"It wasn't me, it was them!" social influence in risky behavior by adolescents

Peer effects in weight-related behaviours of young people: A systematic literature review

Individual preferences and beliefs are perpetually shaped by environmental influences, with peers playing a key role in this dynamic process. Compelling evidence from qualitative and quantitative studies has highlighted the significant impact of peer influence on health-related decisions. This systematic literature review critically synthesises findings from 45 studies published between 2011 and 2022, providing a comprehensive understanding of the nature of peer effects on dietary, physical activity and sleep behaviours during youth. The majority of studies indicated that social norms drive directional changes in eating and physical activity. Yet, our analysis revealed a notable gap in exploring alternative mechanisms, including social comparison and social identity, despite their potential relevance. Studies, generally classified as moderate to high quality, predominantly relied on self-reported data, potentially affecting the validity and reliability of measures. Meta-regression analyses suggest a small, but significant association of sample size with the magnitude, sign and significance of the reported peer effects. Moreover, studies focusing on physical activity are more likely to report significant outcomes, whereas findings on peer influence on sleep-related studies tend to reveal less pronounced effects, compared to studies on dietary behaviours. Experimental designs do not appear to increase the likelihood of finding significant effects when compared to other study designs. In conclusion, this synthesis emphasises the need for further research into the underlying mechanisms on peer effects to better inform policy-makers in designing effective policies for improving weight-related behaviours in young people.

The effect of marijuana use in adolescence on college and graduate degree attainment

We estimate the long-term effect of using marijuana in adolescence on college and graduate degree attainment measured approximately 20 years later. We rely on the first two waves (1994-1996) and the fifth wave (2016-2018) of the National Longitudinal Study of Adolescent to Adult Health and estimate instrumental variables models that exploit the network structure at the second degree by using marijuana use status of friends of friends who are not themselves friends of the respondent in order to instrument for the respondent's marijuana use. Our models also include school and grade fixed effects. Marijuana use in adolescence leads to a large reduction in the likelihood of college and graduate degree attainment by the time respondents are aged 33-43 years old.

Is Peer Influence Gender and Age Specific? Findings From a Sample of Justice-Involved Individuals

Peer influence is generally understood to be one of the primary predictors of crime and delinquency. It is unclear, however, whether the mechanism that connects peer association, endorsement of deviant values, and delinquent behavior applies equally across different age and sex groups. This study examined age- and gender-specific susceptibility to delinquent and prosocial peer influence using a sample of justice-involved individuals. Based on multigroup structural equation modeling, the author found the nexus among peer association, endorsement of deviant values, and violent delinquency varied across gender and age groups. Among adult male respondents, delinquent peers strengthened deviant culture whereas prosocial peers inhibited that culture. Among juvenile respondents, deviant culture was not inhibited by relationships with prosocial peers. The results for adult females showed no significant influence by either delinquent or prosocial peers.

Consumo e exposição a bebidas alcoólicas entre adolescentes brasileiros

Objetivo: analisar os indicadores referentes ao consumo de álcool entre escolares brasileiros de 13 a 17 anos em 2015 e 2019. Método: estudo transversal com dados da Pesquisa Nacional de Saúde do Escolar (PeNSE), realizadas em 2015 e 2019. Foram analisados os indicadores referentes ao consumo de álcool estratificados por sexo, faixa etária e dependência administrativa, sendo estimadas as prevalências e os respectivos intervalos de 95% de confiança (IC95%). Resultados: observou-se estabilidade nas prevalências de experimentação de bebida alcoólica alguma vez na vida, 61,4% (IC95%: 59,3;63,6) em 2015 e 63,3% (IC95%: 62,6;64,0) em 2019; o uso de álcool nos últimos 30 dias também se mostrou estável 29,3% (IC95%: 27,6;31,2) 2015 e 28,1% (IC95%: 27,3;28,8) em 2019; experimentação de álcool com 13 anos ou menos aumentou de 30,6% (IC95%: 28,7;32,6) em 2015 para 34,6% (IC95%: 33,8;35,3) em 2019; sofrer embriaguez na vida passou de 27,2% (IC95%: 25,4;28,9) em 2015 para 47,0% (IC95%: 46.0;47.9) em 2019; ter problemas com amigos devido ao consumo de álcool  aumentou de 9,3% (IC95%: 8,4;10,2) em 2015, para 15,7% (IC95%: 15,1;16,2) em 2019. Amigos que consomem álcool reduziu de 49,2% (IC95% 47,1;51,3) para 43,9% (IC95%: 43,0;44,7). Conclusão: evidenciou-se a precocidade da exposição ao álcool e grande magnitude desse fenômeno, o que expõe grande parcela dos adolescentes brasileiros a uma elevada carga evitável de morbimortalidade decorrente do álcool.

Effects of Communicating Prevalence Information about Two Common Health Conditions

Obesity and diabetes are widespread health conditions with rising prevalence rates in the United States. News stories and health campaign messages frequently feature prevalence rates of obesity and diabetes, at times under the expectation that such messages will increase readers' disease awareness, health behaviors, and policy support. At the same time, American adults overestimate the prevalence of obesity and diabetes in the absence of prevalence information, raising important questions about the implications of communicating accurate prevalence information that may be lower than baseline estimates. The current study examines the effects of communicating information about the prevalence of obesity and diabetes, varying the format of this information (using qualitative terms, raw frequencies, or percentages). Results from two pre-registered, web-based randomized experiments suggest that only prevalence statistics in percentage formats shift readers' prevalence estimates, though in some percentage formats these estimates were lower than observed in a no-message control group. Prevalence estimates, in turn, were positively associated with perceived social causes of obesity/diabetes, intensions for healthy behaviors, and support for policy-level solutions. These findings offer guidance for health communication campaigns that seek to increase healthy behavior and support for policies to address health conditions.

