A research group associated with the SFB/TRR 289 investigated the effects of placebos in the area of sadness.
The result of the study was published in the Journal of Affective Disorders on May 1, 2022,under the title "Even when you know it is a placebo, you experience less sadness: First evidence from an experimental open-label placebo investigation".
You can read the full publication on ScienceDirect.