Sudden onset vs. gradual onset in long-term ME/CFS

55.6% of the long-term group reported "sudden" onset of ME/CFS, which we defined as occurring over a few hours to a few weeks.

Those reporting a gradual onset had a significantly higher allergy severity score (t = 2.07; df = 248; p< .04).

We found no significant differences between sudden vs. gradual onset on any of the other illness severity measures, nor any difference in age at onset between the two groups.