I think there's a placebo effect that is related strictly to the human interaction effect - you go to see a doctor, the doctor pays attention to you, you feel l

I think there's a placebo effect that is related strictly to the human interaction effect - you go to see a doctor, the doctor pays attention to you, you feel like people care about what happens to you, and so your mood improves. I have no idea how to quantify this effect (send pills in the mail with no human interaction?) but it appears to be significant in some cases of depression.