Introduction

A clear social change over the second half of the 20th century was the increase in the proportion of young people using alcohol and different kinds of other drugs, which have become a conspicuous part of the social landscape. The shifting pattern of use by young people and the possible links to trends in mental health problems are the subject of this chapter.

The interface between adolescence and substance use is particularly salient. To start with, adolescence is generally when people begin using substances. It is thus a particularly interesting period with respect to the natural history of substance use; when and how people start is, we know from research, important to their later outcomes, so adolescence constitutes a critical period (Mirza and Mirza, 2008).

Second, brain and hormonal changes in adolescence have special significance when we are considering the impact of drugs. Recent research on adolescent brain development points out how much basic building work is still being undertaken during the teenage years, and mind-altering substances could potentially have different effects at this stage compared with other age groups (Morris and Wagner, 2007; Windle et al, 2008). There is some evidence that adolescent brains show increased sensitivity to immediate rewards and different perspectives on risk taking, making drug use potentially more dangerous (Spear and Varlinskaya, 2005). Again, this is important to a consideration of trends and particularly to the potential for a relationship with mental health symptoms.

Third, the social challenges of identity development, the establishment of autonomy and the particular focus on peer groups may also all create a period of extra vulnerability to drug and alcohol use in adolescence. The social structures that, in their own ways, shape the initiation of young people into the world of substance use may have changed over time.

Research questions

Despite the existence of quite a lot of data, and much commentary, it still seemed that there was a need for an objective evaluation of the long-term time trends in substance use with a clear focus on the adolescent years, and also an evaluation of the extent of any potential causal relationship with adolescent mental health symptoms.