I've been grumbling about this for a while and it seems to me that we may place too much store in intention-to-treat analysis. I think it makes sense at a population level because in real life, people are going to drop out of therapies and they're NOT going to take the medicine. So at the level of writing clinical practice guidelines and estimating population-level health effects it's absolutely a valid and valuable method of assessing the treatment effect of therapy. However, I've been put out by several studies for therapies that ONLY report using ITT principles and don't give enough info to infer treatment effect in perfectly compliant patients. To me this is problematic, especially in the case of things like physical therapy, group therapy, or psychotherapy in which there is an additive effect of going to more sessions and/or completing a course. When a patient comes to me and asks about an intervention, or when I suggest one and he asks how effective it's going to be, I don't want to say "well, based on the fact that there's a 33% chance you're going to stop taking this drug or a 50% chance that you're not going to complete your mindfulness-based stress reduction class, you'll see an improvement of 30%". I'd like to be able to say "People who actually take their meds every day or complete the course see on average a 50% reduction in symptoms". Thoughts?