The survey is based on DSM-5 criteria, hence it includes under the "Hallucinogen" group several substances which are not classic serotonergic psychedelics, and excludes MDMA which is categorized under "Club drugs".
Substances included in the study are:
Lysergic Acid Diethylamide (LSD), peyote, mescaline, psilocybin, anticholinergics, N,N-Dimethyltryptamine (DMT), 2,5-Dimethoxy-4-methylamphetamine (DOM), Dimethoxybromoamphetamine (DOB), Salvia divinorum, dextromethorphan, and phencyclidine.
Based on previous epidemiological studies, a significant majority of "hallucinogen" users (as defined above) are in fact users of classic serotonergic psychedelics (such as LSD, psilocybin, mescaline and DMT).