The cognitivebehavioural account of anorexia nervosa and bulimia nervosa

Cognitive distortions are a prominent feature of anorexia nervosa and bulimia nervosa, and they have long been regarded as their 'core psychopathology'. For example, in the 1970s the psychotherapist Bruch(1> emphasized the 'relentless pursuit of thinness' of patients with anorexia nervosa, and Russell,(2) in the original paper on bulimia nervosa, highlighted these patients' 'morbid fear of becoming fat'. In both disorders thinness and weight loss are idealized and sought after, whereas there are strenuous attempts to avoid weight gain and any perceived 'fatness'. At the heart of this psychopathology is the tendency to judge self-worth largely, or even exclusively, in terms of shape and weight. Whereas it is usual to evaluate self-worth on the basis of perceived performance in a variety of domains (such as interpersonal relationships, work, sport, artistic ability, and so on), people with anorexia nervosa and bulimia nervosa evaluate themselves primarily in terms of their shape and weight.

To a varying degree, there may be other more general cognitive distortions. The most common is low self-esteem. Many of these patients have deep-seated and long-standing doubts about their self-worth. These encourage self-evaluation in terms of their shape and weight, since dieting and weight loss are socially reinforced in women, and since appearance, and more especially weight, seem more controllable than many other aspects of life. (3) Perfectionism is the other characteristic cognitive distortion and, like low self-esteem, it tends to antedate the eating disorder. (.i5> Perfectionism is especially prominent in anorexia nervosa. (5>

According to the cognitive view of anorexia nervosa and bulimia nervosa, these patients' extreme concerns about shape and weight are of central importance in maintaining the two disorders (Fig 1). Most of the other clinical features can be understood as being secondary to them. Ihe dieting and resultant weight loss are obvious secondary features, as are the preoccupation with thoughts about food, eating, shape, and weight, the self-induced vomiting, and the overexercising and laxative misuse.

Fig. 1 Ihe cognitive view of the maintenance of bulimia nervosa. (Reproduced with permission from C.G. Fairburn (1997). Eating disorders. In Science and practice of cognitive behaviour therapy (ed. D.M. Clark and C.G. Fairburn). Oxford University Press.

Binge eating is the only feature that is not obviously a direct expression of the concerns about shape and weight. It is present in all patients with bulimia nervosa (by definition) and a subgroup of those with anorexia nervosa. It is likely to be the result of these patients' particular type of dieting and their perfectionist standards. Patients with anorexia nervosa and bulimia nervosa severely restrict their food intake and are therefore under continuous physiological pressure to eat, but it is the form of their dieting that makes them particularly prone to binge. Rather than having general guidelines about how they should eat, these patients impose upon themselves multiple extreme, and highly specific, dietary rules. These rules concern when they should eat (or rather when they must not eat, for example not before 6 p.m.), exactly what they should eat (or rather, what they must not eat, so that most patients have a large list of 'forbidden foods'), and the overall amount of food that they should eat (e.g. less than 1000 kcal daily). Most patients attempt to follow many such dietary rules, but this proves almost impossible.

Accompanying the dietary rules is the tendency to react extremely negatively to the breaking of them. Even minor dietary slips are viewed as evidence of lack of self-control (an example of dichotomous or 'black and white' thinking) and, characteristically, this leads to the temporary abandonment of control over eating. The result is a pattern of eating in which extreme dieting is punctuated by repeated episodes of overeating (binge eating). The binges are particularly likely to occur at times of negative mood with all types of negative mood seeming to undermine these patients' ability to control their eating. Conversely, binge eating tends to moderate negative mood as a result of the sense of release that accompanies starting to binge, the positive connotations associated with eating certain foods, the drowsiness that follows eating large quantities of carbohydrate, and in those who vomit, the tension-relieving effect of self-induced vomiting. These positive effects are short-lived, however, and are gradually supplanted by mounting regret and self-disgust, and heightened fears of weight gain and fatness. As a result, patients become even more determined to restrict their food intake, thereby establishing a vicious circle.

A second vicious circle links the binge eating and compensatory 'purging' (the term used for self-induced vomiting or the misuse of laxatives or diuretics). Since these patients (mistakenly) view these forms of behaviour as effective means of compensating for binge eating (see C.h.a.pt§L..4;10.2), once they have been adopted a barrier against overeating is removed. In the case of self-induced vomiting, binge eating is further encouraged by the fact that it is easier to vomit if the stomach is full. As illustrated in Fig 1, once this vicious circle is established, the repeated purging further worsens self-esteem.

In anorexia nervosa, certain of the psychological and physiological effects of starvation (see C.h.a.pt§1..4.:10.:1) also serve to maintain the eating disorder'6). For example, reduced gastric motility results in a sense of fullness even after eating modest amounts of food, eating in a ritualistic manner has the effect of slowing down the act of eating, preoccupation with thoughts about food and eating exaggerates concerns about eating, lowering of mood intensifies negative self-evaluation, and social withdrawal magnifies self-absorption.

There is a third maintaining process in anorexia nervosa—the fact that most of these patients do not view themselves as having a problem. Whereas the great majority of patients with bulimia nervosa find their binge eating aversive, and are therefore keen to receive help, there is little about the anorectic state that is 'egodystonic'. This is because these patients' behaviour (dieting and other weight loss behaviour) and its effects (weight loss and increasing thinness) are entirely consonant with their goals (the pursuit of weight loss and thinness, and the avoidance of weight gain and fatness) with the result that they see little need to change. When they do present for treatment, they do so reluctantly or at best hesitantly.

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