Asymptotic Properties of Quasi-Maximum Likelihood Estimators for Heterogeneous Spatial Autoregressive Models

In this paper, we address a class of heterogeneous spatial autoregressive models with all n(n−1) spatial coefficients taking m distinct true values, where m is independent of the sample size n, and we establish asymptotic properties of the maximum likelihood estimator and the quasi-maximum likelihood estimator for all parameters in the class of models, extending Lee’s work (2004). The rates of convergence of those estimators depend on the features of values taken by elements of the spatial weights matrix in this model. Under the situations where, based on the values of the weights, each individual will not only influence a few neighbors but also be influenced by only a few neighbors, the estimator can enjoy an n-rate of convergence and be asymptotically normal. However, when each individual can influence many neighbors or can be influenced by many neighbors and their number does not exceed o(n), singularity of the information matrix may occur, and various components of the estimators may have different (usually lower than n) rates of convergence. An inconsistent estimator is provided if some important assumptions are violated. Finally, simulation studies demonstrate that the finite sample performances of maximum likelihood estimators are good.

Malleability of Alcohol Consumption: Evidence from Migrants

How malleable is alcohol consumption? Specifically, how much is alcohol consumption driven by the current environment versus individual characteristics? To answer this question, we analyze changes in alcohol purchases when consumers move from one state to another in the United States. We find that if a household moves to a state with a higher (lower) average alcohol purchases than the origin state, the household is likely to increase (decrease) its alcohol purchases right after the move. The current environment explains about two-thirds of the differences in alcohol purchases. The adjustment takes place both on the extensive and intensive margins.

Gene-by-peer-environment interaction effects on cigarette, alcohol, and marijuana use among US high school students of European Ancestry

Research has shown that adolescents' substance use behavior is determined not only by individual characteristics but also by peer environments, and an emerging literature in social genomics has also found that individual genotypes moderate peer effects on egos' substance use. However, the previous literature on genetic by peer environment (GxPE) interaction effects is limited by the use of genetic measures with limited power and a lack of focus on causality. Based on a sample of about 4000 adolescents of European Ancestry from the National Longitudinal Study of Adolescent to Adult Health, this study utilizes polygenic scores to examine GxPE interactions between ego's genetics and peers' cigarette, alcohol, and marijuana use. The results show peers' cigarette and marijuana use positively affect ego's substance use, and peer effects are stronger when the ego is genetically predisposed to substance use. However, genetic propensities toward risk tolerance are found to weaken the peer effects on the ego's marijuana use. Overall, our findings provide new evidence for the existence of GxPE effects on adolescent substance use and reveal the multidimensional nature of GxPE effects.

The long-term health effects of initiating smoking in adolescence: Evidence from a national longitudinal survey

We estimate the long-term effect of initiating smoking in adolescence on a range of health outcomes later in life. We use the second wave (1996) and the fifth wave (2016-2018) of the National Longitudinal Study of Adolescent to Adult Health (Add Health) and estimate instrumental variables models with school-level fixed effects, where the instruments are the average rate of smoking among friends and the respondents' perceptions about their friends' smoking. We find that smoking in adolescence has a negative impact on 15 of the 28 self-reported, diagnosed, and self-identified health outcomes approximately 20 years later.

Proximity can induce diverse friendships: A large randomized classroom experiment

Can outside interventions foster socio-culturally diverse friendships? We executed a large field experiment that randomized the seating charts of 182 3^rd through 8^th grade classrooms (N = 2,966 students) for the duration of one semester. We found that being seated next to each other increased the probability of a mutual friendship from 15% to 22% on average. Furthermore, induced proximity increased the latent propensity toward friendship equally for all students, regardless of students’ dyadic similarity with respect to educational achievement, gender, and ethnicity. However, the probability of a manifest friendship increased more among similar than among dissimilar students—a pattern mainly driven by gender. Our findings demonstrate that a scalable light-touch intervention can affect face-to-face networks and foster diverse friendships in groups that already know each other, but they also highlight that transgressing boundaries, especially those defined by gender, remains an uphill battle.

Peer influence in adolescent drinking behavior: A meta-analysis of stochastic actor-based modeling studies

Objectives

To measure the effects of peer influence and peer selection on drinking behavior in adolescence through a rigorous statistical approach designed to unravel these interrelated processes.

Methods

We conducted systematic searches of electronic databases, thesis collections and conference proceedings to identify studies that used longitudinal network design and stochastic actor-oriented modeling to analyze drinking behavior in adolescents. Parameter estimates collected from individual studies were analyzed using multilevel random-effects models.

Results

We identified 26 articles eligible for meta-analysis. Meta-analyses for different specifications of the peer influence effect were conducted separately. The peer influence effect was positive for every specification: for average similarity (avSim) mean log odds ratio was 1.27 with 95% confidence interval [0.04; 2.49]; for total similarity (totSim) 0.46 (95% CI = [0.44; 0.48]), and for average alter (avAlt) 0.70 (95% CI = [-0.01; 1.41]). The peer selection effect (simX) was also positive: 0.46 (95% CI = [0.28; 0.63]). Conversion log odds ratio values to Cohen’s d gives estimates from 0.25 to 0.70, which is considered as medium to large effect.

Conclusions

Advances in methodology for social network analysis have made it possible to accurately estimate peer influence effects free from peer selection effects. More research is necessary to clarify the roles of age, gender, and individual susceptibility on the changing behavior of adolescents under the influence of their peers. Understanding the effects of peer influence should inform practitioners and policy makers to design and deliver more effective prevention programs.

