The Acid Flashback Revealed

A simple pair of sunglasses may be all that’s needed to ward off the rare but disconcerting phenomenon generally referred to as an acid flashback. “Hallucinogen persisting perception disorder” or HPPD, is defined as the re-experiencing of visual symptoms first experienced under the influence of a hallucinogen, in a way that causes anxiety and distress. This includes such symptoms as geometric hallucinations, false perceptions of movement, flashes of color, intensified colors, tracer-like trails, after images, and halos around objects. Other drugs like Ecstasy sometimes produce the effect as well.

It's clear to researchers John Halpern and Harrison Pope, Jr. that flashbacks have something in common with another disorder we know mostly by its acronym—PTSD, or post-traumatic stress disorder. For one thing, they both occur weeks or months after the original experience. In an article for Drug and Alcohol Dependence, Halpern and Pope note that in the case of LSD, the classic “bad trip” may qualify as a traumatic incident capable of igniting PTSD-like symptoms. Curiously, the authors found that “individuals administered LSD in therapeutic or research settings are far less likely to develop hallucinogen persisting perception disorder than individuals using LSD illicitly.” The best medicine? “Reassurance,” says Halpern. The symptoms typically resolve without treatment within a few months.  However, people suffering flashbacks sometimes find that bright light intensifies the symptoms. “Sunglasses definitely are helpful,” says Halpern.