LSD bought since the late '70's has not been dependable and that's an understatement. If you ingested 100% LSD you WOULD hallucinate. In the late '60's to mid '70's, LSD was true. Sugar cubes, Orange Sunshine, Windowpane, these disappeared by mid '70's. I gave up dosing at that point for the express reason that 'it' no longer worked, because 'it' wasn't true. The only dependable source post '70's was the inner loop of Dead bohemians. Most people who dosed post '70's weren't feeling effects of LSD, but any of the myriad useless alternatives.
I know several people who dosed literally thousands of times in their teens/twenties. They are 50's now and you wouldn't know they ever did. I also know one person who dosed once and has remained in a mental hospital for the last 35 years because of it. It comes down to you, not the substance. If you have baggage and are not emotionally stable, stay away from anything hallucinogenic. If you panic when you get lost physically, you'll panic when lost cerebrally.
LSD's greatest virtue was in psychological therapy. It worked like nothing else, and this valuable tool was no longer available past '65 due to illegality.
I think it's most prudent to say that no one should ever buy LSD today. There are far safer alternatives like mushrooms (NOT Amanita!). Psilocybe Cubensis is an extremely identifiable shroom found in cow pastures in the Southeast. The farmers with shotguns are far more dangerous than the steers and wild pigs though

. Psilocybe Cyanescens (and Psilocybe Baocystis to a lesser extent) are identifiable shrooms in the Pacific Northwest, and these two are very potent.
It's an interesting idea that LSD may increase IQ. I never considered that, but because of how LSD/Psilocybin(actually Psilocin) works - by taking the hypothalamus out of the loop - and because we know little of the complete process of cognition, we still really don't have a complete grasp of how/what can be, depending on the person. For me, it was never a 'spiritually enlightening" experience or an increase in perception or cognition. It was a mental amusement park with endless humor. It's different things to different people.