NEW YORK (Reuters Health) - Anorexia nervosa runs a longer course in girls than in boys, research shows.

One year after undergoing treatment for anorexia, Dr. Michael Strober of the David Geffen School of Medicine at UCLA and colleagues found that girls showed a higher level of continued preoccupation with weight and eating than did boys. And while none of the boys in the current study had relapsed into full-blown anorexia at one year after treatment, 8.2 percent of girls had.

The study is the first to look at gender differences in anorexia patients, the study team points out in the International Journal of Eating Disorders. Given that the disease is much more common among females, they note, some researchers have suggested that there may be gender differences in why it develops.

To investigate, Strober and colleagues looked at 99 anorexia patients aged 13 to 17, 14 of whom were boys.

Both boys and girls had similarly severe symptoms when they entered treatment, the researchers found, and were also equally likely to suffer from anxiety disorders and traits known to be associated with anorexia such as rigidity and perfectionism. However, girls showed greater concern with weight.

One year later, the researchers found, the girls reported more concern with weight, shape and eating than the boys, and were more likely to have fallen below their recommended maintenance weight.

It's not clear, Strober and his colleagues write, whether the findings mean that girls will suffer more severe, persistent disease in the long-term than boys.

Brain differences between the sexes could be responsible for the gender differences, they note, while it's also possible that societal and cultural forces that push an ideal of thinness may be targeted more intensely to females.