Identifying sensitive periods when changes in parenting and peer factors are associated with changes in adolescent alcohol and marijuana use

PURPOSE

There are well-established associations between parental/peer relationships and adolescent substance use, but few longitudinal studies have examined whether adolescents change their substance use in response to changes in their parents' behavior or peer networks. We employ a within-person change approach to address two key questions: Are changes in parenting and peer factors associated with changes in adolescent marijuana and alcohol use? Are there sensitive periods when changes in parenting and peer factors are more strongly associated with changes in adolescent marijuana and alcohol use?

METHODS

We analyzed longitudinal data collected annually on 503 boys, ages 13-19, recruited from Pittsburgh public schools. Questionnaires regarding parental supervision, negative parenting practices, parental stress, physical punishment, peer delinquency, and peer drug use were administered to adolescents and their caretakers. Alcohol and marijuana use were assessed by a substance use scale adapted from the National Youth Survey.

RESULTS

Reductions in parental supervision and increases in peer drug use and peer delinquency were associated with increases in marijuana frequency, alcohol frequency, and alcohol quantity. Increases in parental stress were associated with increases in marijuana and alcohol frequency. The magnitudes of these relationships were strongest at ages 14-15 and systematically decreased across adolescence. These associations were not due to unmeasured stable confounders or measured time-varying confounders.

CONCLUSIONS

Reducing or mitigating changes in parenting and peer risk factors in early adolescence may be particularly important for preventing substance use problems as adolescents transition into young adulthood.

Misperceptions of the Prevalence of Health Conditions and Behaviors

Misperceptions about health conditions and behaviors may play a role in shaping health behaviors. Health messages frequently cite prevalence information in an effort to raise people's awareness of various health issues under the assumption that correcting misperceptions will increase healthy behavior. However, there is much to learn about the accuracy of estimates of the prevalence of prominent health conditions and behaviors among United States adults. We examined prevalence perceptions regarding a wide range of health conditions (obesity, diabetes, HIV infections, and HPV infections), health-risk behaviors (cigarette/e-cigarette use and binge drinking), and health-promotion behaviors (vegetable/fruit consumption, physical exercises, vaccination, and cancer screening) with a sample of U.S. adults stratified by race. We also examined perceptions of racial health disparities between white and black Americans. Respondents systematically overestimated the prevalence of health conditions and health-risk behaviors but underestimated the prevalence of health-promotion behaviors. Perceptions of racial disparities were comparable between white and black respondents. We end with a discussion of various implications related to misperceptions of prevalence estimates.

Smoking behavior prevalence in one's personal social network and peer's popularity: A population-based study of middle-aged adults in Japan

Although previous social network studies have consistently shown the social influence of peers' smoking on one's (ego's) smoking, few studies have examined how the influence differs according to peers' structural positions in the network. Investigations are also lacking on whether vulnerability to the influence varies by ego's socioeconomic position. Thus, the present study aimed to examine how the association between peers' smoking and ego's smoking differs by peers' popularity in ego's personal network and ego's educational attainment. We used data from the third-wave Japanese Study on Stratification, Health, Income, and Neighborhood (J-SHINE) conducted in 2017, which targeted middle-aged (32-58-year-old) residents in four municipalities within Japanese metropolitan areas. Information on four close peers' characteristics and behaviors and their mutual relationships was collected by the name generator and name interpreter methods. Data on 1989 respondents and 7956 peers were evaluated. Peers' eigenvector centrality was used as their popularity index in ego's personal network. We set ego's smoking as an outcome, regressed on each peer's smoking, each peer's popularity, and ego's educational attainment adjusting for ego's age, sex, working status, marital status, spouse's/partner's smoking status, as well as similarity in socioeconomic backgrounds between peer and ego, using a logistic regression model with robust standard errors. We then added a three-way interaction term for these three explanatory variables to the model. Results showed that peer's smoking status was related to ego's smoking even more strongly when the peer was popular but only in the case of ego with lower educational attainment. The results suggested that the disparity in smoking behavior across socioeconomic positions may be partly explained by susceptibility to social influence from one's personal network among the socioeconomically vulnerable. This study proposes a plausible method for pinpointing the peer influencer in one's personal social network to close the socioeconomic gap in smoking.

Religious Social Support Protects against Social Risks for Adolescent Substance Use

We used a social developmental perspective to identify how prominent social contexts influence substance use during adolescence. Longitudinal data were collected annually from 167 parent-adolescent dyads over four years. We investigated whether parent substance use was related to adolescent substance use directly and indirectly via peer substance use and whether these associations were moderated by religious social support. Structural equation modeling (SEM) analysis indicated significant moderated mediation: Greater parent substance use predicted increases in adolescent substance use indirectly via increased peer substance use when adolescent religious social support was low or average, but not high. These results suggest religious social support may protect adolescents against prominent social risks for intergenerational substance use.

Boundary violations and adolescent drinking: Observational evidence that symbolic boundaries moderate social influence

Scholars of social influence can benefit from attending to symbolic boundaries. A common and influential way to understand symbolic boundaries is as widely shared understandings of what types of behaviors, tastes, and opinions are appropriate for different kinds of people. Scholars following this understanding have mostly focused on how people judge others and how symbolic boundaries align with and thus reproduce social differences. Although this work has been impressive, I argue that it might miss important ways in which symbolic boundaries become effective in everyday social life. I therefore develop an understanding of how symbolic boundaries affect people's ideas and decisions about themselves and their own behavior. Based on this, I argue that focusing on boundary violations-that is, what happens if people express opinions or enact behavior that contravenes what is considered (in)appropriate for people like them-might offer an important way to understand how symbolic boundaries initiate and shape cultural and social change. Using data from Add Health, I demonstrate the utility of this line of argument and show that boundary violations play an important role in channeling social influence. Conservative/Evangelical Protestants and to a lesser degree Catholics, but not Mainline Protestants are highly influenced by the drinking of co-religionists. I consider the implications for cultural sociology.

