I once had a single, very high dose Psilocybin experience which lead to a lasting change that was very much for the worse.

Having had my perception of reality profoundly changed by the experience I began to question my senses on a regular basis, with associated anxiety and panic. Then there were also the nightmares where I was tripping, would wake up, have something weird / trippy happen have a "world is ending" anxiety attack complete with ears ringing so loudly its painful. Then I'd wake up from that, with similar results, only to wake up from that. Never really sure if I was fully awake or not.

Thankfully after 18 months or so, it went away.

Of course, your mileage my vary :-)

I personally am in favour of this type of research but just wanted to share my experience. Its not all beer and skittles!

To echo that point... my pure-shroom experiences were generally positive, but one time mixing with MDMA resulted in a very strong experience that by the end involved some paranoia about keeping my thoughts and public utterances separate. That paranoia would occasionally mildly recur the next year or so. That's now many years ago, but I still wonder if crazy street people talking to themselves just mixed too many things, too many times creating permanent confusion.

Yes, listen to this man. If you are prone to depression/anxiety/paranoia/negativity do not try hallucinogenics.

Otherwise, it can be a positively life altering experience.

Not fun :( I've had two months of depersonalization after a psylocybin take. Lowered intellect, unability to stop the flow of thoughts, anxiety of being schizophrenic, no emotions except for art, seeing a monster when looking at the mirror. Sensorial defects became readily apparent which is annoying but useful. I still see coloured points sometimes.

The next experience was entirely positive though (outdoor, friends).