Studies of psychological treatment

Cognitive-behavioural therapy

The most intensively studied psychological treatment is a specific form of cognitive-behavioural therapy. This was the first promising treatment described (59> and it remains the leading treatment for the disorder. The treatment and its rationale are described in Chapte£i6:3.2.2

Cognitive-behavioural therapy is conducted on an outpatient basis and involves 15 to 20 sessions over about 5 months. It is suitable for all patients bar the small minority (less than 5 per cent) who require hospital admission.

The findings of the studies of cognitive-behavioural therapy (over 20 controlled trials) are summarized below (adapted from Wilson and Fairburn (57)).

1. The drop-out rate with cognitive-behavioural therapy (about 15 per cent) is about half that seen with antidepressant drugs. The treatment is also more acceptable to these patients than treatment with medication.

2. Cognitive-behavioural therapy has a substantial effect on the frequency of binge eating and purging. On average, among treatment completers there is about an 80 per cent reduction in the frequency of binge eating, and a cessation rate of about 60 per cent.

3. The effects of cognitive-behavioural therapy appear to be well maintained. Most of the recent studies have included a 6 to 12 month follow-up period. The relapse rates are low.

4. Cognitive-behavioural therapy affects most aspects of the psychopathology of bulimia nervosa including the binge eating, purging, dietary restraint, and the overevaluation of shape and weight. In common with other treatments, the level of depression decreases as the frequency of binge eating declines. Social functioning and self-esteem also improve.

5. Cognitive-behavioural therapy is more effective than delayed treatment (that is, a waiting list control group), other psychological treatments (other than possibly interpersonal psychotherapy; see below), and antidepressant drugs at reducing the frequency of binge eating and purging. Among the other psychological treatments studied have been supportive psychotherapy, focal psychotherapy, supportive-expressive psychotherapy, interpersonal psychotherapy, hypnobehavioural treatment, stress management, nutritional counselling, behavioural versions of cognitive-behavioural therapy, and exposure with response

prevention.

No consistent predictors of response to cognitive-behavioural therapy have been identified. Severity of symptoms at presentation, a history of anorexia nervosa, low self-esteem, and the presence of borderline personality disorder have been associated with worse outcome in some studies but not others. Initial response (over the first 4 weeks of treatment) is emerging as a useful predictor of subsequent outcome.

The mechanism(s) of action of cognitive-behavioural therapy have yet to be established. It seems that the cognitive procedures are required for progress to be maintained since behavioural versions of the treatment are associated with a greater risk of relapse (as illustrated in Fig 5).

Fig. 5 Rates of abstinence from both binge eating and purging among patients with bulimia nervosa allocated to cognitive-behavioural therapy (CBT), behaviour therapy (BT), and interpersonal psychotherapy (IPT). (Reproduced with permission from C.G. Fairburn et al. (1993). Psychotherapy and bulimia nervosa: the longer-term effects of interpersonal psychotherapy, behaviour therapy and cognitive behaviour therapy. Archives of General Psychiatry, 50, 419-28.)

8. There is evidence that the combination of cognitive-behavioural therapy and antidepressant drugs may be more effective than cognitive-behavioural therapy alone in reducing anxiety and depressive symptoms.

9. Simpler forms of cognitive-behavioural therapy show promise. These include brief versions of the treatment designed for use in primary care and cognitive-behavioural self-help in which patients follow a cognitive-behavioural self-help programme either on their own (pure self-help) or with the guidance of a therapist (guided self-help).(6 ■61>

Interpersonal psychotherapy

Interpersonal psychotherapy is the leading alternative to cognitive-behavioural therapy. This treatment was originally devised by Klerman et al. (62> as a treatment for depression (see ChapteL§.;..3,3). It is a focal psychotherapy, the main emphasis of which is to help patients identify and modify current interpersonal problems. The treatment is both non-directive and non-interpretative and, as adapted for bulimia nervosa, (63> it pays little attention to the patient's eating disorder. It is therefore very different to cognitive-behavioural therapy. In a comparison of cognitive-behavioural therapy, interpersonal psychotherapy and a behavioural version of cognitive-behavioural therapy, interpersonal psychotherapy was found to be the least effective of the three treatments at the end of treatment but the proportion of responders continued to increase such that it was as effective as cognitive-behavioural therapy by 8 and 12 month follow-up (64) (see Fig 5), and indeed, 5years later.(53» The marked difference between the two treatments in their procedures and temporal influence suggested that, although they were equivalent in their eventual effects, each treatment operated through specific mechanisms. A recent large-scale replication of the cognitive-behavioural therapy versus interpersonal psychotherapy comparison has confirmed these findings.

Exposure with response prevention

This is an adaptation of the behavioural treatment for obsessive- compulsive disorder (see C.ha.p.teLl.S) in which patients with bulimia nervosa are presented with cues that generally precede binge eating or vomiting and are then prevented from engaging in their usual response. It was advocated in the 1980s both as a treatment in its own right and as an element of cognitive-behavioural therapy. It is difficult to administer for a number of reasons: patients find it aversive; it is procedurally complex; and the sessions are time-consuming. The studies of its use suggest that it conveys no benefit over standard cognitive-behavioural therapy. (5 ^

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