> Have you personally ever taken LSD and actually suffered flashbacks? If yes, how bad were they?
No, of course not. I am a law-abiding citizen who believes in the rule of law, and I would never consider breaking it. I did, however, have some ruffian, rebellious, criminal friends--albeit, the type of criminal who goes to MIT or who goes on to get a PhD in Math--in college, and they told me what it was like.
Re flashbacks, they told me that no that didn't happen. They did, however, perceive textures on real objects (e.g., the kind in carpets or detailed wallpaper) continue to "breathe" and undulate a bit for the next year or two. (My guess is that such textures are always undulating a bit, perceptually, only you train yourself not to notice it.)
It was the actual experience, I am told, that could be very grueling. I.e., imagine watching "The Exorcist" alone in a big haunted house, only you can't turn it off, and you can't stop watching it, because if you close your eyes, it's now being projected in 3D onto the insides of your eyelids. Only multiply this by 1,000X. I imagine that this kind of stress could have lingering effects for those who already have difficulty dealing with it.
Despite the scariness of the experience, the friends who experienced it this way said the experience was still very worthwhile, and they wouldn't change anything. They just wouldn't necessarily do it again anytime soon.
Some friends didn't find it scary; they just found it fun.
One acquaintance went crazy shortly thereafter, but he was probably teetering on the edge to begin with. Friends who did it dozens of times, were invariably a bit strange ever thereafter, so I wouldn't recommend becoming too much of a rebel.
