Chronic fatigue syndrome (CFS) is characterised by severe and disabling fatigue lasting at least 6 months. It affects mental and physical functioning and can be accompanied by musculoskeletal pain, sleep disturbance, impaired concentration and headaches. Some people with CFS have concomitant depression and anxiety.
So to answer your questions most people do eventually recover and yes it does affect peoples mentally. I can't help with how it affects relationships though sorry.

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