creased risk of bipolar and depressive diso rders has also been found among first-degree
relatives of individuals with anorexia nervos a, particularly relati ves of individuals with
the binge-eating/purging type. Concordance rates for anorexia nervosa in monozygotic
twins are significantly higher than those for dizygotic twins. A range of brain abnormali-
ties has been described in an orexia nervosa using functional imaging technologies (func-
tional magnetic resonance imaging, positro n emission tomography).  The degree to which
these findings reflect changes associated with  malnutrition versus primary abnormalities
associated with the disorder is unclear.
Culture-Related Diagnostic Issues
Anorexia nervosa occurs across culturally and so cially diverse populations, although available
evidence suggests cross-cultural variation in its occurrence and pres entation. Anorexia ner-
vosa is probably most prevalent in post-industr ialized, high-income coun tries such as in the
United States, many European c ountries, Australia, New Zealand,  and Japan, but its incidence
in most low- and middle-income countries is uncertain. Whereas the prevalence of anorexia
nervosa appears comparatively low among Latino s, African Americans, and Asians in the
United States, clinicians should be aware that mental health service utilization among individ-
uals with an eating disorder is significantly lo wer in these ethnic groups and that the low rates
may reflect an ascertainment bias. The presenta tion of weight concer ns among individuals
with eating and feeding disorders varies substa ntially across cultural contexts. The absence of
an expressed intense fear of we ight gain, sometimes referred to  as “fat phobia,” appears to be
relatively more common in popu lations in Asia, where the rati onale for dietary restriction is