Social Influence in Adolescent Decision-Making: A Formal Framework

Adolescence is a period of life during which peers play a pivotal role in decision-making. The narrative of social influence during adolescence often revolves around risky and maladaptive decisions, like driving under the influence, and using illegal substances (Steinberg, 2005). However, research has also shown that social influence can lead to increased prosocial behaviors (Van Hoorn et al., 2017) and a reduction in risk-taking (Braams et al., 2019). While many studies support the notion that adolescents are more sensitive to peer influence than children or adults, the developmental processes that underlie this sensitivity remain poorly understood. We argue that one important reason for this lack of understanding is the absence of precisely formulated models. To make a first step toward formal models of social influence during adolescence, we first identify three prominent verbal models of social influence in the literature: (1) social motivation, (2) reward sensitivity, and (3) distraction. We then illustrate how these can be translated into formal models, and how such formal models can inform experimental design and help identify developmental processes. Finally, by applying our formal models to existing datasets, we demonstrate the usefulness of formalization by synthesizing different studies with seemingly disparate results. We conclude with a discussion on how formal modeling can be utilized to better investigate the development of peer influence in adolescence.

Roommate effects in health outcomes

We use randomized roommate assignment in dormitories in a college in Kolkata in India to examine peer effects in weight gains among roommates. We use administrative data on weight, height, and test scores of students at the time of college admission and then survey these students at the end of their first and second years in college. We do not find any significant roommate specific peer effect in weight gain. Our results rather suggest that an obese roommate reduces the probability that the other roommates become obese in subsequent years. We examine potential mechanism using survey data on students' eating habits, smoking, exercise, and sleeping patterns. We find that obese roommates sleep longer, which in turn improves the sleep pattern of others, which might explain the weak negative effect of obese roommates on the weight of others in the same room.

Peer effects of obesity on child body composition

This study investigates whether peer obesity is a driver of individual weight changes in public school children and whether the impact of peer effects changes as children age. Quantifying peer effects is important for understanding the social determinants of obesity and for planning effective school wellness policies. However, the extant empirical research on peer effects is limited due to difficulties in separating causal influences from confounding factors. This study overcomes some of these difficulties by using a within-school, across-cohort empirical design to separate confounding factors at the individual, school and school-grade level for over one million public school children. The results show that increases a one standard deviation increase in average classmate body mass index (BMI) leads to a modest but meaningful increase of 0.395 standard deviation increase in a child's own BMI. Peer-effects are highest (0.813) for children in Kindergarten and decline with age. These findings suggest that the critical time for school-grade level intervention may be in the earliest ages of childhood development.

Peer influence in adolescent drinking behaviour: a protocol for systematic review and meta-analysis of stochastic actor-based modeling studies

INTRODUCTION

Alcohol consumption is a considerable public health problem that is especially harmful to young people. To develop effective prevention programmes targeted at adolescents, it is important to understand the social mechanisms triggering alcohol consumption. Among such mechanisms, peer influence plays an important role. The effects of peer influence are very difficult to evaluate because of the entanglement with social selection, that is, a tendency of people to befriend others with similar behaviour. The recently developed stochastic actor-oriented models (SAOM) approach is designed to disentangle social influence from social selection. The aim of this study is to conduct a systematic review and meta-analysis of studies employing SAOM methodology to evaluate the effects of social influence on adolescent drinking behaviour.

METHODS AND ANALYSIS

In order to analyse the co-evolution of alcohol consumption and adolescent friendship networks, we will collect articles that use SAOM methodology through systematic electronic searches in Web of Science, Scopus, PubMed, The Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials), EBSCOhost (MEDLINE, SocINDEX, Academic Source, ERIC), ProQuest (ProQuest Dissertations and Theses Global), PsycINFO (PsycNET), Excerpta Medica database (Embase) and Cumulative Index to Nursing and Allied Health Literature (CINAHL). We will collect the literature from academic journals, dissertations/theses, reports and conference materials. Three reviewers will retrieve and independently assess potentially relevant material in terms of whether they comply with prespecified criteria. Subsequently, we will summarise the results of the studies in a systematic review. If a sufficient number of studies can be found, SAOM quantitative results will be extracted and meta-analysed. The project will go from 1 December 2018 to 1 December 2019.

ETHICS AND DISSEMINATION

Ethical approval will not be required as our work is based on published studies. A list of all the studies included in this work will be available for review. We plan dissemination in a peer-reviewed international scientific journal and through conference presentations. Our review will highlight the peer effect of peers in adolescent drinking behaviour and provide guidance for developing effective prevention and intervention programmes. We expect it to be informative for policy and practice, decision-making as well as for further research in public health and sociology of adolescents.

PROSPERO REGISTRATION NUMBER

CRD42019119836.

The influence of misperceptions about social norms on substance use among school-aged adolescents

Individuals often have biased perceptions about their peers' behavior. We use an economic equilibrium analysis to study the role social norms play in substance use decisions. Using a nationally representative dataset, we estimate the effect of misperception about friends' alcohol, smoking, and marijuana use on consumption of these substances by youths in grades 7-12. Overestimation of friend's substance use significantly increases adolescent's own use approximately 1 year later, and the estimated effect is robust across specifications including individual-level fixed effects regression. The effect size is bigger for boys than for girls. The estimates for those who initially underestimated the norm suggest the possibility of a rebound/boomerang effect.

