The use of both legal and illegal drugs among teenagers and young adults is widespread. Teenagers are likely to experiment, test boundaries and take risks. Smoking, drinking and trying drugs are some of the most common ways in which many young people do this. However, substance misuse is also one of the most common risks to a young person’s health and development. All drugs have the potential to cause harm, some can be addictive, and using drugs in combination can increase the risks. Legal drugs such as alcohol and tobacco can be very addictive. Illegal drugs include cannabis, cocaine, ecstasy and heroin.