Substance use in young people (aged 10–24 years) is a significant health and social problem throughout the world. The 2013 Global Burden of Disease estimated that substance use among young men was responsible for 14% of total health burden. Recent findings have underlined the neurobiological vulnerability of young adults and the impact of co-occurring substance use disorders and mental health problems that emerge in adolescence. Adolescence is the peak period for initiation of substance use. A consistent finding from the international literature is that levels and frequency of use of drugs, alcohol, and tobacco begin to increase in mid-adolescence and peak in very early adulthood. These are key periods of change, cognitive and emotional development, and transitioning into employment, stable relationships, and parenthood.

Preventing, delaying or reducing young people’s use of alcohol and other drugs is a major part of all governments’ drug strategies. Unlike other interventions, which might be resisted for moral or ideological reasons, prevention programmes are widely supported by the general public. Yet, unlike evidence-based harm reduction policies that often face sustained opposition, many of the most common prevention programmes are supported by a very narrow evidence base. This is because most prevention options in place have not been evaluated. Those that have been evaluated are largely concentrated in school settings that facilitate research opportunities and the possibility to collect follow-up information on the participants in these programmes. It is an enormously difficult task to influence behaviour at the time of life when people go through rapid changes in neurobehavioural and psychosocial functioning. Entering early adulthood is a complex, challenging, and often bewildering experience for young people. Establishing a scientific approach to enable young people to navigate the many risks they face is probably the most difficult, and most important, task faced by decision-makers working on substance use policies.

This issue of Drugnet Ireland highlights some recent interesting developments in prevention studies. There is a strong correlation between diagnosed psychiatric disorder and substance use. Attention deficit hyperactivity disorder (ADHD), conduct, and personality disorder as well as affective disorders have been linked to increased substance use in adolescence. A systematic review published in 2020 finds that school-based programmes applying interventions based on positive psychology interventions can have positive effects on psychological wellbeing, and their inclusion in the school curriculum should be explored. Bullying is an important risk factor for poor mental health outcomes, and two 2020 reviews have found a small but significant effect from evaluations of anti-bullying interventions.

Prevention science has made great progress. Despite this, and the increasing availability of high-quality evidence in the field, it can be difficult for stakeholders to decide on the best approach. Selecting and implementing prevention interventions is a major undertaking and decisions can be difficult to reverse if new evidence emerges challenging the efficacy of programmes already in place. Initiatives like the Xchange Registry, described in an article in this issue, provide the type of valuable scientific and experiential information to support informed decision-making and more effective responses to substance use among young people.