We are the Association for Child and Adolescent Mental Health or ACAMH for short. And this is ACAMH Learn. Hi, there. So I'm Jack Andrews, and I'm a research fellow here at Oxford. And I study peer influences on adolescent mental health, and that's going to be the focus of this brief talk today. So adolescence, which can be defined as roughly the period of life between childhood and adulthood, or broadly the ages of 10 to 24, is a time of significant changes-- biological, psychological, and social. And in particular, it's a time of social reorientation, where adolescents are more likely to spend time with their peers compared to their parents, and when the thoughts, feelings, and behaviours of one's peers take on a step change and take on a particular salience during this period of life. What I'm going to try and do today is talk through how adolescence is a sensitive period for the emergence of mental health problems, and also how it's a sensitive period for peer influence effects. And then we're going to touch on selection and socialisation effects, components of peer influence. And then think about how interventions, particularly in school, might be able to harness peer influence effects in a positive way to improve behavioural and mental health outcomes for adolescents. So, as many of you know, probably adolescence is a period of life that is sensitive to the onset of many mental health problems. And I'm showing you some data here from Solmi et al, which shows age of onset on the x-axis and proportion of mental health instances on the y. And we can see here that the majority of mental health problems start in this period of life between the ages of about 10 and 24. And you can see this particularly so for things like eating disorders and mood disorders such as depression. There are a number of reasons why this might be the case, and we know that the peer environment is particularly important in influencing the onset of mental health problems. And what I'm going to show here is data from Sweden, large longitudinal data, in which young people aged 12 and 13 were asked, whom in this class do you best like to work with at school? And from this data, what the researchers were able to do was create a social network of individuals. And you can see here that each dot represents an individual and each line represents a friendship. So from this, they were able to identify who was very central in their peer network. So who was well liked and who was not well liked. And from this, they used this information to predict a number of outcomes later in life. And about 40 years later, what was found was that peer status, based on this single question in adolescence was predictive of things like suicide, mental, and behavioural disorders, and even heart disease later into adulthood. We also know that being bullied in adolescence is a particular risk factor for the onset of mental health problems. This is data coming from Lucy Bowes, also Oxford, and she found using the ALSPAC data, which is a cohort study in the UK, that different levels of bullying at age 13 were predictive of different degrees of depression at age 18. So what was found was that those individuals that reported frequent bullying at age 13 had a twofold increase in the risk of depression by the time they were 18. So we know that the peer environment is particularly salient and particularly important in the influence and development of mental health problems, both concurrently and also later into life. Peer influence itself refers to the way in which adolescents behaviours, attitudes, emotions, and beliefs are shaped by their peers. And this can occur through multiple processes, including social learning, imitation, and direct peer pressure. And we know that this is all influenced also by brain development and also by self-referential processing and feelings of things like embarrassment, which we know are particularly salient during adolescence as well. And peer pressure or peer influence-- sorry-- can be both direct. So direct peer pressure might be things like your friends telling you to engage in a risk taking behaviour or telling you not to be friends with another person. Or it can be indirect and very subtle. So just belonging to a peer group that is involved in certain behaviours or mindsets can subtly mean that you pick up those feelings and thoughts and behaviours. Much of the work, though, on peer influence, has historically been conducted on risky decision making. And what I'm going to first show you here is a quite famous, risky decision-making task by Larry Steinberg over in the United States. And the way this task works is that you, as the participant, in a simulated driving game, and the aim is to get to the end of the track as quickly as possible. And if you get to the end of the track, you get more money. What's interesting here, though, is that at each intersection, there is a traffic light, and you have a decision to make. If the traffic light is green, great. You can keep going. But if it's red, you have to decide if you are to stop and wait and obviously not get to the end of the track and not get as much money or jump the red light. But by jumping the red light, you risk potentially being crashed into by another car and losing your money. And multiple groups of individuals were brought in to do this, so adolescents, young adults, and adults. And they were asked to do this in two conditions. First, by playing it alone and then when being watched by two friends. What's interesting here is that adolescents and young adults and adults all had very similar number of crashes, or they took a similar number of risks when playing alone. However, when playing in the presence