Many people with CFIDS/ME take SSRIs also known as (Selective Serotonin Reuptake Inhibitor). The reasons for this are usually to control depression; sometimes as a prescription from an unenlightened doc who thinks it's all in the patient's head.
One of the many symptoms of this strange neurosomatic disorder is the potential to be oversensitive to medication; especially SSRIs. It is reccomended that people with CFS/CFIDS/M.E. try a tricyclic antidepressant first, and no matter what, always start with very low dosages
Nobody knows exactly why this happens, but it's believed to be a result of the brain traumas that very often precede an onset of the syndrome. See Myalgic Encyphalomyalitis for a more detailed look.
My personal experiences are included below for reference:
On prozac I was extremely jittery. It looked as if the whole world was vibrating. Adrenaline coursed through my system; I would clench my fists out of fear and almost rageful mania and it was all I could do to keep myself under control. It was like some little gremlin was going through my mind and hammering every bit of it.
On Zoloft I lost a tremendous amount of weight; you could say I became anorexic (note: narzos tells me that Anorexia Nervosa is the diagnosis given to people with distorted body images, which I did not have. ) Being thin may have been a control thing during the circumstances, I'm not sure. Needless, it didn't help that I was extremely nauseated on the beast. Anxiety quadrupled, which was ironically one of the things it was trying to control. Life went on, anyway...
The topic of medications is always a touchy one for suffers of CFIDS. Some people enjoy the removal of symptoms that modern pharmaceuticals provide, however there is a large number who believe that the benifits are not worth the oft unpleasant side effects and general numbness that the more potent sedativie anti-anxiety meds can cause.
I have read that SSRIs are now being used as an immunomodulator. In either case, doses much smaller than even the lowest therapudic reccomendations are prescribed.