This study investigated the efficacy of Emotional and Social Mind Training (ESM) a novel, group-based treatment for bulimia nervosa, compared to group-based CBT for bulimia. We hypothesised that ESM, a non-symptom-based treatment that targets the broader emotional and social deficits often experienced by sufferers of bulimic disorders, would be superior to CBT in terms of treatment outcomes. This hypothesis was not supported. Although both treatments performed well and patients in each group improved significantly, no differences in primary or secondary outcomes were found between the two treatments at the end of treatment or at follow-up. The hypotheses that social and interpersonal functioning would improve significantly more in the ESM group were also not supported. Additionally, none of these variables emerged as moderators of outcome in our analyses.
However, it is of interest that ESM performed as well as CBT, the currently recommended first line treatment modality for the treatment of BN. Abstinence and recovery rates did not differ between groups, and were comparable to those obtained in other studies of group and individual treatment for BN (e.g 
.). This gives grounds for optimism that ESM may be a viable alternative to CBT for the treatment of some individuals with BN.
Group treatment for bulimia is an underdeveloped area within the treatment research field. One key question to be answered is whether group treatment is as effective as individual treatment for BN. In the 1980s and early 1990s, numerous group therapies for bulimia were developed and trialled. A meta-analysis of group treatments for bulimia by Fettes and Peters 
reported a moderate effect size (0.75), significantly smaller than that for individual therapy. Of note, this meta-analysis included treatments from a number of different psychotherapeutic modalities.
However, Chen et al.
found no difference between individual and group CBT, although a higher proportion of individual CBT patients were abstinent from bulimic behaviours at the end of treatment, a finding which disappeared at follow-up. Similarly, Katzman et al.
found no difference in treatment efficacy between individual CBT and group CBT prefaced by four individual sessions. It may be that CBT for bulimia is particularly adaptable for groups, and that ESM, whose theoretical framework and structure is based on fairly recent developments within the broad cognitive behavioural field of research in bulimia, retains this adaptability.
Other considerations of the commonalities and differences between ESM and CBT suggest further areas for investigation. ESM, like CBT, is a structured, collaborative therapy based on a model of bulimia shared with the patient. Our clinical sense is that this structure and collaboration, particularly within a group setting, are an essential part of patients feeling safe and contained within therapy.
However, unlike CBT, ESM is less symptom- and more emotion and interpersonally-focused. It targets the broader pathology associated with and hypothesised to underlie BN, including poor social functioning, low self-esteem and poor emotional regulation. It focuses more on group processes, particularly interactions between group members. It also uses some experiential techniques, for example therapeutic writing.
As discussed above, much of the motivation for developing ESM to focus on these underlying issues is because of the substantial and accruing evidence that a large subset of sufferers of bulimia are particularly impaired in these areas 
. We hypothesised that this group may benefit preferentially from ESM over CBT. Disappointingly our moderator analysis did not show a differential treatment effect depending on level of socio-emotional impairment at baseline, however the study was probably not adequately powered for this. Moreover, we were unable to collect data on these socio-emotional outcomes at end of treatment and follow-up and future studies of ESM should assess these.
This study had a number of limitations. Our rate of drop-out was high, and this limits the strength of the conclusions we are able to draw. The phenomenon of high drop out is common in bulimia treatment research with rates higher than in other fields 
. It may also be affected by our inner-city London participant population. Agras et al. 
compared two treatments for bulimia in Stanford and New York City, and found significantly lower retention rates in NYC. However, the level of drop-out did mean that the study lacked the intended power to enable us to confirm our hypotheses. It will be important in future studies to address this issue to attempt to minimise the level of drop-out.
One particular strength of the study was its ecological validity. It was based in a busy Outpatient clinic in a deprived inner-city area in South London, with all the attendant practical issues associated with such a setting, including stretched clinicians and administrators, and limited practical resources. Also, patients did not receive a monetary compensation and their access to treatment was not dependent on participation in this study. It is encouraging that positive results may be obtained in such a realistic environment.