Several doctors did agree that a psychiatric disorder is often seen as a secondary symptom of CFS and other chronic diseases. Komaroff said it's natural for people to develop anxiety and depression after getting sick with a chronic disease, and it shouldn't be confused with a risk factor.
"Having an illness suddenly develop out of the blue, where doctors aren't sure what it is and there aren't standard tests for it will have a psychological effect on the person," said Komaroff. "It would on me."
Dr. Ellen Slawsby, director of pain services at Benson Henry Institute for Mind Body Medicine at Massachusetts General Hospital, said that she does not see as high of a prevalence of personality disorder in her clinic as was found in the study population.
"The depression that I have observed seems to be secondary to the illness setting," said Slawsby. "Many folks are told their fatigue and pain is all in their head, but I always go with the basis that there is something there."
Unger points out that this could be the case in the study's CFS patients.
"It's not clear whether any personality features identified in people with CFS in this study are a result of having CFS or if instead they are a risk factor for developing CFS," said Unger.
And for Sparrow, who was in her 20s with "the world at her feet" when she suddenly became ill, depression came soon after the diagnosis.
"I'm on depressive medication because the illness made me so depressed," said Sparrow. "I don't understand when people say that this is all in my head. Why, when I was 24 years old with the best job I could ask for, would I give it up to be at home alone in my bed?"
Penny Cowan, executive director and founder of the American Chronic Pain Association, said that it's tough road for chronic fatigue patients because there is no magic pill that will treat the disease and make it all go away.
"CFS has gotten its share of bashing because people don't always believe it," said Cowen, who has suffered from chronic pain for more than 30 years and started the association as a resource for people who share her illness. "There is no 'aha' moment for treating the disease."
"But this is something we have to learn to live with," she continued. "And they aren't able to tell us how to do that."