We compared characteristics of schizophrenia patients with prior LSD use who developed hallucinogen persisting perception disorder (SCH+HPPD) with those who did not (SCH-HPPD). Data were collected for 37 subjects in the SCH+HPPD group and 43 subjects in the SCH-HPPD group. Socio-demographics and positive symptom scores were similar between groups. Individuals in the SCHIZO+HPPD group scored...