The Fukuda et al. (1994) criteria for chronic fatigue syndrome (CFS) specifies that a symptom can only be included within a diagnosis if it is experienced concurrently or following the onset of fatigue.
In order to investigate this issue, participants provided information on persisting symptoms (lasting greater than six months) and whether those symptoms occurred prior to, concurrently, or following the onset of their fatigue.
More symptoms were experienced after the fatigue onset than prior to the fatigue onset; however, a considerable number of participants reported experiencing persisting symptoms prior to the onset of CFS. Particularly, rates of hay fever and asthma were higher prior to the illness.
Investigating symptoms prior to the onset of the illness might provide investigators with ways to better understand the etiology of this illness.
An investigation of symptoms predating CFS onset, by M Evans, M Barry, Y Im, A Brown, LA Jason in J Prev Interv Community 2015; 43(1):54-61