The ways that psychopathology manifests in adolescence have shifted dramatically over the past twenty-five years, with rates of many externalizing behaviors declining substantially while rates of anxiety and depressive disorders have skyrocketed. This paper argues that understanding these changes requires rethinking the field’s historically somewhat negative views of intense peer connections, peer influences, and adolescent risk-taking behavior. It is argued that intense peer connections are critical to development, and that peer influence and risk taking have important, often overlooked, adaptive components. The shift in observed manifestations of adolescent psychopathology over this period can be viewed at least partly in terms of a shift away from strong peer connections and toward greater risk aversion. Implications for research and intervention based on a focus on the adaptive aspects of peer influences and risk taking are discussed.

The current study investigated in-the-moment links between adolescents’ autonomic nervous system activity and susceptibility to three types of peer influence (indirect, direct, continuing) on two types of behavior (antisocial, prosocial). The sample included 144 racially ethnically diverse adolescents (46% male, 53% female, 1% other; Mage = 16.02 years). We assessed susceptibility to peer influence behaviorally using the Public Goods Game (PGG) while measuring adolescents’ mean heart rate (MHR) and pre-ejection period (PEP). Three key findings emerged from bivariate dual latent change score modeling: (1) adolescents whose MHR increased more as they transitioned from playing the PGG alone (pre-influence) to playing while simply observed by peers (indirect influence) displayed more prosocial behavior; (2) adolescents whose PEP activity increased more (greater PEP activity = shorter PEP latency) as they transitioned from indirect influence to being encouraged by peers to engage in antisocial behavior (direct influence) engaged in more antisocial behavior; and (3) adolescents whose PEP activity decreased less as they transitioned from direct influence on prosocial behavior to playing the PGG alone again (continuing influence) displayed more continuing prosocial behavior (marginal effect). The discussion focuses on the role of psychophysiology in understanding adolescents’ susceptibility to peer influence.

Smoking is a major cause of worldwide morbidity and mortality. Almost no evidence-based intervention programs are available to help youth quit smoking. We argue that ineffective targeting of peer influence and engagement difficulties are significant barriers to successful youth smoking cessation. To address these barriers, we developed the mobile game intervention HitnRun. A two-armed randomized controlled trial (RCT; n = 144) was conducted and young smokers (Mage = 19.39; SDage = 2.52) were randomly assigned to either play HitnRun or read a psychoeducational brochure. Prior to, directly following the intervention period, and after three-month follow-up, weekly smoking behavior, abstinence rates, intervention dose, and peer- and engagement-related factors were assessed. Results indicated similar reductions in weekly smoking levels and similar abstinence rates for both groups. Yet, we found a dose effect with HitnRun only: The longer participants played HitnRun, the lower their weekly smoking levels were. In the brochure group, a higher dose was related to higher weekly smoking levels at all measurement moments. Exploratory analyses showed the most powerful effects of HitnRun for participants who connected with and were engaged by the intervention. Future work should build on the promising potential of HitnRun by increasing personalization efforts and strengthening peer influence components.

Adolescent association with deviant and delinquent friends was examined for its roots in coercive parent–teen interactions and its links to functional difficulties extending beyond delinquent behavior and into adulthood. A community sample of 184 adolescents was followed from age 13 to age 27, with collateral data obtained from close friends, classmates, and parents. Even after accounting for adolescent levels of delinquent and deviant behavior, association with deviant friends was predicted by coercive parent–teen interactions and then linked to declining functioning with peers during adolescence and greater internalizing and externalizing symptoms and poorer overall adjustment in adulthood. Results are interpreted as suggesting that association with deviant friends may disrupt a core developmental task—establishing positive relationships with peers—with implications that extend well beyond deviancy-training effects.

We examined social mechanisms that account for similarity in the social context of school-sponsored extracurricular sports activities among friends. We distinguish two social mechanisms: “shared sports activities that lead to friendship,” whereby friendship formation and maintenance are conditioned by joint sports participation, and “friendship that leads to shared sports activities,” a form of social influence whereby adolescents join or maintain certain sports activities based on their friends' choices. Using a longitudinal sample of 1,776 10th graders at five high schools in Southern California, we employed a stochastic actor-oriented multivariate dynamic model to model the dynamic interplay between the two-mode affiliation network of adolescents' participation in sports activities and the one-mode friendship network. As a corresponding descriptive method, we propose a quantitative measure for the relative strength of the two-mentioned mechanisms as explanations of the association between the one-mode and the two-mode network. Further, we introduce two specifications that represent homophily effects in the two-mode network and apply them to test gender homophily in sports participation. The results provide strong evidence for both mechanisms, with friendship leading to shared sport activities as stronger than shared sports activities leading to friendships in explaining adolescents' friendships with co-participants.

Social networks, particularly those defined by friendships, influence many childhood and adolescent health behaviors such as the use of alcohol, tobacco, and other drugs, as well as diet and physical activity. Few, if any, studies have examined the concordance between friendship networks and sun exposure/safety behaviors. This study examines the friendship networks and sun safety behaviors for a group of fourth and fifth grade students taking part in a larger sun safety intervention, “SunSmart” (n = 128). Intra-class correlation, homophily hypothesis testing, and exponential random graph models were used to test friendship homophily based on sun safety behaviors. Peer Leaders were identified through social network popularity, and sun safety change scores were compared between Peer Leaders and non-leaders. Results show that students cluster based on shared demographic characteristics and some sun safety behaviors, and that there was a trend for Peer Leaders to respond better to the SunSmart intervention than non-leaders. Implications for future sun safety interventions using Peer Leaders as champions for sun safety behavior change are discussed.

