In any varying system, which could be athletic performance or the waxing and waning symptoms of a chronic illness, any extreme variance is statistically likely to be followed by a more typical variance. This means that when you have bad symptoms, it’s likely that your symptoms will eventually become milder, or regress to the mean. This also means that any treatment you take when your symptoms are severe is likely to be followed by a lessening of those symptoms, creating the illusion that the treatment worked.
