True about chronic fatigue syndrome are all except ?

Chronic fatigue syndrome (CFS) is a disorder characterized by persistent and unexplained fatigue resulting in severe impairment in daily functioning. Besides intense fatigue, most patients with CFS repo concomitant symptoms such as pain, cognitive dysfunction, and unrefreshing sleep. Additional symptoms can include headache, sore throat, tender lymph nodes, muscle aches, joint aches, post-exeional malaise, feverishness, difficulty sleeping, psychiatric problems, allergies, and abdominal cramps . Ref - Harrisons 20e p3254