and can be very distressing for both patients and their families," said Christopher Fairburn, professor and principal research fellow at the University of Oxford.

"Now for the first time, we have a single treatment which can be effective in treating the majority of cases without the need for patients to be admitted to hospital," added Fairburn, who led the study.

These disorders are a major cause of physical and psycho-social impairment in young women, affecting at least one in 20 between the ages of 18 and 30. Eating disorders are less common in young men.

Three eating disorders are recognised: anorexia nervosa, (hunger signals are ignored to control the desire to eat), accounting for 10% cases in adults; bulimia nervosa, (repeated binge eating) which accounts for a third of all cases; and the remainder are classed as atypical eating disorders, which account for over half of all cases.

In these atypical cases, the features of anorexia nervosa and bulimia nervosa are combined in a different way, according to an Oxford release.

These disorders vary in their severity, but typically involve extreme and relentless dieting, self-induced vomiting or laxative misuse, binge eating, driven exercising and in some cases marked weight loss.

Common associated features are depression, social withdrawal, perfectionism and low self-esteem. The disorders tend to run a chronic course and are notoriously difficult to treat. Relapse is common.

This new "enhanced" form of cognitive behavioural therapy (CBT-E) improves the current leading treatment for bulimia nervosa as recommended by the National Institute of Health and Clinical Excellence (NICE).

CBT-E is the first treatment to be shown to be suitable for the majority of cases of eating disorders. This new treatment derives from an earlier form of CBT. Both were developed exclusively for patients with Bulimia Nervosa by Fairburn.