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1) 🇩🇪 There's a new randomised trial of cognitive behavioural therapy (CBT) for Long Covid, from the Johannes Gutenberg University Mainz in Germany. It claims that CBT lowered fatigue but it has the usual fatal limitations that make the results unreliable.

2) First major error: there was no control intervention. The control group was simply put on a waiting list to receive CBT for 16 weeks. This creates an enormous bias so that the results are likely distorted by expectancy and placebo effects.

3) Second major error: all the outcomes were subjective questionnaires while patients nor therapists could be blinded. There was no actigraphy (step counter), exercise or fitness tests, employment rates, healthcare use, or any other objective outcome.

4) If people in the trial know what the intervention is and you use subjective questionnaires, than the results will again be distorted by placebo effects and response bias. Patients will respond to what they suspect the therapists/researchers want to hear.

5) CBT also targets cognitions and interpretation of symptoms, and patients have close contact with therapists for multiple sessions. This makes this treatment highly likely to cause distorted results on symptom questionnaires.

6) The third major error is that the authors used 5 primary outcomes and didn't control for multiple comparisons. Only one of these, the fatigue severity scale (FSS), had a p-value (0.045) that was marginally below the significance threshold of 0.05.

7) With correction, however, none of the results would be statistically significant, meaning the difference could simply have occurred by chance. The plot below shows the treatment effect for the FSS scale, which wasn't anything unusual.

8 ) Proponents of CBT will likely use this study as confirmation that the treatment works (another positive RCT!), but it really doesn't. This looks more like a promo-article that doesn't contribute to the scientific discussion, but helps to push a narrative in the literature.

9) One notable result from the study is that 94% of LC patients had PEM using the DePaul Symptom Questionnaire-2, which is very high. Questions have been raised if this scale actually measures PEM and not something more benign, such as exercise intolerance.