Cognitive behavioural therapy (CBT) is recommended as the key therapy for adults with eating disorders in the UK, according to the National Institute for Health and Care Excellence (NICE, 2017). CBT for eating disorders works by encouraging changes in behaviour to address the cognitions and emotions underpinning disordered eating and issues with body image (Mulkens & Waller, 2021).
The most recent NICE guidelines have placed even more emphasis on the use of CBT for adults with eating disorders than any which have come before (Mulkens & Waller, 2021), and it is often considered the “gold-standard” for treatment (Xie et al., 2021). This is due to research demonstrating its effectiveness in reducing both the cognitive and behavioural symptoms of eating disorders (Linardon et al., 2017). However, the evidence for the use of other therapies may be being overlooked, with some studies demonstrating Interpersonal Psychotherapy (IPT) to be a viable alternative (Miniati et al., 2018). IPT works by making associations between emotions and interpersonal interactions, and thus improves symptoms by improving personal relationships (Xie et al., 2021). Therefore, the authors of this paper argue that it might still be a suitable therapy for some people with eating disorders.
To truly understand whether IPT is comparable to CBT, the authors of this paper conducted a systematic review and meta-analysis of randomised controlled trials (RCTs) of IPT compared to CBT for eating disorders, to be able to better compare the effectiveness of interpersonal psychotherapy as a treatment.
To be included in this review and analysis, studies had to be an RCT with participants with an eating disorder, or specifically anorexia nervosa (AN), bulimia nervosa (BN), or binge eating disorder (BED). Studies needed to be comparing CBT to IPT, with multiple scales to evaluate their effects. Finally, studies needed to be written in English, be assessing IPT as a treatment for an eating disorder and not have any incomplete data or be a case report or protocol. The authors had no other exclusions around the characteristics of the samples included.
The authors selected studies based on searches of six databases, from inception up until the 30th May 2021. Titles and abstracts were reviewed by two researchers, with full text articles reviewed if they appeared to meet the inclusion criteria.
For all studies the risk of bias was reviewed using the Cochrane Risk of Bias Tool. This tool is used specifically to assess bias in randomised trials by looking at different aspects of the trial’s conduct, design, and reporting, which leads to a subsequent overall judgement on the risk of bias (Cochrane Methods, 2021).
Score on the Eating Disorder Examination (EDE) scale was analysed as the primary outcome and as a follow-up analysis, looking specifically at the difference between mean scores before and after the intervention. The Inventory of Interpersonal Problems (IIP) was measured as a secondary outcome, which can reflect the severity of an eating disorder by looking at problems with an individual’s interpersonal communication patterns.
The authors also conducted sensitivity analyses to determine the effectiveness of IPT and looked at the differences between the included studies (their heterogeneity) and the likelihood of publication bias.
Out of 468 studies identified, 10 were included in this systematic review and meta-analysis. All trials were RCTs, directly comparing IPT to CBT. These included five trials looking at binge eating disorder (BED), two trials looking at anorexia nervosa (AN), and three looking at bulimia nervosa (BN). The mean trial length was 18 weeks and mean participant ages ranged from 24.2-50.3 years. Eight trials included a follow-up period spanning more than 12 months.
Primary, secondary, and follow-up analysis results
- Similar effects of IPT compared to CBT were found for reductions in EDE scores (the primary outcome)
- Pooling the data for all studies, IPT had a mean reduction that was “close to or slightly better than CBT” (SMD=0.08, 95% CI -0.07 to 0.22, p=0.29)
- Follow-up effects were observed in all three timeframes analysed (less than 6 months, 6-12 months, more than 12 months) for both IPT and CBT, but there were no differences found between the two therapies
- An analysis of the Inventory of Personal Problems with five of the included studies showed IPT to be ‘slightly superior’ to CBT (SMD=0.32, 95% CI 0.07 to 0.56, p=0.01).
- Subgroup analysis on patients with AN and BN found:
- CBT and IPT to be equivalent in their therapeutic effects (AN: SMD=0.16, 95% CI -0.31 to 0.62; BN: SMD=0.07, 95% CI -0.10 to 0.24)
- IPT was found to have a greater effect size in younger people (SMD= 0.43, 95% CI 0.25 to 0.61, p<0.001), and people with a Body Mass Index (BMI) less than 30 (SMD=0.27, 95% CI 0.06 to 0.48, p=0.01)
- CBT was found to have a dose-response relationship (the more sessions had, the better the effect of treatment; p=0.017), which was not found for IPT.
Quality assessment and bias
Whilst all the studies used blinding, risk of bias was identified in five of the studies due to participants not being randomised (by not using random sequences entirely), and seven studies did not describe the allocation method of participants to treatment clearly. The authors found no evidence of publication bias and the heterogeneity was low.
The authors have concluded that the data from this systematic review and meta-analysis “supports IPT as a treatment strategy that can reduce eating disorder symptoms”, compared to CBT.
Strengths and limitations
Overall, the methodology of this review and analysis was strong. The authors decided to only include RCTs, which increases the reliability of the findings, as the risk of confounding factors is reduced. Two independent reviewers extracted and analysed the data and checked for risk of bias according to the PRISMA recommendations, which helps aid transparency.
However, there were various limitations:
- The conclusions offered by this review and analysis are still only tentative. This is because the authors were only able to include 10 studies, with half considered to have a high risk of bias. Additionally, the limited sample information able to be collected from each study meant that further subgroup analyses could not be conducted on things such as number of sessions, gender, drop-out rates, etc. This means it is difficult to know how these factors may be influencing the results.
- Whilst half of the studies included were specifically about BED, this diagnosis type was not included in any subgroup analyses, and no explanation was provided by the authors as to why.
Implications for practice
The findings of this review and analysis suggest IPT may be a viable alternative to CBT, and so further research needs to be conducted looking at this approach for all types of eating disorders. Whilst CBT is currently considered the ‘gold standard’, research has estimated that roughly one in four people drop out of CBT for eating disorders (Linardon, Hindle & Brennan, 2018). Therefore, the different focus of IPT (on interpersonal relationships) may mean it could be an alternative option for those dropping out of CBT. Additionally, given the results finding that IPT may be more beneficial for those who are younger, or of a lower weight, further research may also need to further look into who may benefit from IPT the most.
The authors of this paper state that there had been no previous research comparing the effects of IPT and CBT for eating disorders. However, a meta-analysis by Linardon et al., (2017) found CBT to be superior to IPT in remission rates, with CBT having larger effects on reducing cognitive symptoms and purging/binging frequencies. Findings such as this were not acknowledged by the authors of this paper and given this mixed evidence, further high-quality studies to establish the effectiveness of IPT (to influence guidelines) are yet to be seen.
Statement of interests
No conflicts of interest have been reported by the study authors.
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