IPT is based on the concept that depression is an illness which is multifactorial in nature, but is usually precipitated or perpetuated by an interpersonal situation, that is it occurs in an interpersonal context. Similar ideas can be applied to eating disorders - that their aetiology is a varied bag, but that interpersonal factors play an important role in onset and continuation of the conditions.
There is some evidence that people with eating disorders have problems with interpersonal relationships, and both clinicians and patients themselves often identify this as an area of difficulty. Naturally, this could be cause or effect, but is likely to be a combination of both. Hence, a therapy which specifically deals with interpersonal difficulties might be expected to have some impact on the course of the eating disorder.
Fairburn and colleagues have conducted two trials of therapy of an interpersonal nature for bulimia nervosa in Oxford, UK. The first (Fairburn et al 1986) compared CBT with a non-directive interpersonal approach, and found that both groups improved substantially. The second study (Fairburn et al 1993) compared CBT with behaviour therapy and IPT. Behaviour therapy had an initial good effect, but this was not maintained over follow up. CBT and IPT both had good outcome, with no tendency for deterioration. CBT worked more quickly, whereas the patients receiving IPT continued to improve following cessation of the therapy (see figure below). Six year follow up revealed that 86% of those receiving behaviour therapy fulfilled criteria for an eating disorder, compared with 37% of those who had CBT and 28% of those who received either of the focal interpersonal psychotherapies.
More recently Fairburn and colleagues have conducted a collaborative, multisite study in Stanford and Columbia Universities in the USA. This work was reported at The Fourth London International Conference on Eating Disorders (1999), and again compared IPT with CBT. 220 patients received 19 sessions of either CBT or IPT. The results mirrored those of the other trials, with both therapies having similar outcomes at long term follow-up, but CBT being more rapid in terms of symptom reduction, with most change emerging by session 4-6.
Group IPT has been used in a comparison study (Wilfley et al, 1993). This looked at the effectiveness of group CBT compared with group IPT for individuals with binge eating but without purging. Fifty six women were randomised into the two treatment groups, plus a waiting list control group. At post treatment, the CBT group had reduced bingeing by 48% (28% abstinent), the IPT group by 71% (44% abstinent) and the waiting list group by 10% (0% abstinent). There was an increase in bingeing at 6 months and 1 year compared to post treatment, but there was still an overall reduction of number of days binged by 55% for CBT and 50% for IPT at 1 year.
IPT as adapted by Fairburn for bulimia deliberately steers off discussion of current eating, once the initial sessions have been completed. This differs somewhat from IPT for depression, in that for the latter, a medical model is employed, and the individual is given the patient (or sick) role. Psychoeducation concerning the depression is considered an important part of the initial sessions, and thereafter, symptoms of depression are enquired about at the beginning of each session, reduction in symptoms are noted and fed back to the patient, and exacerbations are linked in to interpersonal events. Changes were made in the Fairburn studies so that CBT interventions were as distinguishable as possible from IPT interventions. It may be that omitting symptom enquiry and linking in to interpersonal events may dilute the effectiveness of IPT, as these factors are considered to be a very important part of IPT for depression. On the other hand, it is IPT as adapted by Fairburn which has been shown to be an effective treatment for bulimia.
Outside the constraints of a research trial, it is possible to conduct IPT using more of the patient role techniques and weekly symptom enquiry. Patients soon become able to link binge episodes with interpersonal events, and it would be interesting to see if this might further increase the efficacy of IPT for bulimia.
There is well documented evidence that IPT has a delayed onset of action in comparison with CBT. Whilst CBT has all of its effect by the end of treatment, patients with IPT tend to be slower to improve, but that improvement continues following the end of treatment. This makes theoretical sense - in IPT, patients are being encouraged to make changes in their interpersonal world and increase their interpersonal network. It would be expected that this is a process which would continue following cessation of therapy, and that it would take time to have a knock-on effect on symptoms.
Robin et al (1998) report using IPT with bulimic adolescents. They warn about extrapolating results from adult studies, but nonetheless recommend adolescent IPT as modified by Mufson et al (1993) for use in bulimic adolescents. In this case, a fifth problem area is added - single-parent family issues. They point out that the "here and now" focus would appeal to adolescents, 'whose lives revolve around their interpersonal relationships with peers, perhaps giving IPT an edge with this hard to engage population.'
In summary, IPT is gaining general recognition, and in the eating disorders world is beginning to rival CBT as an effective treatment for bulimia nervosa. IPT is also useful for binge eating disorder, and there are some tentative suggestions that it may be effective for some cases of anorexia nervosa. It is applicable across a wide age range, including adolescents and may have applications in the management of 'multi-impulsive bulimics' and bulimia with comorbid diabetes mellitus.
References
Fairburn CG, Kirk J, O'Connor M, Cooper PJ. 1986. A comparison of two psychological treatments for bulimia nervosa. Behaviour Research and Therapy 24: 629-643.
Fairburn CG, Jones R, Peveler RC, Hope RA, O'Connor M. 1993. Psychotherapy and bulimia nervosa: the longer term effects of interpersonal psychotherapy, behaviour therapy and cognitive behaviour therapy. Archives of General Psychiatry 50: 419-428.
Fairburn CG. 1993. Interpersonal psychotherapy for bulimia nervosa. In New Applications of Interpersonal Psychotherapy, Klerman GL & Weissman MM (eds). American Psychiatric Press: Washington DC.
Mufson LH, Moreau D, Weissman MM and Klerman GL. 1993. Interpersonal psychotherapy for depressed adolescents. In New Applications of Interpersonal Psychotherapy, Klerman GL & Weissman MM (eds). American Psychiatric Press: Washington DC.
Robin AL, Gilroy M, Dennis AB. 1998. Treatment of eating disorders in children and adolescents. Clinical Psychology Review 18(4): 421-426.
Wilfley DE, Agras WS, Telch CF, Rossiter EM, Schneider JA, Cole AG, Sifford L, Raeburn SD. 1993. Group cognitive-behavioural therapy and group interpersonal psychotherapy for the nonpurging bulimic individual: a controlled comparison. Journal of Consulting and Clinical Psychology 61(2): 296-305.
