small effect sizes favoring DBT-BED over ACGT were found at posttreatment for the three subscales of the EES and the BDI. However, at the 12-month follow-up, none of the emotion regulation-measures demonstrated meaningful changes favoring DBT-BED over ACGT. At the 12-month follow-up, small effect sizes favoring improvement in ACGT over DBT-BED were found for the DERS and the negative subscale of the PANAS.
A significant finding from this study was the very low dropout rate in the DBT-BED group compared the ACGT group. These results, in combination with the 18% dropout rate found by Telch and colleagues (2001)
, suggest that DBT for BED is an acceptable treatment for many participants, though further comparisons against other than a wait-list or nonspecific control are needed.
This study confirms and extends the earlier investigation of DBT-BED (Telch et al., 2001
) by employing the same manualized DBT-BED treatment but in addition, compares DBT-BED to an active control and lengthens the follow-up period to 12 months. Telch et al. (2001)
found posttreatment ITT abstinence rates of 73% for DBT-BED and 9% for those in the wait-list condition. At the 6-month follow-up assessment, the ITT abstinence rate for those in DBT-BED was 54.5% (Telch et al.). The current study’s posttreatment abstinent rate of 64% for DBT-BED participants was somewhat lower than that found by Telch and colleagues. This disparity may be accounted, at least in part, by sample differences between the two studies. The inclusion criteria were broadened in the current study to increase the generalizability of the findings. Specifically, individuals on stable doses of psychotropic medications and both men and women were included, whereas the earlier study excluded those on psychotropics and entered women participants only. The inclusion of participants on psychotropics may have resulted in a slightly higher level of depressive symptomatology reported by group members, as reflected in the higher pretreatment BDI mean of 17.9 ± 9.4 in this study compared to 12.8 ± 7.4 in the earlier study. Previous research (Grilo, Masheb, & Wilson, 2001
; Stice et al., 2001
) clustering BED patients according to affective and restraint measures has shown poorer response to treatment in those with more severe affective (e.g., BDI) scores.
The present study’s lack of evidence for greater improvements on emotion-regulation measures among the DBT-BED versus ACGT groups replicates Telch and colleague’s (2001)
lack of significant posttreatment differences on such measures between DBT-BED and a wait-list control. In other words, neither study’s findings resulted in a measurable impact of DBT on emotion regulation. The lack of differentiation between DBT-BED and ACGT is puzzling and may indicate a true absence of a major DBT-BED treatment impact on emotion regulation or it may reflect the lack of consensus within the field on how to conceptualize and measure emotion regulation (Gratz & Roemer, 2004
). Of note, the largest effect size favoring DBT-BED over ACGT was in reducing EDE-Restraint subscale scores at posttreatment and at the 12-month follow-up. It is not obvious why DBT-BED would impact EDE-Restraint as DBT-BED, unlike CBT, does not specifically discuss patterns of food intake or rules regarding food. It is possible that through DBT-BED’s emphasis on nonjudgmental acceptance of emotions, emotionally charged rules regarding food may decrease. In other words, DBT’s emphasis on mindfulness may act indirectly to help reduce the restrictive mindset often found in chronic dieters who, after breaking cognitive barriers, tend to eat more (Heatherton & Polivy, 1992
; Polivy & Herman, l995
The study has a number of limitations. Despite the best efforts to design a highly credible and acceptable comparison treatment and to retain participants for study assessments (even if they dropped from treatment), dropout rates from treatment as well as study assessments were higher in the ACGT than DBT-BED group. For example, the drop-out rate for ACGT was 33.3% (17/51). About one third (35%, 6/17) of these 17 dropouts took place within the first month of treatment, whereas the remainder (65%, 11/17) of dropouts were evenly distributed over Weeks 5–18. This suggests that patients dropped both due a lack of credibility of ACGT once it was under way (despite the lack of significant differences in postrandomization ratings of suitability) as well as a sense that, while credible, they did not find the treatment helpful over time.
Despite this differential dropout rate, nearly all patients (97%; 98/101) were willing to complete at least posttreatment assessments on the primary outcome measures of binge days and abstinence. However, this number of study assessment completers decreased over the follow-up period, particularly among those assigned to ACGT. By the 12-month follow-up, 98% (49/50) of the DBT-BED participants completed assessments on at least the primary outcome measures versus only 76.5% (39/51) of the ACGT participants. The maximum likelihood estimation approach employed in this study assumes that dropout may be associated with observed variables such as treatment assignment (i.e., DBT-BED or ACGT) and baseline measures. However, this approach does not take into account group differences that might be associated with unobserved variables (Little & Rubin, 2002
). In other words, if dropout rates from assessment are not missing completely at random, statistical estimates of differential outcomes between the groups would be impacted (e.g., Graham, 2009
). A related limitation is that treatment credibility was not assessed prerandomization. Grilo and Masheb (2005)
, in asking participants to rate the extent to which the study’s two treatment options are logical, provides a useful example of such a rating. This current study was under way, however, after the publication of that study. Suitability was measured at postrandomization, however, as well as after Session 1 and at the end of treatment. It was not measured at the 12-month follow-up. Without the combination of baseline as well as postrandomization ratings (taken at various points during the course of treatment and follow-up), the effect of the postrandomization suitability as a potential mediator of treatment outcome or dropout status cannot be determined.
It is important to acknowledge that an adapted version of DBT (DBT-BED) and not standard DBT was implemented. DBT-BED, originally developed by Telch (1997b)
for the earlier Telch et al. (2001)
study, is based on the principles of standard DBT. However, to make DBT-BED more comparable in terms of format, length, and cost to other existing BED treatments (e.g., CBT and IPT showed efficacy for BED participants using twenty 2-hour group therapy sessions; Wilfley et al., 1993
; Wilfley et al., 2002
), the format of standard DBT treatment was modified. DBT-BED modifications included using group therapy only (versus individual plus group therapy) and shortening treatment duration to 6 months (versus 12 months), and consequently omitting one of standard DBT’s four modules (Interpersonal Effectiveness). By using the same DBT-BED manual utilized by Telch et al. (2001)
for the current study, replication and extension of the former was possible. However, the effect of using an adapted version versus standard DBT cannot be determined from this study. Furthermore, whereas adherence to the adapted version of DBT-BED was assessed, treatment adherence scores to standard DBT, which has a formalized coding standard via the Linehan Behavioral Tech group, were not obtained.
Despite these limitations, this study has a number of important strengths. It is the first to compare the posttreatment and longer-term outcome of DBT-BED to an active, carefully designed comparison therapy to attempt to control for the effect of common therapeutic factors. In doing so, it provides the first confirmation and extension of the earlier Telch et al. (2001)
study comparing DBT-BED to a wait-list control. Other strengths include a moderately large sample size, high retention rate for assessments, and follow-up assessments up to 12 months following treatment cessation. This longer follow-up period is especially valuable given mixed findings regarding the fluctuation of binge eating behaviors within BED over time (Fairburn et al., 2000
; Fichter & Quadflieg, 2007
; Pope et al., 2006
In conclusion, the data suggest both DBT-BED and ACGT were beneficial in reducing binge eating. Compared to ACGT, DBT-BED appeared more acceptable to patients as indicated by a much lower dropout rate and a higher follow-up assessment completion rate. The overall lack of differential impact with the emotion-regulation measures (as measured by effect sizes) suggests that DBT-BED’s effects were attributable to therapeutic elements shared across both treatments (see also Safer & Hugo, 2006
). DBT-BED yielded faster rates of improvement in the primary outcome measures, with higher binge abstinence and lower rates of binge eating at the end of treatment, but this differential effect was lost over follow-up.