of their friends, we can see here that the younger adolescents had a threefold increase in the number of risks or red lights they jumped relative to adults. So it's the peer environment that is augmenting or changing the way in which young people take risks. We also know that risks that adolescents take or want to avoid are not just physical, they're also social. So a social risk might be a decision or an action that might lead to being rejected, or it might highlight that the adolescent is quite dissimilar from their friends, things that they might want to avoid. So many of these social risks that young people are faced with might be things like defending an unpopular opinion or arguing with a popular friend in a group of people. We know that adolescents are more concerned than adults about these social risks. And adolescents that are particularly concerned about engaging in these types of social risks also have a higher risk for depression compared to adults. One reason that they might be likely to avoid these types of social risks is because adolescence is also a period of heightened sensitivity to social rejection, and this is true both on and offline. And we know that adolescents, who report higher levels of social rejection sensitivity, are also more likely to report higher levels of depression compared to adults. And as you can see here from this graph on the right, rejection sensitivity decreases with age. So adolescents, shown further over on the left, have a higher rate of social rejection sensitivity compared to adults. And we also know that this is especially true for victimised adolescents. So adolescents that are victimised or bullied are more likely to be sensitive to social rejection, and therefore, also more likely to take certain risks that might increase their social status. So there are two core mechanisms of peer influence, that impact adolescent mental health that I want to touch upon. The first is social selection, which many people may have heard of as the idea of birds of a feather flock together or misery loves company, and this is the idea that adolescents might seek out similar others. So if you're feeling a bit down or anxious, you might also seek out friends that are also feeling down or might also be a bit anxious. And then these experiences increase together over time. Another process, though, is socialisation or social contagion. So this is the idea that adolescents pick up the negative mood or the negative behaviours, or positive mood or positive behaviours of their peers over time, through a process of by proxy of being friends with them. So one individual might start off happy and by being friends with somebody that's a bit sad, they may then get a bit sadder over time. And this is a contagion effect that we can model using network approaches or social network modelling. One study that recently showed this was a study published in JAMA Psychiatry. And what this study found was that by belonging to a class where more individuals were diagnosed with a mental health disorder, this increased the chance or the odds of other young people in that class later to go on to develop a mental health disorder. What's tricky about this study, though, is that they didn't collect network data, so it's hard to disentangle whether this is a socialisation or a selection effect. So it might just be that friends are more likely to select other friends that were depressed or had a diagnosis and then go and seek for a diagnosis. But it could also be a socialisation effect, whereby young people are then influenced by the fact that they're being in a class of others that have a mental health disorder. In order to fully disentangle this, though, we need to collect network data over time. And this is where individuals in a school class might report who they like and dislike, so we can work out who's friends with who and who isn't friends with who. And then this can be mapped in the way that I'm showing you here on the right. So each node is an individual, and each line is a friendship. Some studies have done this. And this is a very famous study, one of the first studies to do this, which was the Framingham Heart Study, which was initially a big study that was designed in Massachusetts, to map the social network of a whole town, particularly to look at risk of heart disease and how the risk of heart disease might spread. But what they also did was collected data on mental health symptoms. And what they were able to do was show that depressive symptoms did cluster in families and in social environments for all individuals in Framingham. And they also showed that the risk of an individual feeling low or depressed mood increased by the number of peers or people they interacted with that also felt depressed at a prior wave. So this is showing some indication of influence effects here. Importantly, there's also been data that's shown in adolescents in various contexts that mental health symptoms, particularly mood, can propagate through peer networks in a contagious sort of way. So this is data. The first study here is coming from a music camp. This is data collected by Stephanie Burnett Hayes, who showed that adolescents that were in a music camp, where their mood was monitored on a daily basis, were more likely to align their mood with individuals that they were interactive partners with, so who they were playing music with. So what they showed here was that mood spread among those individuals that they were spending a lot of time with. What's important here, as well, in this study was that they showed that negative mood was more likely to spread positive mood. Indeed, there's also other studies, such as studies from college