“…Eight studies were on liver transplant, three on kidney transplant, and two on cardiac transplantation. Three studies primarily focused on cannabis use [13,23], one on injection drug use (IDU) [16], three studies did not present data on individual substances [18,[24][25], and the others presented data on multiple substances. In the overall cohort, any illicit drug was used by 35% at some point in time, most frequently cannabis (31%), amphetamine (16%), heroin (5%), cocaine, inhalants, and hallucinogens (8% each)…”