Conceptual pathways to HIV risk in Eastern and Southern Africa: An integrative perspective on the development of young people in contexts of social- structural vulnerability
Introduction
The transition from childhood to adulthood is characterised by substantive biological, psychological, and social changes. A majority of these changes are captured under the umbrella concept of adolescence, a period in which young people undergo biological changes and fulfil key developmental tasks towards independence and self-reliance (Blakemore & Mills, 2014; Linders, 2017). Although legal designations of adulthood (e.g. 18 years of age or older) suggest that fulfilment of this developmental process depends on shared chronological markers, there is extensive interindividual variability in the timing, tempo, and extent to which young people experience developmental changes as they transition from childhood to adulthood. In this chapter, we position adolescence within the broader ambit of the developmental continuum by referring to individuals between 10 and 24 years of age as young people}
Compared to their counterparts in more developed parts of the world, young people in Eastern and Southern Africa (ESA) must navigate developmental milestones within environments that often pose significant short-and long-term mental and physical health risks. Understanding developmental changes that accompany the transition to adulthood is key to identifying the challenges that young people experience within the broader sociocultural context in which they live. This chapter provides an overview of theoretical positions that are central to holistically understanding the biopsychosocial development of young people. It also offers a backdrop to subsequent chapters in this book, which focus on delineating mechanisms or processes that may deter health risk behaviours and promote well-being among young people. Drawing on theoretical perspectives rooted in biology, psychology, and

Figure 2.1 Conceptual framework for contextualised development of adolescents and young people
sociology, we outline fundamental processes that independently and conjunctively contribute to the contextualised development of young people (see Figure 2.1 for an overview of the interactive biopsychosocial systems involved in shaping the development of young people). Because HIV continues to have disproportionately devastating effects on young people living in ESA (see UNAIDS, 2017a, 2017b), understanding pathways of risk that have the potential to undermine the health and well-being of young people is integral to guiding the design and implementation of HIV prevention programming for this population.
A life-course perspective on the development of young people
Developmental psychology has traditionally dominated the way in which the experiences of young people have been constructed and understood (Burman, 2008). Traditional developmental discourse tends to assume that healthy and adaptive development is achieved through successful completion of developmental stages and attainment of age-related competencies (Burman, 2008; Hogan, 2005). This narrow perspective features several contentious assumptions, including framing development as a relatively homogenous and universal experience that is progressive, linear, and unidirectional. Emerging evidence suggests that developmental differences among young people are at least partly attributable to distinctions in both the inter- and intraindividual courses of progression, the sociocultural norms and expectations of adolescence, and the environmental context in which development occurs (Foulkes & Blakemore, 2018). Understanding qualitative (e.g. type) and quantitative (e.g. magnitude) differences in developmental experiences is critical to generating well-informed conceptualisations of development that are relevant to the contexts in which young people live.
A life-course perspective acknowledges developmental change in relation to social and structural determinants of health (Brook, Morojele, Zhang, 8c Brook, 2006; Sawyer et al., 2012). The development of young people unfolds as a transactional process that is the product of bidirectional and synergistic effects of the individual and their experiences within the social environment (Sameroff, 2009). Capacity for adaptive functioning is distributed across interacting systems and reflects evolutionary shifts in biology and culture, with maladaptive patterns representing decreases in functioning within and across multiple systems (Masten, 2014). Importantly, maladjustment can be attributed to or exacerbated by factors at cultural and contextual levels (i.e. social-structural vulnerabilities) that extend beyond the individual (Ungar, 2011). Social-structural vulnerabilities (e.g. lack of education, poverty, gender inequality, discriminatory policies or legal frameworks) tend to heighten exposure of young people to dysfunctional systems, which can disrupt typical trajectories of development and create barriers to successfully navigating pathways of risk. While risky behaviours are a part of the normative dialogue around the development of young people, environments that lack protective processes at social and structural levels may predispose this population to a variety of health risks (e.g. substance abuse, violence), including HIV. In the sections that follow, we consider salient development and role transition processes of young people and contextualise these in relation to some of the social-structural vulnerabilities that exist in ESA.