While we know that many people will experiment with drugs like amphetamines and ecstasy in their late teens and early twenties, we only have a limited understanding of why some people moderate or cease their use after a period of time, while for others the level of use will escalate and will have a negative impact on their lives.

One question relates to the effects of public policy. In what ways do public measures such as health campaigns, treatment services and law enforcement impact on drug use behaviour? Public measures such as changes in the law (e.g. the introduction of cigarette smoking bans) can modify the behaviour of an individual without that individual ever experiencing the enforcement of that law. In addition, treatment services (e.g. counselling, detoxification) provide important assistance for people who are drug dependent. Sometimes people charged with a drug-related offence are diverted to treatment services.

However, only a minority of drug users are directly affected by public measures such as treatment and law enforcement activities. Furthermore, some people will knowingly break drug laws even though they might be generally law-abiding. What then, aside from public policy, are some of the important factors that influence people’s decisions regarding the use of drugs? Both personal and environmental factors can play a role in drug use behaviour.

Early adulthood is a key period in which to study these factors. During this period people are often experimenting with drugs for the first time, and are also developing attitudes and beliefs that will inform their future decisions. Factors such as family background, the quality of friendships, and engagement in education and employment can profoundly influence the behaviour of young adults. This study is concerned with identifying and understanding the key factors that explain why the outcomes of amphetamine use are markedly different for different people.