This is the first of three articles that will look at the issue of adolescent substance use. This article introduces different substances and how they are used. The second article will focus on adolescent substance use, the harm it can cause and the best prevention methods available. The final article will focus on treatment of adolescent substance use. This article starts with an overview of categories of substances followed by a brief overview of how substances interact with the body. Specific substances that are most relevant to those working with adolescents in Ireland today are then discussed. Alcohol and cannabis are the two most frequently used substances, while cocaine and nitrous oxide are also discussed as they have received significant media attention in recent years....

....Summary: As this article highlights, substance use is complicated. There are many substances available, but most of adolescent substance use consists of alcohol and cannabis. It is rare to encounter someone who is using another substance and not also using alcohol or cannabis. While alcohol use is common, it does not mean that drinking every week is the norm. Likewise, cannabis has only been tried by about one in five teenagers and so we should avoid an overly accepting or normalising view. The next article will discuss a little more about why adolescent substance use is so concerning and then talk about how substance use can be prevented.