[Tobacco and cannabis in psychiatry: nursing practice].

The treatment of tobacco and cannabis use in psychiatry is a major public health issue. These substances, used to manage psychiatric symptoms, aggravate pre-existing disorders and reduce the effectiveness of treatments. Nurses offer comprehensive, integrated support that takes into account dual pathology, combining an experiential approach, risk and harm reduction, early detection and brief intervention, and support for change, while collaborating with various specialized stakeholders.