It is little-known but clearly established knowledge that psychedelics are very potent at curbing inflammation, including inflammation in the central nervous system. Inflammation in the CNS and feeling bad are highly correlated.

For more information, see this paper for instance – Psychedelics and Immunomodulation by Dr. Attila Szabo of the University of Norway, published in 2015: https://doi.org/10.3389%2Ffimmu.2015.00358