The first problem with this myth is that "insane" isn't a real legal term, except in rare cases of pleading the insanity defense (the media love to latch onto such cases with their little lamprey mouths, but in actuality they don't occur very often). Plus, there's no scientifically accepted mental disorder that can be diagnosed simply based on past drug use.
The second problem with this myth is that LSD can't make you insane. In a 1960 study, LSD was given to 2,000 people, half of whom were known to be either mentally ill or genetically predisposed to mental illness. Only 0.13 percent of the test subjects exhibited any form of psychotic behavior, and nearly all of those who did were in the "already kind of crazy" bucket. Scientists hypothesized that LSD doesn't "cause" psychoses, it triggers them -- meaning that the people exhibiting psychotic behavior already had underlying mental problems. Even so, many of the horror stories you've heard about people jumping off the high dive at the Crazytown pool after tripping on acid are completely made up.
Creatas Images/Creatas/Getty Images
That's not what crazy looks like. It's what we picture when we're doing our mandatory LSD at Cracked.