OBJECTIVE: Since patients being treated for bulimia nervosa constitute
only a minority of persons with the disorder, the cases seen in clinics may
be subject to sampling bias. The aim of this study was to investigate
sampling bias as it affects secondary referrals for bulimia nervosa.
METHOD: The personal and family characteristics of a consecutive series of
60 women with secondary referrals for bulimia nervosa (clinic subjects)
were compare with those of 83 subjects with bulimia who were recruited
directly from the community. Most of the data were collected by interview.
RESULTS: The demographic characteristics of the two groups were similar.
The clinic subjects had a more severe eating disorder and much greater
impairment of social functioning. There was no difference between the
groups in duration of the eating disorder or level of general psychiatric
disturbance. The community subjects were heavier and had stronger family
histories of obesity. CONCLUSIONS: There is sampling bias among secondary
referrals for bulimia nervosa. The relative absence of persons prone to
obesity among secondary subjects is important, since there is evidence that
vulnerability to obesity is a poor prognostic feature as well as being a
risk factor for the development of bulimia nervosa. The greater social
impairment among the clinic subjects is suggestive of greater personality
disturbance in this group. Caution is warranted when generalizing from
clinic cases to the disorder as a whole.