roommates and in school classes, showing that negative mood and positive mood can spread through peer networks. There's also some experimental evidence that being exposed to peer's self-harm urges increases one's own urges to self-harm as well. So we know that it's not just specific to mood, it's also specific to behaviours that could be or also extends to behaviours that are related to mental health outcomes. One mechanism that might be underlying these socialisation effects is co-rumination. And this is where individuals engage in unhelpful conversations around their mood or mental health with their peers, and conversations that don't have a easy solution or they aren't solution focused, so where people might repetitively go over a negative event with a friend. And this can then also induce negative feelings in the co-rumination partner. And this may be one reason or one way in which it spreads. And there's some evidence that co-rumination is higher among girls than boys. And this may go in some way to explain why we see higher rates of mental health problems in girls than in boys. There's also evidence that mental health problems can be reinforced through deviancy training, so this is the idea that peers reinforce problematic behaviours through approval or seeing it as cool or popular. We know in from college roommate and dorm studies as well, that when you randomly pair people with problematic alcohol behaviours, they're also more likely to then pick up these negative and alcohol behaviours and drink a lot more than they would if they were randomly assigned to also being in a dorm with other individuals that didn't have problematic alcohol use. One reason this might be is that if we think that drinking alcohol is popular, people are more likely to do it. And if you're placed in a dorm where lots of people think it's a popular behaviour, you're going to reinforce that and that behaviour is going to be reinforced. So there are many ways in which peer influences can be harnessed or used to try and improve outcomes among young people. And there are several programmes that take this approach. For example, there's the ROOTS study, which is an anti-bullying intervention that was developed over in the United States by Betsy Levy Paluck. And there's also Sources of Strength, which is a suicide prevention study that tries to increase help-seeking behaviours among young people. One commonality among these interventions is that what they do is they try to use well-liked or popular peers to deliver the interventions themselves, obviously with some adult oversight. But the primary principle here is that it's the peers that are delivering the intervention themselves. And this is important because there is some evidence suggesting that actually adult-led interventions, particularly in the bullying space, are quite unhelpful and could potentially even be problematic when we get into that adolescent age group. So this gives ownership and autonomy to young people as well. Again, one primary example is this ROOTS study that was published in 2016. And what they did here was they got all young people in some school classes to rate who they liked and who they thought were good friends. And they found the most popular kids in the school or these well-liked children in the school, and they were termed the socially referent individuals. And it was these socially referent individuals that then delivered their own anti-bullying campaigns. And these were grassroots led. So they were able to do it in multiple different ways. They could devise their own social media campaign or run posters or wristbands or however they wanted to do it. So each intervention was slightly different and tailored to the school and delivered by the young people themselves. And then this was compared to control schools, which was just standard teacher-led bullying interventions. So what we can see here is that in those schools that had the peer-led approach, so where the peers were delivering the intervention, there was a reduction in victimisation by about 25% over the space of a year, which is a really huge decrease relative to the control schools that just had standard, usual school practise. Importantly here as well, the effect was stronger when the C group or the particular treatment school contained more of these socially referenced students who were well liked delivering these interventions. So what this shows here is that peer-led approaches have the capacity to improve behavioural outcomes that can have significant knock-on effects to mental health among young people. There's still many things we don't know about peer influences on adolescent mental health, so we don't yet know exactly who's susceptible to certain types of influence, so socialisation and selection. There's some evidence, potentially, that victimised young people might be more susceptible to socialisation effects, but these need to be tested and replicated. There's also contextual and cultural differences that we don't and whether or not these influences extend across different cultural groups and different school climates, which also need to be replicated and tested in large-scale studies. So in summary, what we've seen today is that the peer environment has a large impact on adolescent mental health outcomes. And we know that there's huge peer influences that can act on young people and in many different ways. And these can occur through both selection and influence effects or socialisation effects. But we can also use social influence or peer influence in positive ways to try and improve mental health and behavioural outcomes among young people, as we've seen in those anti-bullying interventions. [MUSIC PLAYING]