Data from studies on specific cannabis users support high internal consistency for the SDS (Table 2). This holds true for samples of long-term cannabis users (at least 10 years with weekly use) [26], schizophrenia patients (cannabis use in the last 12 months) [20] and regular users of cocaine [19]. Additionally, a study of out-patients with alcohol dependence found good internal consistency for the CUDIT [13]. Item-total correlations for nine out of ten individual items were moderate to high, but could not be calculated for item 9 (injuries) as there were no positive responses to this question.
