Cannabis use has been associated with a range of adverse effects that can be categorized in acute effects (e.g. impaired attention, memory and psychomotor performance, road accidents), chronic health effects (e.g. bronchitis, depression, dependence syndrome) and social problems such as low educational attainment [5]. Furthermore, people with unstable health conditions have been found to take cannabis to reduce symptoms of depression, psychopathology or psychosocial distress [6,7]. But while there are clear definitions and diagnostic criteria for cannabis dependence and abuse, there is no agreed-upon concept for cannabis-related problems or so called "problem cannabis use" for individuals experiencing such acute, chronic or social adverse consequences without fulfilling the criteria for dependence. However, in recent times, different researchers work on the elaboration of a sub-threshold category "problem use" [8,9]. A number of other indicators have been discussed, among them intensity of use [10], consumption patterns (early morning smoking, intake to facilitate sleeping, using pipes or other facilities) or treatment demands [8], but to date none has reached common acceptance.
