Do blind people hallucinate on LSD?

I’ve just found a remarkable 1963 study [pdf] from the Archives of Opthalmology in which 24 blind participants took LSD to see if they could experience visual hallucinations.

It turns out, they can, although this seems largely to be the case in blind people who had several years of sight to begin with, but who later lost their vision.

Those blind from a very early age (younger than two years-old) did not report visual hallucinations, probably because they never had enough visual experience to shape a fully-functioning visual system when their brain was still developing.

"It is evident that a normal retina is not needed for the occurrence of LSD-induced visual experiences. These visual experiences do not seem to differ from the hallucinations reported by normal subjects after LSD.

Such phenomena occurred only in blind subjects who reported prior visual activity. The drug increased the frequency of visual events such as spots, lights, dots, and flickers. However, the complex visual experiences reported by 3 subjects after LSD did not occur after placebo or in ordinary experience.

It is interesting to note that duration of blindness was not related to the occurrence of visual hallucinations; nor was intelligence, acuity of visual memory, or use of visual imagery in speech."

I mentioned in an earlier post on auditory hallucinations in deaf people that I’d heard rumours of studies on LSD in blind people but never found any reports. This study is not the only one it seems. The paper reviews several other studies in the same area.

[Thanks Sam Hell!]