August 3 (HealthDay News) -- Anorexia nervosa is more common than previously thought, according to a study of more than 3,000 Finnish women born between 1975 and 1979.

The study, by Finnish and American researchers, also found that, in many cases, anorexia symptoms come and go.

The researchers found that about 2.2 percent of young women suffered from severe anorexia nervosa, while up to 5 percent of the women suffered at least some degree of anorexic symptoms (self starvation and obsessive anxiety about weight) sometime during their lifetime.

Symptoms of anorexia nervosa usually appeared between ages 10 and 25, while the peak of illness onset was between ages 15 and 19.

The researchers from the University of Helsinki and Columbia University, New York City, found that recovery from anorexia was usually slow and gradual. Initially, women regained lost weight and resumed menstruation. But it took five to 10 years for them to readjust their attitudes about body shape and weight.

By age 30, up to 70 percent of women with anorexia had recovered from the illness. The average duration of the disorder was three years: About 25 percent of patients recovered within a year, about 33 percent within two years, and about 67 percent within five years after the onset of anorexia symptoms.

The study was published in the American Journal of Psychiatry.

SOURCE: Columbia University, news release, Aug. 1, 2007