What drug is most commonly linked to hallucinations and flashbacks?

LSD, or lysergic acid diethylamide, is renowned for its potent psychoactive effects, including hallucinations and altered perceptions of reality. This substance affects serotonin receptors in the brain, leading to significant changes in mood, cognition, and sensory perception. One of the hallmark experiences associated with LSD use is the occurrence of "flashbacks," which are spontaneous recurrences of the effects of the drug that can occur days, weeks, or even months after the initial use. These flashbacks, sometimes referred to as hallucinogen persisting perception disorder (HPPD), can be distressing and are particularly linked to users of LSD. While other substances can cause hallucinations, LSD is the most commonly associated with both hallucinations during intoxication and the potential for flashbacks afterward.