Environmental tobacco smoke exposure among electronic cigarette users

INTRODUCTION

Exposure to environmental tobacco smoke (ETS) from combustible tobacco products causes various diseases and makes quitting smoking more difficult. However, little is known about exposure of e-cigarette users to ETS from combustible tobacco products. This study aimed to investigate e-cigarette users' exposure to ETS from tobacco smokers.

METHODS

The association between ETS exposure frequency and different types of smokers including e-cigarette users was examined using ordered logistic regression analysis and nationally representative survey data on 28,765 individuals who were interviewed in the Canadian Tobacco, Alcohol and Drugs Surveys conducted during 2013 and 2015. Survey respondents were classified into one of five smoker types: smokers of tobacco only, dual users of tobacco and e-cigarettes, users of e-cigarette only, former smokers and never smokers. The analyses were conducted using the entire sample and by age group.

RESULTS

Young to mid-age (15-54) dual users of both regular cigarettes and e-cigarettes have higher ETS exposure than even tobacco smokers. Young to mid-age single users of e-cigarettes are less exposed to ETS than tobacco smokers, but still have higher ETS than never smokers. At older age (55+), both dual and single e-cigarette users face similar risks of ETS exposure as tobacco smokers.

CONCLUSIONS

E-cigarette users are at high risk of ETS exposure. Policies that target the behaviour of e-cigarette users as well as the environments surrounding them to address their high ETS exposure risk would be beneficial.

Peer effects on adolescent smoking: Are popular teens more influential?

Previous research on adolescent cigarette adoption has focused on peer influence and the perceived status gain from smoking but has ignored the status effects on peer influence. We analyze adolescent peer effects on cigarette consumption while considering the popularity of peers. The analysis is based on a four wave panel survey representative of American high school students. We measure peers' popularity by their eigenvector centrality in high school social networks. Using lagged peers' behavior, school fixed effects, and instrumental variables to control for homophily and contextual confounds, we find that the probability of smoking the following year increases with the mean popularity of smokers, while the popularity of non-smokers has the opposite effect. These effects persist seven and fourteen years later (wave 3 and 4 of the data). In addition, the probability of smoking increases with the smoking propensity of the 20% most popular teens and decreases with the smoking propensity of the bottom 80%. The results indicate the importance of knowing not only the smoking propensity within a school but also the location of smokers within the social hierarchy.

Blowing up money? The earnings penalty of smoking in the 1970s and the 21st century

We analyze the earnings penalty of smoking among Swedish twins in two social contexts: the 1970s, when smoking was common and widely accepted and when there were relatively few tobacco laws aiming to reduce smoking; and the 2000s, when smoking had become more expensive, stigmatizing and less common, and when tobacco laws and regulations had intensified. The results show that the short-term earnings penalty of smoking was much higher in the 21st century than in the 1970s for men. For women, smokers had on average higher annual earnings compared to nonsmokers in the 1970s, but lower annual earnings in the 2000s. In the long run, there was an earnings gap for men between never-smokers and continuous smokers, whereas there was a pronounced earnings 'bonus' of smoking cessation for women. The results emphasize the importance of social context and the long-term horizon when evaluating the consequences of smoking for earnings.

Love Conquers all but Nicotine: Spousal Peer Effects on the Decision to Quit Smoking

If two partners smoke, their quit behavior may be related through correlation in unobserved individual characteristics and through common shocks. However, there may also be a causal effect whereby the quit behavior of one partner is affected by the quit decision of the other partner. If so, there is a spousal peer effect on the decision to quit smoking. We use data containing retrospective information of Dutch partnered individuals about their age of onset of smoking and their age of quitting smoking. We estimate mixed proportional hazard models of starting rates and quit rates of smoking in which we allow unobserved heterogeneity to be correlated across partners. Using a timing of events approach, we determine whether the quitting-to-smoke decision of one partner has a causal effect on the quitting-to-smoke decision of the other partner. We find no evidence of substantial spousal peer effects in the decision to quit smoking. Apparently, love conquers all but nicotine addiction. Copyright © 2017 John Wiley & Sons, Ltd.

Estimating sibling spillovers in health: Evidence on symptoms

This paper estimates the sibling spillover effect in health symptoms using a sample of US adolescents from the National Longitudinal Study of Adolescent Health dataset. The research design of this paper is to restrict the sample to sibling pairs who are separated between schools, where one enters high school and the other middle school. Because of school separation, sibling pairs face independent health shocks from own school peers. The identification strategy further exploits variations in individual health across symptoms to control for unobserved individual heterogeneity, which flexibly partials out family correlated effects. Estimation results show that the sibling spillover effect is large as a one-standard-deviation increase in one sibling's frequency of developing a stomach ache or a loss of appetite increases the other sibling's frequency of having the same symptom by about 55% of a standard deviation. Further investigation suggests that the effect is not due to spillovers in drinking alcohol or depression, but probably due to the spread of contagious illnesses like the stomach flu.

Paternal Incarceration and Adolescent Social Network Disadvantage

Previous research has suggested that adolescent peers influence behavior and provide social support during a critical developmental period, but few studies have addressed the antecedents of adolescent social networks. Research on the collateral consequences of incarceration has explored the implications of parental incarceration for children's behavioral problems, academic achievement, health, and housing stability, but not their social networks. Using network data from the National Longitudinal Study of Adolescent Health, I find that adolescents with recently incarcerated fathers are in socially marginal positions in their schools and befriend more-marginal peers than other adolescents: their friends are less advantaged, less academically successful, and more delinquent than other adolescents' friends. Differences in network outcomes are robust to a variety of specifications and are consistent across race and gender subgroups. This study advances the social networks literature by exploring how familial characteristics can shape adolescent social networks and contributes to the collateral consequences of incarceration literature by using network analysis to consider how mass incarceration may promote intergenerational social marginalization.