This study addressed the role of influencer and influencee peer status in social influence of status-unrelated behaviours among emerging adults, while disentangling two forms of peer status, being liked (preference) and being powerful (popularity). Peer influence was examined in 67 women (M age = 20.5 years, SD = 2.1 years) using an experimental design. Popularity of the influencers and influencees (participants), as well as influencees’ preference and self-esteem were considered. Peer influence was measured through imitation of status-unrelated behaviours and task partner choice. In both tasks, influencees moved away from, rather than towards, a popular peer. Popular young women with low self-esteem were most likely to imitate a popular peer. Unpreferred young women with high self-esteem were least likely to imitate a popular peer. The findings demonstrate that the role of peer status in social influence processes is not limited to adolescence, and that the peer status of influencers and the influencees continues to affect social influence on status-unrelated behaviour in emerging adulthood.

In the present study, we examined the association between maternal education and unhealthy eating behaviour (the consumption of snack and sugar-sweetened beverages (SSB)) and explored environmental factors that might mediate this association in 11-year-old children. These environmental factors include home availability of snacks and SSB, parental rules about snack and SSB consumption, parental intake of snacks and SSB, peer sensitivity and children's snack-purchasing behaviour. Data were obtained from the fourth wave of the INPACT (IVO Nutrition and Physical Activity Child cohorT) study (2011), in which 1318 parent–child dyads completed a questionnaire. Data were analysed using multivariate regression models. Children of mothers with an intermediate educational level were found to consume more snacks than those of mothers with a high educational level (B= 1·22, P= 0·02). This association was not mediated by environmental factors. Children of mothers with a low educational level were found to consume more SSB than those of mothers with a high educational level (B= 0·63, P< 0·01). The association between maternal educational level and children's SSB consumption was found to be mediated by parental intake of snacks and SSB and home availability of SSB. The home environment seems to be a promising setting for interventions on reducing socio-economic inequalities in children's SSB consumption.

Both peer groups and genetics have been associated with adolescent smoking behavior. Recently, Loehlin (Loehlin, J. C. (2010). Is there an active gene–environment correlation in adolescent drinking behavior? Behavior Genetics, 40, 447–451) reported that twin differences in alcohol use were associated with differences in the number of common friends. Twins with more common friends were more similar in drinking, but only for dizygotic pairs. Using the same sample as Loehlin's (the National Merit twins), we replicated all of these findings for a composite cigarette smoking measure and for smoking initiation, but not persistence. The pattern of results is most consistent with homophily, or the tendency to associate with individuals that are like oneself. If peer influence occurs in the presence of homophily, then active genotype–environment correlation will be induced.

Self-identification with peer crowds (jocks, popular kids, druggies, etc.) has an important influence on adolescent substance use behavior. However, little is known about the impact of the shared nature of crowd identification on different stages of adolescent drinking behavior, or the way crowd identification interacts with participation in school-sponsored sports activities. This study examines drinking influences from (1) peers with shared crowd identities, and (2) peers who jointly participate in organized sports at their school (activity members). This study introduces a new network analytic approach that can disentangle the effects of crowd identification and sports participation on individual behavior. Using survey data from adolescents in five high schools in a predominantly Hispanic/Latino district (N = 1,707), this paper examines the association between social influences and each stage of drinking behavior (intention to drink, lifetime, past-month, and binge drinking) by conducting an ordinal regression analysis. The results show that both shared identities and joint participation were associated with all stages of drinking, controlling for friends' influence. Additionally, shared identification overlapped with joint participation was associated with more frequent drinking. Related policy implications are discussed.

We use data on a real, large-scale social network of 27 million individuals interacting daily, together with the day-by-day adoption of a new mobile service product, to inform, build, and analyze data-driven simulations of the effectiveness of seeding (network targeting) strategies under different social conditions. Three main results emerge from our simulations. First, failure to consider homophily creates significant overestimation of the effectiveness of seeding strategies, casting doubt on conclusions drawn by simulation studies that do not model homophily. Second, seeding is constrained by the small fraction of potential influencers that exist in the network. We find that seeding more than 0.2% of the population is wasteful because the gain from their adoption is lower than the gain from their natural adoption (without seeding). Third, seeding is more effective in the presence of greater social influence. Stronger peer influence creates a greater than additive effect when combined with seeding. Our findings call into question some conventional wisdom about these strategies and suggest that their overall effectiveness may be overestimated.

The present experimental study was the first to investigate the impact of a remote (non-existent) peer on children's food choice of familiar v. unfamiliar low- and high-energy-dense food products. In a computer task, children (n 316; 50·3 % boys; mean age 7·13 (sd 0·75) years) were asked to choose between pictures of familiar and unfamiliar foods in four different choice blocks using the following pairs: (1) familiar v. unfamiliar low-energy-dense foods (fruits and vegetables), (2) familiar v. unfamiliar high-energy-dense foods (high sugar, salt and/or fat content), (3) familiar low-energy-dense v. unfamiliar high-energy-dense foods and (4) unfamiliar low-energy-dense v. familiar high-energy-dense foods. Participants who were not in the control group were exposed to the food choices (either always the familiar or always the unfamiliar food product) of a same-sex and same-age fictitious peer who was supposedly completing the same task at another school. The present study provided insights into children's choices between (un)familiar low- and high-energy-dense foods in an everyday situation. The findings revealed that the use of fictitious peers increased children's willingness to try unfamiliar foods, although children tended to choose high-energy-dense foods over low-energy-dense foods. Intervention programmes that use peer influence to focus on improving children's choice of healthy foods should take into account children's strong aversion to unfamiliar low-energy-dense foods as well as their general preference for familiar and unfamiliar high-energy-dense foods.