Brief interventions are recommended for adults with alcohol or drug misuse, especially those with minimal contact with services. They can be conducted in primary care, emergency departments, prisons, and other settings. Brief interventions delivered opportunistically for alcohol misuse have been shown to be effective, while evidence is less strong for drug misuse. Extended brief interventions may be needed for those resistant to brief interventions. Dependence requires a full assessment, and brief interventions are more effective with multiple sessions for some groups like young people.