Environmental risks outweigh dopaminergic genetic risks for alcohol use and abuse from adolescence through early adulthood

BACKGROUND

Alcohol use is a primary public health concern, particularly among adolescents and young adults. Based on the rapidly growing field of gene-environment models, this study assessed the combined role of environmental and dopamine-related genetic correlates of early alcohol use and abuse.

METHODS

Multilevel growth models assessed trajectories of alcohol use and intoxication and ordered logistic regressions assessed alcohol use disorder among a sample of 12,437 youth from the nationally representative Add Health study who were followed from mid-adolescence through early adulthood.

RESULTS

Endogenous and exogenous stressful life events and social norms supportive of alcohol use from parents and peers were significant predictors of alcohol use, intoxication, and alcohol use disorder, with consistent patterns across males and females. In contrast, a dopamine-system genetic risk score (GRS) was not associated with alcohol use trajectories nor alcohol use disorder in early adulthood, although weak connections emerged between the GRS and growth trajectories of intoxication, indicating that higher GRS predicted more frequent episodes of intoxication during the transition to adulthood but not during adolescence or later 20s. No evidence of gene-environment interactions emerged.

CONCLUSIONS

Results extend a substantial body of prior research primarily assessing single genetic polymorphisms in the dopamine system, suggesting that dopaminergic GRSs may be associated with more problematic alcohol behaviors at some developmental periods, but further, that social norms and stressful life experiences are more consistent correlates of early and problematic alcohol use among youth. These environmental factors present potential targets for research manipulating contexts to identify causal pathways.

The Influence of Classmates on Adolescent Criminal Activities in the United States

This article examines the effect of delinquent peers on an individual's criminal activity by leveraging quasi-experimental variation in exposure to peers, separating confounding and causal effects. In particular, we examine the role of wider peer networks (i.e., classmates) as a critical source of influence on adolescents' delinquent behavior. Using a combined instrumental variables/fixed effects methodology, we address important methodological challenges in estimating peer effects. Results suggest that increasing the proportion of peers who engage in criminal activities by 5 percent will increase the likelihood an individual engages in criminal activities by 3 percentage points.

Never-Smoking Adolescents' Exposure to Secondhand Smoke in Africa

INTRODUCTION

Though Africa is in Stage 1 of the tobacco epidemic, lack of effective public smoking laws or political will implies that secondhand smoke (SHS) exposure may be high in youth. The study objective is to estimate prevalence and identify determinants of SHS exposure among never-smoker adolescents in Africa and make cross-country comparisons.

METHODS

Pooled data from the Global Youth Tobacco Surveys conducted in 25 African countries during 2006-2011 were used. Based on the venue of exposure in past 7 days, SHS was categorized into exposure inside, outside, and overall exposure (either inside or outside of the home), respectively. Data were analyzed in 2015 using logistic regression models to identify factors related to SHS exposure in three venues.

RESULTS

About 21% and 39% of adolescents were exposed to SHS inside or outside of the home, with overall exposure of 45%. In all 25 African countries, parental smoking was significantly associated with SHS exposure inside the home (ORs ranging from 3.02 [95% CI=2.0, 4.5] to 14.65 [95% CI=10.0, 21.5]). Peer smoking was associated with SHS exposure outside the home in 18 countries (ORs ranging from 1.45 [95% CI=1.0, 2.1] to 3.00 [95% CI=1.8, 5.1]). Parental smoking, peer smoking, and anti-smoking messages in media were identified as three major factors associated with SHS exposure.

CONCLUSIONS

A significant proportion of never-smoking adolescents in Africa are exposed to SHS, suggesting the need for countries to adopt policies to protect never smokers through the implementation of the WHO Framework Convention on Tobacco Control.

Do Your School Mates Influence How Long You Game? Evidence from the U.S

The goal of this paper is to estimate peer influence in video gaming time among adolescents. Using a nationally representative sample of the U.S. school-aged adolescents in 2009–2010, we estimate a structural model that accounts for the potential biases in the estimate of the peer effect. Our peer group is exogenously assigned and includes one year older adolescents in the same school grade as the respondent. The peer measure is based on peers’ own reports of video gaming time. We find that an additional one hour of playing video games per week by older grade-mates results in .47 hours increase in video gaming time by male responders. We do not find significant peer effect among female responders. Effective policies aimed at influencing the time that adolescents spend video gaming should take these findings into account.

Cross-section and panel estimates of peer effects in early adolescent cannabis use: With a little help from my 'friends once removed'

Peer effects in adolescent cannabis are difficult to estimate, due in part to the lack of appropriate data on behaviour and social ties. This paper exploits survey data that have many desirable properties and have not previously been used for this purpose. The data set, collected from teenagers in three annual waves from 2002 to 2004 contains longitudinal information about friendship networks within schools (N = 5020). We exploit these data on network structure to estimate peer effects on adolescents from their nominated friends within school using two alternative approaches to identification. First, we present a cross-sectional instrumental variable (IV) estimate of peer effects that exploits network structure at the second degree, i.e. using information on friends of friends who are not themselves ego's friends to instrument for the cannabis use of friends. Second, we present an individual fixed effects estimate of peer effects using the full longitudinal structure of the data. Both innovations allow a greater degree of control for correlated effects than is commonly the case in the substance-use peer effects literature, improving our chances of obtaining estimates of peer effects than can be plausibly interpreted as causal. Both estimates suggest positive peer effects of non-trivial magnitude, although the IV estimate is imprecise. Furthermore, when we specify identical models with behaviour and characteristics of randomly selected school peers in place of friends', we find effectively zero effect from these 'placebo' peers, lending credence to our main estimates. We conclude that cross-sectional data can be used to estimate plausible positive peer effects on cannabis use where network structure information is available and appropriately exploited.

