Although FSS are common worldwide and in all areas of medicine, diagnostic and therapeutic approaches are still controversial and not confirmed.
Several studies as to the concept and the structure of the syndrome have been performed using questionnaire or interview (9,13,14). Wessely et al. reviewed literatures and concluded that the similarities between individual syndromes outweigh the differences (4). A meta-analytic review confirmed that FSSs are related to anxiety and depression but relatively independent to them (10). Henningsen et al. reviewed management of FSS on literatures and recommended that a balance between biomedical (somatic) and interpersonal (psychological) approaches is important (5).
There have been several studies of the PSP on individual syndromes such as irritable bowel syndrome or fibromyalgia syndrome, but few studies on FSS as a whole. The bias of disease is small in our series of studies, so the findings could suggest the pathology of whole FSS independent upon diagnostic category.
The relationship between objective assessment and subjective symptoms or feelings is important in FSS. But almost studies are based on either objective or subjective index.
Both objective assessment, i.e. physiological measuring, and subjective feelings, i.e. subjective score or psychological questionnaire, were used in our studies. Relationship between them was also estimated.