Health - Does LSD affect IQ

[rainsong]

Sorry if this has already been discussed, but I did a pretty thorough search that came up with no results. I was wondering if there was any proof of LSD affecting IQ. I have heard of people being "permafried" and I have also heard from a friend who thinks he was a little bit "brain damaged" after a 1000mcg trip. If no one knows of any studies, it would be appreciated if anyone could tell me anything they think about the possibilities of LSD's effect on intelligence (ie. amount that has to be taken/minimum amount of trips that will result in damage to the brain). I realize that LSD may not lower intelligence at all in some amounts and could possibly increase it what with the "mind-expanding" aspects and all, but I am under the impression that there reaches a point where it can negatively impact the mind.

Anyway I am just trying to get an idea of the risks to intelligence (I am already comfortable with the risks of HPPD, flashbacks, etc.) before I have my first LSD trip.