The classification of medically unexplained symptoms (MUS) could have negative consequences for patients with functional somatic syndromes (FSS). By grouping related but distinct syndromes into one label, the MUS classification fails to inform clinicians about their patients' health condition. In research settings, the MUS classification makes patient samples more heterogeneous, obstructing research into the underlying pathology of FSS. Long-term studies have shown that MUS are often appraised as medically explained symptoms at follow-up and vice versa, raising doubts about the reliability of this distinction.
Keywords: chronic fatigue syndrome (CFS); fibromyalgia; functional somatic syndromes (FSS); medically unexplained symptoms (MUS); somatic syndrome disorder (SDD).