Despite these conceptual difficulties, there are different screening instruments used to measure negative consequences of cannabis use [11]. The Severity of Dependence Scale (SDS) [12] (see Appendix) is a 5-item scale that measures the degree of psychological dependence specifically related to the individuals' feeling of impaired control over and preoccupation and anxiety towards drug taking. The Cannabis Use Disorder Identification Test (CUDIT) [13] (see Appendix) screens for current cannabis use disorders (abuse or dependence) according to DSM-IV, whereas Problematic Use of Marijuana (PUM) [14] (see Appendix) measures ICD-10 harmful use along with problems in interpersonal relationships and psycho-physical functioning. Basically designed for adolescents or young adults, the Cannabis Abuse Screening Test (CAST) [15] (see Appendix) identifies patterns of cannabis use leading to negative consequences on a social or health level for the user himself or others. The major advantage of these four instruments is that they are brief and easy to administer. There are also other scales that measure cannabis-related problems, e. g. the Marijuana Screening Inventory (MSI) [16], the Substance Dependence Severity Scale (SDSS) [17], or the Cannabis Problems
