to a cluster analysis that resulted in five clusters comprising 41 of the 50 items (see Evans and Levin, 2002). The “Personality Traits” cluster consisted of 8 items related to personality traits (e.g. “I feel friendly”), the “Physical Symptoms” cluster consisted of 12 items related to physical symptoms (e.g. “I have a headache”), the “Bad Effects” cluster consisted of 9 items related to negative subjective effects (e.g. “I feel miserable”), the “Elevated Mood” cluster consisted of 6 items related to positive drug effects (e.g. “I feel high”) and the “Sedation” cluster consisted of 4 items related to sedation (e.g. “I feel tired”). During each assessment battery after dosing, participants also completed a Drug Effect Questionnaire (DEQ; see Evans et al., 2000 for details).
