Please help! what is the occurrence of hallucinogen persisting perception disorder?

Seen with bath salts: But it is rare. Several researchers looked into the stories that became common in the 60s and 70s about people having "flashbacks" to hallucinatory experiences, and found that most of the people with that history had underlying psychotic disorders like schizophrenia. It has been reported in users of hallucinogens but is probably quite rare. If this is you, see a psychiatrist trained in addiction.