Introduction Hallucinogen Persisting Perception Disorder (HPPD) is a syndrome characterized by prolonged or reoccurring perceptual symptoms, reminiscent of acute hallucinogen effects. HPPD was associated with a broader range of LSD (lysergic acid diethylamide)-like substances, including cannabis, MDMA (methylenedioxymethamphetamine), psilocybin, mescaline and other psychostimulants....