This is pretty solid evidence that CFS is not psychosomatic, given the difference in response between the control group and the group that received treatment. In case anyone was still unsure.
I think there's a flaw in your logic here: the fact that a drug that is targeting the immune system helps so much does not invalidate a psychological component in the etiology. It could be upstream (psychological stress could trigger the immune response that leads to CFS), it could be downstream (CFS leads to mental anguish given a patient's deviation from normative life-course, perceived isolation, and the historically-contested nature of the malady), or it could be both.
That said, a psychological / psychosomatic component wouldn't undermine its legitimacy in any way. Thankfully, I think we are entering an era in which psychological aspects of ailments are recognized as critical, beyond the control of the patient (e.g. not reflecting a lack of virtue or wherewithal on their part), and treatable.
I'm in the bio-pyscho-social camp, I believe the three elements work in concert to keep the show going, over stressing all three consistently does seem to correlate with an immune malfunction, and treatments that approach only 1 of the three 'prongs' appear less successful than those that approach all three.
I've not read Cho but in 2011 trial none of the control group given placebos experienced relief against most of those given the drug. That seems like not much of a placebo response to me.
The 2011 study was negative in its primary end-point. If you look at the results you'll see that the divergence between active and placebo groups only happened after the researchers unblinded the data at the 3 month point. Although they say that the patients were still blinded until the end, there are still some question marks about the study.