Perceived size of friends and weight evaluation among low-income adolescents

Drawing from social comparison theory, we examine how perceptions of friends' body sizes may influence adolescents' subjective evaluations of their own body (e.g., how accurate they are in judging their weight, how much body dissatisfaction they feel), particularly for adolescent females. Participants were low-income, minority adolescents (Study 1: N = 194 females, Mean age = 15.4; Study 2: N = 409 males and females; Mean age = 14.9). Adolescents used figure rating scales to indicate their perceived size and that of four of their closest friends and completed several measures of subjective weight evaluation (e.g., weight classification, body dissatisfaction, internalized weight bias). In both studies, how adolescents perceived their body size and the body sizes of their thinnest and heaviest friends were positively correlated. In Study 1, overweight females based on measured BMI were less likely to accurately judge themselves as overweight if they had a close friend they perceived as heavy. In addition, females who viewed themselves as having a larger figure reported more internalized weight bias when they had friends they viewed as relatively thin. Findings from Study 2 suggest that how friends' bodies are perceived is predictive of subjective weight evaluation measures only for adolescent females. Programs that address negative aspects of social comparison may be important in preventing both obesity and eating disorder symptoms in adolescent females.

Peer effects on risk behaviour: the importance of group identity

This paper investigates whether and to what extent group identity plays a role in peer effects on risk behaviour. We run a laboratory experiment in which different levels of group identity are induced through different matching protocols (random or based on individual painting preferences) and the possibility to interact with group members via an online chat in a group task. Risk behaviour is measured by using the Bomb Risk Elicitation Task and peer influence is introduced by giving subjects feedback regarding group members' previous decisions. We find that subjects are affected by their peers when taking decisions and that group identity influences the magnitude of peer effects: painting preferences matching significantly reduces the heterogeneity in risk behaviour compared with random matching. On the other hand, introducing a group task has no significant effect on behaviour, possibly because interaction does not always contribute to enhancing group identity. Finally, relative riskiness within the group matters and individuals whose peers are riskier than they are take on average riskier decisions, even when controlling for regression to the mean.

Escalating risk and the moderating effect of resistance to peer influence on the P200 and feedback-related negativity

Young people frequently socialize together in contexts that encourage risky decision making, pointing to a need for research into how susceptibility to peer influence is related to individual differences in the neural processing of decisions during sequentially escalating risk. We applied a novel analytic approach to analyze EEG activity from college-going students while they completed the Balloon Analogue Risk Task (BART), a well-established risk-taking propensity assessment. By modeling outcome-processing-related changes in the P200 and feedback-related negativity (FRN) sequentially within each BART trial as a function of pump order as an index of increasing risk, our results suggest that analyzing the BART in a progressive fashion may provide valuable new insights into the temporal neurophysiological dynamics of risk taking. Our results showed that a P200, localized to the left caudate nucleus, and an FRN, localized to the left dACC, were positively correlated with the level of risk taking and reward. Furthermore, consistent with our hypotheses, the rate of change in the FRN was higher among college students with greater self-reported resistance to peer influence.

Befriending Risky Peers: Factors Driving Adolescents' Selection of Friends with Similar Marijuana Use

Adolescents often befriend peers who are similar to themselves on a range of demographic, behavioral, and social characteristics, including substance use. Similarities in lifetime history of marijuana use have even been found to predict adolescent friendships, and we examine whether this finding is explained by youth's selection of friends who are similar on a range of more proximate, observable characteristics that are risk factors for marijuana use. Using two waves of individual and social network data from two high schools that participated in Add Health (N = 1,612; 52.7% male), we apply longitudinal models for social networks to test whether or not several observable risky attributes (psychological, behavioral, and social) predict adolescent friendship choices, and if these preferences explain friend's similarities on lifetime marijuana use. Findings show that similarities on several risk factors predict friendship choices, however controlling for this, the preference to befriend peers with a similar history of marijuana use largely persists. The results highlight the range of social selection processes that lead to similarities in marijuana use among friends and larger peer groups, and that also give rise to friendship groups whose members share similar risk factors for substance use. Friends with high "collective risk" are likely to be important targets for preventing the onset and social diffusion of substance use in adolescents.

Social interactions and college enrollment: A combined school fixed effects/instrumental variables approach

This paper provides some of the first evidence of peer effects in college enrollment decisions. There are several empirical challenges in assessing the influences of peers in this context, including the endogeneity of high school, shared group-level unobservables, and identifying policy-relevant parameters of social interactions models. This paper addresses these issues by using an instrumental variables/fixed effects approach that compares students in the same school but different grade-levels who are thus exposed to different sets of classmates. In particular, plausibly exogenous variation in peers' parents' college expectations are used as an instrument for peers' college choices. Preferred specifications indicate that increasing a student's exposure to college-going peers by ten percentage points is predicted to raise the student's probability of enrolling in college by 4 percentage points. This effect is roughly half the magnitude of growing up in a household with married parents (vs. an unmarried household).

