Overall, physiological indices relevant to ANS were hypo-reactive to mental work stress and psychological tension indices were high in the FSS patients compared with healthy controls. These findings suggest that FSS patients have hypo-functional stress responses, and could not cope with the stress properly, so felt higher subjective tension feelings.
While these findings were results by averaging, the cluster analysis divided the FSS patients into two clusters by autonomic response to the stress: high-lability and low-lability group (the number of low-lability group was larger). The mood scores were higher in the high-lability group than in the low-lability group.
Moreover, heart rate variability, well known as an index of autonomic function, was reduced at the pre-stress resting period in FSS patients. This finding suggests that both reduced autonomic lability in pre-stress period and attenuated autonomic response to stress exist, and both dysfunctions would interactively yield the maladaptive process.
These tendencies were not depend upon diagnosis, suggesting the existence of common pathophysiology in FSS patients.