Background. This study seeks to identify the genetic
and environmental risk factors for the
overvalued ideas that are characteristic of bulimia nervosa, using a biometrical
approach with twin data.
Methods. The Eating Disorder Examination (EDE), which can be
used to gain continuous
measures of dietary restraint, eating concern, weight concern and shape
concern, was administered
to 325 female twins, both monozygotic (MZ) and dizygotic (DZ). For each
subscale, questions were
asked concerning the month prior to interview and lifetime prevalence (‘ever’).
Results. Model fitting indicated that there is a powerful
role of the environment in shaping women's
attitude towards weight, shape, eating and food, ranging from 38% to 100%
of the variance. For
all subscales, with the exception of weight concern, the best
explanation for individual variation was
one that incorporated additive genetic and non-shared environmental
influences. In contrast, model
fitting indicated that non-shared and shared environmental influences best
explained the variance
of weight concern.
Conclusions. With the exception of the Shape Concern
subscale, environmental factors make a
greater contribution than genetic factors to the development of
the overvalued ideas that are seen
to be one of the triggers for the development of bulimia nervosa.
Given this substantial role of the
environment influences, it seems likely that environmental manipulation
can be effective in the
prevention of bulimia nervosa.