Hallucinogen persisting perception disorder

Hallucinogen persisting perception disorder (H-PPD) is a medical condition where people continue to see, hear, or feel things that aren't really there, even after they have stopped taking a certain type of drug known as a hallucinogen. It's like having a really bad case of "seeing things" after taking a hallucinogen. Usually, the person experiences things like flashes of light, patterns in walls, or hearing voices. Sadly, these effects can last for months or even years and can be very difficult to manage.