My mom suffered from CFS for years, so this got my attention. My current best explanation for my mom's illness is, unfortunately, that it was in her head, given

My mom suffered from CFS for years, so this got my attention. My current best explanation for my mom's illness is, unfortunately, that it was in her head, given her many other mental and emotional problems. But could it be the other way around---that the CFS had a biophysiological origin and was a cause (or at least exacerbater) of the mental problems? Somehow I'd like to believe that as it would make her illness comprehensible and more easily treatable. But maybe this current find won't pan out as an explanation.