A session just talking to somebody about being ill/the problems it brings etc. , rather than a session with a CBT therapist would be the best control for CBT. (it's not within-subject so not perfect control) Just make the sessions in the same settings and of the same duration. The only difference being the CBT or just chatting about the illness. (of course, that would put a complete kybosh on CBT, so would never be considered) A pill would never be considered a proper control for a behavioural intervention, such as therapy. To control for GET would be harder. It would be best compared to pacing, because both involve a degree of activity. I don't know what is involved with their version of pacing, but it's not ours, is it?