Simultaneous polysubstance use among Danish 3,4-methylenedioxymethamphetamine and hallucinogen users: combination patterns and proposed biological bases.

OBJECTIVE To describe patterns of simultaneous polysubstance use (SPU) among Danish 3,4-methylenedioxymethamphetamine (MDMA) ("Ecstasy") and hallucinogen users. METHODS A cross-sectional survey of 98 active MDMA and/or hallucinogen users recruited through homepage advertisements, flyers, and word of mouth in Denmark. Lifetime and recent substance use and SPU at last recalled use was described by structured interviews. Hair samples from a subset of participants were analyzed for MDMA. RESULTS The participants had used an average of 12.6 (95% confidence interval: 11.7-13.4) psychoactive substances during their lifetime. SPU was prevalent among MDMA, d-lysergic acid diethylamide (LSD), and psilocybin users, in particular with alcohol and cannabis. Among MDMA users, 69% had combined MDMA with amphetamines, 56% with hallucinogens, and 47% with cocaine. At last recalled use, MDMA was taken with 2.1 ± 1.2 substances in 32 different combinations. The participants preferred specific drug combinations and named several, which in their experience enhanced or counteracted each other. Alcohol and cannabis were typically used before, during, and after MDMA, LSD, and psilocybin, whereas amphetamines were predominantly taken before these substances. When LSD was combined with MDMA, the majority took MDMA after LSD. CONCLUSIONS Simultaneous polysubstance use was common among Danish MDMA and hallucinogen users, and patterns of preferred substance combinations were evident.