US adolescents' friendship networks and health risk behaviors: a systematic review of studies using social network analysis and Add Health data

Background. Documented trends in health-related risk behaviors among US adolescents have remained high over time. Studies indicate relationships among mutual friends are a major influence on adolescents' risky behaviors. Social Network Analysis (SNA) can help understand friendship ties affecting individual adolescents' engagement in these behaviors. Moreover, a systematic literature review can synthesize findings from a range of studies using SNA, as well as assess these studies' methodological quality. Review findings also can help health educators and promoters develop more effective programs. Objective. This review systematically examined studies of the influence of friendship networks on adolescents' risk behaviors, which utilized SNA and the Add Health data (a nationally representative sample). Methods. We employed the Matrix Method to synthesize and evaluate 15 published studies that met our inclusion and exclusion criteria, retrieved from the Add Health website and 3 major databases (Medline, Eric, and PsycINFO). Moreover, we assigned each study a methodological quality score (MQS). Results. In all studies, friendship networks among adolescents promoted their risky behaviors, including drinking alcohol, smoking, sexual intercourse, and marijuana use. The average MQS was 4.6, an indicator of methodological rigor (scale: 1-9). Conclusion. Better understanding of risky behaviors influenced by friends can be useful for health educators and promoters, as programs targeting friendships might be more effective. Additionally, the overall MQ of these reviewed studies was good, as average scores fell above the scale's mid-point.

Separating boys and girls and increasing weight? Assessing the impacts of single-sex schools through random assignment in Seoul

A growing body of research reports associations of school contexts with adolescents' weight and weight-related behaviors. One interesting, but under-researched, dimension of school context that potentially matters for adolescents' weight is the gender composition. If boys and girls are separated into single-sex schools, they might be less concerned about physical appearance, which may result in increased weight. Utilizing a unique setting in Seoul, Korea where students are randomly assigned to single-sex and coeducational schools within school districts, we estimate causal effects of single-sex schools on weight and weight-related behaviors. Our results show that students attending single-sex schools are more likely to be overweight, and that the effects are more pronounced for girls. We also find that girls in single-sex schools are less likely to engage in strenuous activities than their coeducational counterparts.

Daily tobacco smoking, heavy alcohol use, and hashish use among adolescents in southern Sweden: A population-based multilevel study

Introduction

The aim of this study was to investigate school contextual effects on daily tobacco smoking, heavy alcohol use and hashish use among adolescents, using multilevel analyses adjusting for individual-level factors.

Methods

The 2012 public health survey among adolescents in Skåne includes pupils in ninth grade in primary school (predominantly 15–16 years old) and second grade in secondary school (gymnasium) (predominantly 17–18 years old). Multilevel logistic regressions were performed.

Results

The prevalence of all three behaviors was higher in the second grade in the gymnasium. Several sociodemographic, psychosocial and parental factors were associated with these behaviors. In the ninth grade, variance partition coefficients (VPCs) for tobacco smoking decreased from 10.2% in the empty model to 1.9% in the fully adjusted model, for heavy alcohol use from 6.5% to 6.3%, while VPCs for hashish increased from 9.9% to 11.0%. In the second grade, VPCs for daily tobacco smoking decreased from 13.6% in the empty model to 6.5% in the fully adjusted model, VPCs for heavy alcohol use decreased from 4.6% to 1.7%, and VPCs for hashish use increased from 7.3% to 8.3%.

Conclusions

Daily tobacco smoking (in both grades) and heavy alcohol use in the second grade in the gymnasium may be preventable by actions directed against individual-level protective factors including social capital, social support and peer/parent behavior and attitude, while interventions directed at school contexts may be more important for alcohol use in the ninth grade and hashish use in both grades.

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Smoking (both grades) and alcohol use (higher grade) depend on individual factors.

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Alcohol use (lower grade) and hashish use (both grades) depend more on school context.

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Trust is associated with all three behaviors, with the exception of hashish use in higher grade.

Predictors of condom use among peer social networks of men who have sex with men in Ghana, West Africa

Ghanaian men who have sex with men (MSM) have high rates of HIV infection. A first step in designing culturally relevant prevention interventions for MSM in Ghana is to understand the influence that peer social networks have on their attitudes and behaviors. We aimed to examine whether, in a sample of Ghanaian MSM, mean scores on psychosocial variables theorized to influence HIV/STI risk differed between peer social networks and to examine whether these variables were associated with condom use. We conducted a formative, cross-sectional survey with 22 peer social networks of MSM (n = 137) in Ghana. We assessed basic psychological-needs satisfaction, HIV/STI knowledge, sense of community, HIV and gender non-conformity stigmas, gender equitable norms, sexual behavior and condom use. Data were analyzed using analysis of variance, generalized estimating equations, and Wilcoxon two sample tests. All models were adjusted for age and income, ethnicity, education, housing and community of residence. Mean scores for all psychosocial variables differed significantly by social network. Men who reported experiencing more autonomy support by their healthcare providers had higher odds of condom use for anal (AOR = 3.29, p<0.01), oral (AOR = 5.06, p<0.01) and vaginal (AOR = 1.8, p<0.05) sex. Those with a stronger sense of community also had higher odds of condom use for anal sex (AOR = 1.26, p<0.001). Compared to networks with low prevalence of consistent condom users, networks with higher prevalence of consistent condom users had higher STD and HIV knowledge, had norms that were more supportive of gender equity, and experienced more autonomy support in their healthcare encounters. Healthcare providers and peer social networks can have an important influence on safer-sex behaviors in Ghanaian MSM. More research with Ghanaian MSM is needed that considers knowledge, attitudes, and norms of their social networks in the development and implementation of culturally relevant HIV/STI prevention intervention strategies.

Peer effects in risk aversion

We estimate peer effects in risk attitudes in a sample of high school students. Relative risk aversion is elicited from surveys administered at school. Identification of peer effects is based on parents not being able to choose the class within the school of their choice, and on the use of instrumental variables conditional on school-grade fixed effects. We find a significant and quantitatively large impact of peers' risk attitudes on a male individual's coefficient of risk aversion. Specifically, a one standard deviation increase in the group's coefficient of risk aversion increases an individual's risk aversion by 43%. Our findings shed light on the origin and stability of risk attitudes and, more generally, on the determinants of economic preferences.