With all the praise of self-experiments (or experiments on a dedicated core group), there is this fact: we know that even a single use of a psychedelic drug may

With all the praise of self-experiments (or experiments on a dedicated core group), there is this fact: we know that even a single use of a psychedelic drug may be "a life-changing experience". We also know that some substances may cause irreversible changes in the brain (e.g. glue-sniffing). So IMHO it doesn't sound like a rigorous science, who knows what changes those countless tests had caused and how those changes affected subsequent tests.