Self- or other-directed violent behaviours associated with alcohol and drug use are also significant problems. The period of adolescence and young adulthood is a time when violence is often given heightened expression. Any preventive measures envisaged must be flexible and tailored to the characteristics of young people and their environment. Understanding when and under what conditions violent behaviour typically occurs as a person develops can be helpful in planning interventions and policies for prevention that target the most critical age groups (WHO, 2002).