A patient with no history of LSD ingestion reported 14 of 16 visual symptoms characteristic of LSD flashbacks, including persistent visual distortions that began during a near-psychotic episode at age 17 and continued for 20 years with decreased frequency. Short trials of two neuroleptics (thiothixene and trifluoperazine hydrochloride) increased her symptoms. This case suggests that the visual phenomenology associated with LSD flashbacks can occur without prior hallucinogen exposure, arising instead from a psychotic episode.
The author responds to a suggestion that visual disturbances described in LSD users also occur in non-users. While a careful history is key to diagnosing LSD flashback syndrome, clinicians must first rule out more dangerous and treatable causes of visual disturbances, including brain lesions, infections, metabolic issues, deliria, dementias, sleep disturbances, and eye disorders. In the author's study, two non-LSD-using control subjects reported eight and nine types of visual disturbances with no diagnostic explanation found, while other controls reported five or fewer. This suggests that some individuals without LSD use experience multiple unexplained visual disturbances.
Among college-age subjects given 160 μg/kg psilocybin under conditions of sensory attenuation, only those with high variability in predrug handwriting area (the "variable" subjects) showed a significant decrease in mean pulse rate and increase in handwriting area. These variable subjects also reported consistently more intense drug-induced experiences than those with low variability. The degree of variability on perceptual-behavioral measures, such as the standard deviation of handwriting area, predicts the intensity of the ensuing drug experience.