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From neuroscience, we know that adolescence is a dynamic phase of brain development, profoundly modulated by environmental factors, including social determinants such as gender norms.6 We know that, after the onset of puberty, the risk of depressive disorders increases substantially among girls, who will remain 1·5 to 2 times more likely than boys to be diagnosed with depression, a gap that will persist over their life course.6 For girls who experience victimisation in early adolescence, mental health outcomes are particularly adverse.7 From social science research, we understand that adolescents experience increased gender role differentiation and, in many cases, exaggerated forms of gender-based discrimination.

Better childhood health and nutrition, extensions to education, delays in family formation, and new technologies offer the possibility of this being the healthiest generation of adolescents ever. But these are also the ages when new and different health problems related to the onset of sexual activity, emotional control, and behaviour typically emerge. Global trends include those promoting unhealthy lifestyles and commodities, the crisis of youth unemployment, less family stability, environmental degradation, armed conflict, and mass migration, all of which pose major threats to adolescent health and wellbeing.

[...]few studies and interventions disaggregate the modes of transmission when addressing the needs of adolescents for prevention and treatment of HIV.3 There are limited population-level data for HIV transmission in adolescents through injecting drug use, although, based on existing data, we assume that at a global level such transmission is likely to be minimal.4,5 Sexual transmission requires further investigation. Estimates suggest that 10–12% of children in low-income and middle-income countries have engaged in sexual activity before the age of 15 years,7 but there are no population-level data on sexual transmission of HIV in this population, which comprises some 557 million individuals globally.8 Existing data are insufficient to estimate accurately the number of younger adolescents who newly acquire HIV and the proportion of younger or all adolescents who acquire it through sexual transmission. Vertical transmission has already contributed to more than half a million adolescents aged 15–19 years currently living with HIV worldwide,9 and these adolescents have unique needs for care, treatment, and sexual and reproductive health services.3 But it is important to understand that, particularly in some of the regions with the highest HIV prevalence, girls—starting in the years for which data were not collected—are at increased vulnerability to sexual transmission of the virus.

Young people's health has emerged as a neglected yet pressing issue in global development. Changing patterns of young people's health have the potential to undermine future population health as well as global economic development unless timely and effective strategies are put into place. We report the past, present, and anticipated burden of disease in young people aged 10–24 years from 1990 to 2013 using data on mortality, disability, injuries, and health risk factors. The Global Burden of Disease Study 2013 (GBD 2013) includes annual assessments for 188 countries from 1990 to 2013, covering 306 diseases and injuries, 1233 sequelae, and 79 risk factors. We used the comparative risk assessment approach to assess how much of the burden of disease reported in a given year can be attributed to past exposure to a risk. We estimated attributable burden by comparing observed health outcomes with those that would have been observed if an alternative or counterfactual level of exposure had occurred in the past. We applied the same method to previous years to allow comparisons from 1990 to 2013. We cross-tabulated the quantiles of disability-adjusted life-years (DALYs) by quintiles of DALYs annual increase from 1990 to 2013 to show rates of DALYs increase by burden. We used the GBD 2013 hierarchy of causes that organises 306 diseases and injuries into four levels of classification. Level one distinguishes three broad categories: first, communicable, maternal, neonatal, and nutritional disorders; second, non-communicable diseases; and third, injuries. Level two has 21 mutually exclusive and collectively exhaustive categories, level three has 163 categories, and level four has 254 categories. The leading causes of death in 2013 for young people aged 10–14 years were HIV/AIDS, road injuries, and drowning (25·2%), whereas transport injuries were the leading cause of death for ages 15–19 years (14·2%) and 20–24 years (15·6%). Maternal disorders were the highest cause of death for young women aged 20–24 years (17·1%) and the fourth highest for girls aged 15–19 years (11·5%) in 2013. Unsafe sex as a risk factor for DALYs increased from the 13th rank to the second for both sexes aged 15–19 years from 1990 to 2013. Alcohol misuse was the highest risk factor for DALYs (7·0% overall, 10·5% for males, and 2·7% for females) for young people aged 20–24 years, whereas drug use accounted for 2·7% (3·3% for males and 2·0% for females). The contribution of risk factors varied between and within countries. For example, for ages 20–24 years, drug use was highest in Qatar and accounted for 4·9% of DALYs, followed by 4·8% in the United Arab Emirates, whereas alcohol use was highest in Russia and accounted for 21·4%, followed by 21·0% in Belarus. Alcohol accounted for 9·0% (ranging from 4·2% in Hong Kong to 11·3% in Shandong) in China and 11·6% (ranging from 10·1% in Aguascalientes to 14·9% in Chihuahua) of DALYs in Mexico for young people aged 20–24 years. Alcohol and drug use in those aged 10–24 years had an annual rate of change of >1·0% from 1990 to 2013 and accounted for more than 3·1% of DALYs. Our findings call for increased efforts to improve health and reduce the burden of disease and risks for diseases in later life in young people. Moreover, because of the large variations between countries in risks and burden, a global approach to improve health during this important period of life will fail unless the particularities of each country are taken into account. Finally, our results call for a strategy to overcome the financial and technical barriers to adequately capture young people's health risk factors and their determinants in health information systems. Bill & Melinda Gates Foundation.

