Research aims to systematically investigate and study important questions in order to increase knowledge through the discovery of new facts. As preceding chapters have shown, much is known about the burden of disease and injuries in adolescence and the risk factors for future adult burden, effective health interventions, and prioritizing and implementing interventions in adolescent health and well-being programmes. Still, further research on adolescent health and well-being is essential to achieve the ambitious health-related SDGs. Key areas include developing evidence on which interventions should be implemented and under what conditions (the what and the how of programming for adolescent health and well-being). Emerging threats and opportunities, such as harmful use of digital media, climate change and pandemic risk, also need investments in research.

Research focused on child and adolescent development has been conducted primarily in the HICs of North America and Western Europe, neglecting developmental issues that are unique to the majority, who live in LMICs. This leaves a gap in basic research addressing normative development during adolescence in a range of cultural, social and environmental contexts. Interdisciplinary approaches and collaborations between academic researchers and those working in applied settings offer much potential to fill such knowledge gaps. 

To strengthen programmes and policy, further investment is needed to unpack the challenges and opportunities of multisectoral programmes for adolescents. Conceptual and measurement advances are needed to further study adolescent voice and agency, connectedness, civic and social participation and engagement. In addition, while household surveys often capture the situation of adolescents 15 years and older, 10- to 14-year-olds are not adequately covered. Last, but not least, inclusion should be a priority for data collection and research. A recent review of evidence gap maps noted that fewer than one in every five studies analysed gender as a variable of interest. Only 3% of studies addressed disability. 

Unfortunately, relative to the research capacity for maternal, newborn and child health, adolescent research capacity is weak, especially in LMICs where it is needed most. Investment to strengthen research capacity will need to involve multiple disciplines. Such research is likely to pay a substantial return on investment.

Undeniably, the number of important research questions is large; investments will need to be prioritized. Over the last 10 years, WHO has conducted priority-setting exercises in adolescent health and well-being to help countries direct their research investments. These exercises use versions of the Child Health and Nutrition Research Institute (CHNRI) methodology, in which experts propose potential research questions and then score them based on clarity, answerability, importance, potential for implementation and relevance for equity. Exercises showed that priorities have shifted away from basic questions on the prevalence of specific health conditions towards questions on scaling up existing interventions and testing the effectiveness of new ones.