In Europe, 12.1% of people aged from 15 to 34 state that they have consumed cannabis in the past year, vs. 16.7% in France and 24.1% for the United States . In France, cannabis is the most consumed illegal substance ; 39% of 15 to 16-year-olds  and 41.5% of 17-year-olds  have previously smoked cannabis. This consumption relates mainly to persons below 25 years of age with an average age of experimentation of 15 . Various levels of consumption are described: recent users (used at least once in the previous month), occasional (1 to 9 times per year), repeated (10 uses/year to 10 uses/month), regular (10 to 29 per month), and daily (at least once per day) . In France, in 2011, 24% of young people between 15 and 16 years of age and 25% of 17-year-olds were recent consumers vs. 15% and 25% in 2007 [3, 4].
Current data are clear about the risks of cannabis use: social and psychiatric risks, and highway accidents after smoking . There is no consensus over the treatment of adolescents who consume cannabis. In 2008, a review of the literature explored the out-patient strategies used: motivational interviewing (MI) seems to have positive results in terms of the reduction of consumption of cannabis by young people of less than 18 years of age . This was confirmed in 2013; cognitive-behavioural therapies, MI, and family therapy enable a reduction in the consumption of cannabis . MI was described by Miller and Rollnick in the early 1980’s , as a method of interaction centred on the patient intended to modify behaviours by working on the ambivalence of the patient, naturally generated by the prospect of change. The period of psychological and physical development of adolescence makes it a target that is particularly suited to this technique. Brief intervention (BI) is a technique for motivational counselling characterized by its short duration. Its criteria of effectiveness are described using the acronym FRAMES : Feedback, Responsibility, Advice, Menu, Empathy, Self-efficacy. In various European countries, trials have shown an effectiveness of BI on the consumption of alcohol [10, 11]. A Canadian and an Australian study have shown the acceptability of BI among consumers of cannabis [12, 13], and a trend towards a reduction in their consumption of cannabis [12, 13]. A trial showed a reduction in the frequency of consumption at 3 months among young consumers who had been given a BI . However, these studies were not undertaken in general medicine, but in facilities specialized in addiction or in school groups. A Swiss study showed good acceptability and feasibility of BI among general practitioners (GPs) and their young patients , without demonstrating its effectiveness.
The 2008 report by the World Organization of Family Doctors on mental health  stressed that the treatment of addiction in primary healthcare is beneficial to the improvement of the overall health condition of patients and reduces the social and economic costs that are borne by patients and their carers. In France, the structure of primary healthcare is primarily based on GPs, who are the health professionals that are most consulted by adolescents. One in seven patients consulting general medicine is aged between 11 and 20 . Furthermore, for every seven patients, a GP sees one recent consumer during consultation . Recourse to the healthcare system increases alongside increased cannabis consumption .
The 2009–2012 European Union Action Plan on drugs  and the 2nd French Governmental Plan (2009–2011)  of the Inter-ministerial Mission for the Fight Against Drugs and Drug-Addiction prioritised prevention and the development of basic and clinical research. The training of primary healthcare doctors and other healthcare professionals for early identification was also a priority area.
However, a French study in 2011 showed that only 8% of GPs questioned adolescents on their consumption of cannabis , indicating that there are difficulties on the part of adolescents but also on the part of GPs in addressing this topic. In 2009, the authors carried out a qualitative survey intended to identify the barriers discouraging GPs from speaking about cannabis with young patients. The majority of the 24 GPs, grouped into three focus groups, did not speak about it because they felt insufficiently trained in the identification and the treatment of cannabis consumers, and did not know how to address the topic. They were even less at ease if they had known the adolescent for a long time. The illegal aspect of the substance was an additional barrier to discussion. They all lamented the trivialisation of consumption but also deemed that it was within the remit of the private life of a young patient.
The authors also undertook a qualitative study focusing on the reluctance of adolescents to discuss their health issues with their GP, and especially their consumption of cannabis . They were ambiguous with their GP, who they perceived to be both moralizing and the person who is responsible for addressing the topic. They were more comfortable speaking about it if they had known the GP for a long time and if they were alone during the consultation.
The authors hypothesize that in France, a BI in general medicine could enable identification of cannabis consumption in adolescents and propose early treatment, intended to reduce their consumption.
The main objective of the CANABIC study is to measure the effect at 12 months of a BI by GPs on cannabis consumption among recent user adolescents of 15 to 25 years of age. The secondary objectives relate to the variations in intermediate cannabis consumption at 3 and 6 months, variation in consumption associated with other methods of consumption (e.g., “bongs”), variations in consumption associated with alcohol and tobacco, the change in the perception of adolescents regarding the effects of their cannabis consumption on their personal, social, and professional lives, and on driving following the consumption of cannabis.