Thomas Verberne correctly notes that suicide has become the top ranked cause of death among 15-19-year-old girls, because of very welcome declines in maternal mortality in this age group. But we disagree that by shining a light on what have long been neglected issues, such as adolescent mental health, harmful gender norms, and adolescent mortality, we are somehow being misleading.

Many believe that linking population growth to the issue of climate change will help to place family planning back into the political realm as an urgent matter of national and environmental security. Others worry, however, that focusing on the environmental impacts of demographic change places at risk the hard-fought and long-developed global consensus that individual rights and empowerment are what matters most in fostering sustainable development and stabilizing population growth. This paper focuses on United States population policy. It presents a brief historical background and summarizes the state of scientific evidence regarding the impacts of population growth on climate change. It then analyzes some of the underlying ethical issues involved in advancing an advocacy argument around increasing family planning as a way to slow population growth and mitigating climate change. Finally, it recommends a way in which advocates can frame the connections between population growth and climate change in a just and ethical manner.

The United States has been a global leader in the international population arena for nearly fifty years, but the domestic policy debate around international population and reproductive health issues has been increasingly characterized by politicization and partisanship. This study explores the strategies and discourse that have been designed and employed to influence the direction and scope of U.S. international population policy over time, including those used by interest groups and members of the United States Congress themselves. Through a case history, qualitative interviews and a descriptive and interpretative content analysis of congressional debates, I assessed: (1) How interest groups and their issue definition, messages and strategies, have sought to influence United States international population policy over time. Specifically, have these messages and strategies influenced the positions of federal policymakers around international population policy? (2) How the gender and political party affiliation of members of Congress have influenced their support for international population programs. Are female legislators more likely than their male counterparts to pursue a pro- international reproductive health and rights agenda? (3) The tone of discourse employed by male and female members of Congress when speaking and voting on international reproductive health and rights issues on the House floor. My goal was to understand the quest by advocates on both sides of the international family planning issue to shift policy around this issue to their benefit. I find that the Religious Right has successfully managed to alter the debate about international family planning and reproductive health, including by deliberately conflating family planning with abortion. I find evidence of a growing partisan divide around these issues in the U.S. Congress, in both voting and speaking patterns. Finally, I conclude that female members of Congress engage more frequently and more positively on international family planning than do their male counterparts.

Petroni discusses the growing interest of the US public and policymakers, in the relationship between global population growth and climate change. She stresses that everyone must think very carefully before developing advocacy arguments that could invite disaster by triggering backlashes from all sides of the issue, setting international family planning back decades. She believes that a well, a thoughtful and deliberative dialogue around voluntary family planning's contribution to mitigating climate change can help better understand the significant role the US plays in the world.