Twenty-one recreational polydrug users (age range: 17±34 years), were recruited into the study using the `snowball' technique (Solowij et al., 1992). All had used MDMA (3,4-methylenedioxymethamphetamine, or `Ecstasy'), LSD (lysergic acid diethylamide), and amphetamine, on dierent occasions. They completed modi®ed Pro®le of Mood States Questionnaires, to indicate their typical feeling states wh...