This is a really shockingly poor paper I am surprised that peer reviewers didn't just cry when presented with this. I really cannot understand how they could possibly get to publish this work.
Children with CFS had higher levels of psychological problems, life difficulties and school
absence (Table 3).
May be this sums up the paper. They take children who parents say their child was "feeling tired or felt she/he had no energy” which resulted in not doing stuff and then label them as having CFS. They then correlate this with "psychological problems, life difficulties and school absence". If a teenager was depressed then they would seem to fit the "CFS" category and then have "psychological problems".
After imputation, depressive symptoms (SMFQ score ≥11) were reportedby 67.4% of children with CFS, compared to 15.3% in those without CFS, and children with CFS had 11-fold higher odds of depressive symptoms (OR 11.0 (5.92, 20.4)), compared with children without CFS (Table 3). The
So basically they stick a CFS label on teenagers with fatigue and the accredit symptoms to CFS.
Or they do give an alternative view
The imputed prevalence of CFS of ≥3 and ≥6 months’
13
duration, if all children with depressive symptoms 287 were classified as not having CFS, was
288 0.90% (0.60%, 1.20%) and 0.60% (0.37%, 0.84%), respectively
So those are possibly better figures but would still cover other issues/diseases
Of course social problems could lead to a level of fatigue or statement of such. Or perhaps teenagers say 'i'm too tired for that' when actually they are just not interested in their old hobby or sporting activity but don't want to say that to their parents who were keen on it.