Anticipation of and response to exercise in adolescents with CFS: An experimental study, 2021, Loades, Chalder et al

The strange thing is that ME/CFS patients actually did perform worse than the two control groups on the test. The difference is quite large.

So, if ME/CFS patients thought they would perform worse, then they were simply correct? It makes all the speculation in the paper about unhelpful beliefs a bit strange. There's one sentence in the paper that acknowledges this. It reads :

"But of course, it is also possible that the participants are reasonably good at predicting their performance."
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The authors also suggest that the expectations of parents may also contribute to disability. They write: "Parental expectations may influence their child’s activity levels, for example, by understandably advocating rest and thus inadvertently contributing to reduced physical fitness."

But if one looks at the scores on the question: How well do you think your child is going to do on this task? 50% represents average performance” (0 Not at all well-100 Extremely well). The ME/CFS parents had a mean around 50 while the controls groups a mean around 90. So again it seems that the ME/CFS groups had a realistic expectation, in contrast to the control group.