CANABICDoes a BI Conducted by General Practitioners Reduce Consumption of Canabis in 15 to 25 Years Old ?

General organisation of the study * Recruitment of the GP: 3 months (from December 2011 to March 2012) * Training of the intervention group GP during a one-day training, in March 2012, on 3 thematic: relationship between GP and adolescent, cannabis and BI; by an expert team * Inclusion period : 10 months (from April 2012 to January 2013). The included patients will be followed for 12 months. There are 3 follow up consultations at 3, 6 and 12 months. * First consultation used to the inclusion: Information to the patient and collection of the patient non opposition (without informing the intervention objectives in the control group). Evaluation of cannabis consumption, but also tobacco and alcohol consumption. Collection of the perception of cannabis by adolescents, and its impact on health. Inclusion criteriae : repetead users : 1 to 10 per month; regular users : 11 to 29 per month; daily users : 1 and more per day. In the IG : achievment of the BI with the adolescent. In each group, making appointment with the patient at 3 months • Follow up consultations : At 3, 6 and 12 months. Evaluation of cannabis consumption, but also tobacco and alcohol consumption. Collection of the perception of cannabis by adolescents, and its impact on health.