(NEW YORK) -- Taylor wants to like herself, but she can't turn off the voice inside her head that tells her she's not good enough and that the way she looks isn't perfect.
"It really feels like it is a second person inside of you," she said. "It's like your best friend but your enemy at the same time. It's hard to distinguish sometimes the ED talking and what's Taylor talking."
"ED" is the nickname Taylor, 20, gives to her eating disorder diagnosis, which, as she puts it, was "switched all over the place."
"Originally I was diagnosed with bulimia," she said. "Then my symptoms didn't match bulimia. So then they diagnosed me as anorexia, binge/purge type, because there are two different types. And then I didn't meet the weight criteria for anorexia. So then they said, 'OK, you have EDNOS.' And I was like, 'Well, what is that?'"
EDNOS stands for "eating disorder not otherwise specified," and up to 70 percent of all eating disorders come under the EDNOS banner. According to the National Association of Anorexia Nervosa and Associated Disorders, 24 million people in the U.S. of all ages and genders suffer from an eating disorder.
Many of the EDNOS symptoms are the same as other eating disorders, such as bulimia or anorexia, but don't fully meet the criteria of those disorders. On the other hand, EDNOS sufferers might exhibit a combination of eating disorders, such as being severely strict with counting calories but then still purging after eating.
The issues lie as much in the mind as in the meal, said Dr. Douglas Bunnell, a clinical psychologist and vice president of The Renfrew Center, a renowned eating disorder treatment program with 11 locations in nine states.
"It's still a misperception out there that these are relatively benign sorts of disorders or diets gone bad," Bunnell said. "These are life-threatening, serious illnesses. They have the highest mortality rate of any psychiatric diagnosis."
After receiving an EDNOS diagnosis, Taylor said she felt a little disappointed, as if her condition wasn't as serious as the more well-known eating disorders.
"Because you only hear about bulimia and anorexia," she said. "A lot of people don't think -- just because you don't meet the weight criteria, 'Oh, you don't have an eating disorder.'"
But EDNOS is a deadly condition, with a morality rate of 5.2 percent -- higher than both anorexia and bulimia -- despite the fact its sufferers often look healthy.
Watch Nightline's full report on EDNOS and those who suffer from it Wednesday at 11:35 p.m. ET.
Copyright 2012 ABC News Radio