Elsevier

The Lancet Psychiatry

Volume 3, Issue 3, March 2016, Pages 265-279
The Lancet Psychiatry

Series
Why young people's substance use matters for global health

https://doi.org/10.1016/S2215-0366(16)00013-4Get rights and content

Summary

During puberty, when young people are completing their education, transitioning into employment, and forming longer-term intimate relationships, a shift in emotional regulation and an increase in risky behaviour, including substance use, is seen. This Series paper considers the potential effects of alcohol, tobacco, and illicit drug use during this period on: social, psychological, and health outcomes in adolescence and young adulthood; role transitions, and later health and social outcomes of regular substance use initiated in adolescence; and the offspring of young people who use substances. We sourced consistent support for causal relations between substance use and outcomes and evidence of biological plausibility from different but complementary research designs. Many adverse health and social outcomes have been associated with different types of substance use. The major challenge lies in deciding which are causal. Furthermore, qualitatively different harms are associated with different substances, differences in life stage when these harms occur, and the quality of evidence for different substances and health outcomes varies substantially. The preponderance of evidence comes from a few high-income countries, thus whether the same social and health outcomes would occur in other countries and cultures is unclear. Nonetheless, the number of harms that are causally related to substance use in young people warrant high-quality research design interventions to prevent or ameliorate these harms.

Introduction

The social transitions that occur during adolescence and young adulthood (age of 10–24 years) are essential for a young person's later life trajectories. As noted in the first paper1 of this Series on young people's substance use, this period of life is when substance use typically starts, and patterns of use become established.

The emotional shifts that accompany adolescence and young adulthood create opportunities and vulnerabilities.2 The process of puberty results in physical changes, shifts emotional regulation, and increases risky behaviours, such as substance use. Participation in risky behaviours occurs at a time when young people are completing their education, making a transition into employment, and forming long-term intimate relationships. These transitions can be disrupted by substance use and the development of substance use disorders, which often first emerge during adolescence. Substance use disorders often co-occur with, and complicate the course of, common mental disorders that can emerge in adolescence and young adulthood.3

In this Series paper, we consider the potential effects of substance use during this period on: social, psychological, and health outcomes during adolescence and young adulthood (ie, the results of intoxication and regular use); social and health outcomes during the life course (ie, outcomes of role transitions, and the effect of regular substance use initiated in adolescence and sustained over years or decades on health and social outcomes later in life); and the offspring of young people who use substances. We focus on the substances that are most often used in this period—alcohol, tobacco, and illicit drugs (particularly cannabis, amphetamines, cocaine, and opioids).1

Studies examining the possible outcomes of substance use in young people have been undertaken almost entirely in high-income countries. Whether these outcomes would be the same in low-income and middle-income countries, countries with very different cultures, and countries where the opportunities for young women substantially differ (panel 1) is unknown. These are all important areas for future investigation.

Section snippets

Adolescence and young adulthood

During the past 20 years researchers have discovered that neurodevelopment extends into the second and third decades of life.8 This realisation has heightened concerns about the neurobiological vulnerability of adolescents to the adverse effects of regular substance use on cognitive and emotional development.

Healthy brain development is essential for people to achieve their optimal cognitive abilities. The primary motor and sensory areas (eg, sensorimotor cortex and occipital pole) develop well

Assessing the effects of substance use in young people

The outcomes of substance use in young people might differ from those in adults for several reasons (panel 3). These are related to the unique social, cognitive, and physical changes that accompany adolescence and young adulthood.

Deciding which of the adverse outcomes associated with substance use are caused by the substance use is challenging because many of the risk factors for substance use and the adverse outcomes are shared. This complicates the task of attributing specific adverse

The potential risks of substance use in young people

The unique changes, transitions, and position of young people affect the potential outcomes of substance use. We can broadly describe three ways (triple risks) in which this might occur. First, during adolescence and young adulthood, acute intoxication and the short-term effects of regular heavy use can have adverse health and social effects. Second, substance use initiated during this period can have longer-term effects by disrupting social transitions to adulthood and entrenching sustained,

The increasing importance of substance use in the global health agenda for young people

Substance use is a substantial contributor to health burden during adolescence and young adulthood according to the Global Burden of Disease (GBD) studies.1 Substance use, in particular tobacco and alcohol, is increasing in many low-income and middle-income countries; however, the health and social effects of this increase might not be seen for some decades. In key UN agendas, the importance of addressing young people's substance use has been explicitly acknowledged. These include the

Research priorities

In this Series paper, we have highlighted major gaps in the evidence of the effects of substance use in adolescence and young adulthood. First, neuroscientific studies suggest that young people might be especially susceptible to the effects of substance use for many reasons.28 However, much of the research undertaken in people has not been of a sufficient standard to assess whether there are particularly raised risks of substance use at this age (as opposed to at older ages). More elaborate

Limitations of our search strategy

Although our search strategy was very wide in scope, the limitations of the strategy should be acknowledged. We did not search every database systematically, but concentrated on the largest two, with supplementary searches of others. Having said that, most of the remaining databases overlap, such that it is unlikely that we missed any major systematic or other literature reviews of the potential outcomes of substance use in young people. Additionally, when no reviews were located for a specific

Search strategy and selection criteria

We conducted a systematic review of PubMed and Web of Science for reports published in English between Jan 1, 1990, and April 23, 2015, with search terms pertaining to substance use, young people, and health and social outcomes (see appendix for search terms used). We searched for reviews of substance use in those aged 10–24 years. We screened Embase and PsycINFO for material not indexed by PubMed or Web of Science. Peer-reviewed articles were initially assessed on the basis of title and

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