Anorexia nervosa: change over time in age of onset, presentation and duration of illness.
The question as to whether anorexia nervosa as an illness has transformed itself was partially addressed in an investigation into the possible change over time in age of onset, age of presentation and the derived variable, delay between onset and presentation. These three variables were examined in 827 patients diagnosed as suffering with anorexia nervosa, who had attended the Eating Disorders Unit at the Middlesex and St George's Hospitals from 1960 to 1990. This analysis revealed a stable age of onset but a lengthening in duration of illness and associated increase of age at presentation. However, investigation of data obtained from two other tertiary referral centres revealed stability of all three variables over time. The overall conclusion was that there has been no change in the age of onset of anorexia nervosa during the past 30 years. The increasing delay in presentation to the eating disorders clinic is most likely attributable to a change in the practice of patient referrals to a national tertiary referral centre.