Causes
The cause(s) of HPPD are not yet known. The most current neurological research indicates that HPPD symptoms may manifest from abnormalities in CNS function, following hallucinogen use. One theory derived from this research is that inhibitory mechanisms involved with sensory gating are disrupted.
In some cases, HPPD appears to have a sudden onset after a single drug experience, strongly suggesting the drug played a direct role in triggering symptoms. But in other cases, people report gradual worsening of symptoms with ongoing drug use. Drugs that have been associated with HPPD include LSD, 2C-E, 2C-I, 5-MeO-DiPT, MDA, MDMA, psilocybin, mescaline, diphenhydramine, PCP, synthetic cannabis, and high doses of dextromethorphan. Additionally there are anecdotal reports of the atypical psychedelic Salvia divinorum causing persisting symptoms consistent with HPPD.
Read more about this topic: Hallucinogen Persisting Perception Disorder