The Relation of Physical Comorbidity and Multimorbidity to Fibromyalgia, Widespread Pain, and Fibromyalgia-related Variables.

FM and FMV are associated with an increase in the number of comorbidities, and the association can be measured quantitatively. However, the association of WSP and FM may be an effect of definitions of WSP and FM, because comorbidity increases are also present with subsyndromal levels of both conditions.