From repeated use?

I knew at least one person who was a tripped out mess every time I saw them.

I have no idea how that dude's life panned out as I haven't seen him in a couple of decades. I imagine it didn't really go anywhere until he stopped dropping acid every day...

Some people report HPPD from repeated use.

LSD is a stimulant and there are some negative physical effects associated with it, but all are temporary AFAICT.

a bad trip, psychosis and maybe even PTSD. I take LSD and other psychedelics on a regular basis and if you know how to prepare for a trip then bad experiences are unlikely. but a bad experience on LSD can be really unsettling. this concept of set and setting is true after all.