“Conventional medical wisdom has long held that placebo effects depend on patients’ belief they are getting pharmacologically active medication. A paper published in the journal Pain is the first to demonstrate that patients who knowingly took a placebo in conjunction with traditional treatment for lower back pain saw more improvement than those given traditional treatment alone.” https://www.sciencedaily.com/releases/2016/10/161014214919.htm
Experiments to investigate the placebo effect are problematic. One of the main ways to research the placebo effect to get a cohort of sick people and give part of the group medicine and part of the group placebo and check for differences between the two groups. The people in the placebo group are not getting any medical help at all.