[How to detect teenagers' cannabis use and what needs to be done?].

Adolescence is a period of confrontation and initiation to psychoactives drugs. Teenager's substance disorder remains an important concern for families and public authorities. The seriousness of consequences due to cannabis use, both on the health and social points, depends on the age of first use, the duration of use and the user himself. Teenagers, who do not often request to be taken care, are a population who has difficulty to access to medical treatment, even if the offer of medical treatment has increased. It is necessary to develop an early detection among vulnerable populations like teenagers, to train first aid operators to early detection strategies, as well as to increase the knowledge of the care system to improve teenagers' orientation in the care system.