In this brief introduction, I will review the conceptual framework for adolescent health that we're using for the course, in order to focus the next set of lectures, which are going to be on risk and protective factors and the social determinants of health. This is the conceptual framework that we reviewed last week with the yellowy orange or horizontal axis here really referring to where adolescence sits within the life course, with an important, in a sense, biological understanding of adolescence. The vertical axis starting in blue and then heading down towards the green is what we highlighted as being the social determinants of health, or risk and protective factors. And we highlighted that adolescence is, if you like, sitting at that intersection between a life course or biological perspective on one hand, and social determinants of health on the other. Just as a reminder of language, we're referring to the social determinants of health as the conditions in which people are born, grow, live, work, and age. And we're referring to risk and protective factors here in this box, with risk factors predicting an increased likelihood of problems, and protective factors mediating or moderating exposure to risk, or directly decreasing the chance of problems. And then in green, we look at the intersection of biology and social determinants, and the influence of this on what we refer to as health-related behaviors and states. These are behaviors such as tobacco smoking, or unsafe sexual intercourse, or states such as mental disorder, or overweight and obesity, that positively or negatively affect health. I use that analogy of our onion, referring to the individual in the middle, surrounded by family, school, and peers, community, and national factors, which will both increase and reduce the likelihood of negative health outcomes. But there's a couple of points I'm just wanting to also get us to be thinking about. And I'm wanting us to refer to a different sort of theory of child development. And this is Urie Bronfenbrenner's Ecological Systems Theory. You can see these concentric circles just like we had developed in our previous model. And these refer to the individual in the middle, within, surrounded by fairly complex language. You could argue the microsystem, the mesosystem, the exosystem, macrosystem and chronosystem. Urie Bronfenbrenner was an American developmental psychologist, and he viewed the process of human development as being shaped by the interaction between an individual and their environment. With a specific path of development, a result of the many different levels of environmental influences that can affect a person such as their parents, their friends, school, work, community, and culture. Just like our previous onion model. The social determinants of health, in our conceptual framework, occur outside the individual. But the reason to put up Bronfenbrenner's model is for a couple of things. Firstly, in his original model, he didn't include biological processes that relate to the individual. You'll remember that last week, we spent a lot time covering the importance of biological development in childhood and adolescence, in terms of puberty and brain maturation. And it's interesting that Bronfenbrenner eventually renamed his theory the Bioecological Model, in order to, if you like, belatedly recognize the importance of biological processes in child development. He recognized biology as producing a person's potential. With this potential being realized or not by environmental, if you like, social forces. And like the onion analogy from last week, these concentric circles can be thought of as different environmental spheres of influence. Bronfenbrenner used this language of systems, as I said, micro, meso, macro systems to refer to the different types of influences. And specifically, one of the things that I like about his approach, is the level he refers to explicitly as the meso system. Which acknowledges the interactions between these different influences, and how one can influence the other. Just, if you like, as a parent who becomes unemployed, and perhaps becomes depressed as a result of that, will influence their child and adolescence experiences of growing up in that family. So we can see the interaction of these factors around the individual is important. But interestingly, just like Bronfenbrenner later added biology, he also later added the dimension of time. And he referred to this as the Chronosystem. So on this diagram, that's the circle right on the very outside, which at the bottom you just see describes the dimension of time. Now you'll remember when we go back to our conceptual framework for adolescence, it's intrinsically centered on the notion of time, if you like. On the central importance of adolescence within the life course, and the exquisite sensitivity of this biological phase, to how the social determinants that have particular significance during adolescence, such as economic factors, educational opportunities, gender norms, and sexuality, will then impact on adolescent health. So, let's return to our conceptual framework, and you'll see here that the focus is on the blue part, or that top part of our conceptual framework. Because in the next section, this is the part of the conceptual framework that we are going to be paying much more detailed attention to. Focusing firstly on those more proximal risk and protective factors that influence adolescent health, and then on the structural social determinants that influence health.