Having the wrong friends? Peer effects in adolescent substance use

Gendered pathways to young adult symptomatology

The transition to adulthood is a critical juncture in the course of psychopathology. This study examined the ways in which earlier capacity to deal with relationship stress during adolescence contributed to an adaptive outcome in emerging adulthood. In a prospective study of 145 individuals, relationship stress, individual coping capacities, and perceived support from fathers, mothers, and peers were analyzed, when the participants were 13 and 17 years old. The effects of these earlier capacities to deal with relationship stress on health outcomes were examined in young adulthood (age 23). Gendered pathways to young adults’ symptomatology emerged. Females experiencing earlier relationship stress, but also support by mothers, fathers, and friends, showed less symptomatology at age 23. In addition, females’ withdrawal coping mediated the impact of stressful encounters on later internalizing symptomatology. In contrast, earlier coping with relationship stress was not found to be predictive for males. Earlier support from parents or friends was associated with later externalizing symptomatology in young men. Reasons for the gender-specific pathways to symptomatology are discussed.

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.

The effect of peers on HIV infection expectations among Malawian adolescents: Using an instrumental variables/school fixed effect approach

Malawian adolescents overestimate their HIV infection risk. Understanding why they do so is important since such overestimation is likely to be linked to later-life outcomes. This study focuses on the influence peers have on HIV infection expectations. I use novel school-based survey data collected in Malawi between October 2011 and March 2012 (n = 7910), which has more reliable measures of peers' HIV infection expectations than other studies. I employ a combined instrumental variables/fixed effects methodology designed to addresses several methodological challenges in estimating peer effects, including self-selection of friends, the issue of unobserved environmental confounders, and the bi-directionality of peer effects. Several tests are conducted in order to assess the robustness of the specifications. Results suggest that a one-percentage-point increase in the mean probabilistic expectation of HIV infection among peers increases an adolescent's own subjective expectation of infection by an average of 0.65 percentage points. This paper shows that peer influence is greater for males than for females. Results also suggest that the peer effects on HIV infection expectations are only statistically significant among those lacking more complete knowledge of HIV/AIDS.

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).

Review of hookah tobacco smoking among college students: policy implications and research recommendations

BACKGROUND

About 30% of college students have smoked hookah tobacco. Although most students perceive this product to be innocuous and non-addictive, hookah tobacco increases the risk for disease and nicotine dependence. Currently, the US Food and Drug Administration (FDA) does not regulate the manufacture, distribution, or sale of hookah tobacco.

OBJECTIVE

Empirical literature pertaining to hookah tobacco smoking is reviewed with a focus on the implications for regulatory policy.

METHODS

PubMed, PsycINFO, and Scopus databases were searched to locate articles published in English. The literature search combined several key words including "hookahs", "college", "advertising", "health effects", and "health policy".

RESULTS

Smoking hookah tobacco may play a role in the initiation of smoking among tobacco-naïve college students and may portend persistent smoking among those who have smoked cigarettes. College students are typically nondaily, social smokers. They do not perceive that their heightened risk for tobacco diseases and nicotine dependence relates to their smoking behavior. However, few public health messages target college-age adults to counter media messages that endorse hookah tobacco smoking.

CONCLUSION

Given that the FDA is not authorized to ban specific tobacco products, policy actions should focus on the development of effective risk communication strategies that target college-age adults and on limiting the accessibility of hookah tobacco products to these adults. Accordingly, a research agenda that would inform these policy actions is proposed.

Economic behavior under the influence of alcohol: an experiment on time preferences, risk-taking, and altruism

We report results from an incentivized laboratory experiment undertaken with the purpose of providing controlled evidence on the causal effects of alcohol consumption on risk-taking, time preferences and altruism. Our design disentangles the pharmacological effects of alcohol intoxication from those mediated by expectations, as we compare the behavior of three groups of subjects: those who participated in an experiment with no reference to alcohol, those who were exposed to the possibility of consuming alcohol but were given a placebo and those who effectively consumed alcohol. All subjects participated in a series of economic tasks administered in the same sequence across treatments. After controlling for both the willingness to pay for an object and the potential misperception of probabilities as elicited in the experiment, we detect no effect of alcohol in depleting subjects’ risk tolerance. However, we find that alcohol intoxication increases impatience and makes subjects less altruistic.

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.

The highs that bind: school context, social status and marijuana use

Substance use has been closely linked with the structural characteristics of adolescent social networks. Those who drink, smoke, and use drugs typically enjoy an elevated status among their peers. Rates of substance use vary substantially across schools, and indicators of school structure and climate account for at least part of this variation. Emerging research suggests peer-group processes are contingent on school context, but questions remain regarding the school-level mechanisms which condition the influence of network characteristics on substance use. The present study uses multilevel logistic regression models to examine the moderating influence of school connectedness, school drug culture, and global network density on the association between peer network status and marijuana use. The analyses draw on self, peer, and parental data from a sample of 7,548 high-school aged youth nested within 106 schools participating in the National Longitudinal Study of Adolescent to Adult Health (mean age = 15.2; % white = 59 %; male = 45 %). The results indicate that school connectedness significantly reduces the effect of social status on marijuana use. This provides evidence that school-level mechanisms can reduce the instrumentality of marijuana consumption in the status attainment process in adolescence.

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.

Addiction and Other Reasons Adolescent Smokers Give to Justify Smoking

BACKGROUND

The primary purpose of this paper is to examine youth addiction and other justifications for adolescent smoking, and how they affect the level of consumption.

METHODS

Data from the Spanish 'State Survey on Drug Use among High School Students' aged between 14 and 18 years old were used in this paper. To account for the nature of the cigarette consumption data, several count data models were estimated in order to select the one that best fits adolescent smoking consumption.

RESULTS

Most adolescent smokers smoke because it relaxes them, and about a quarter of them recognize that they are addicted. Moreover, the latter group smoke 44% more cigarettes than the rest (IRR = 1.444), revealing the strong addictive nature of tobacco, even at early ages. Moreover, parents' smoking increases the probability of smoking and has an impact on the level of consumption.

CONCLUSIONS

The implications of these findings offer insight for parents, researchers, educators, and cessation interventionists, as awareness of self-reported and other predictors held by smoking youth creates a vantage point to facilitate changes in smoking behavior.

Inequalities in social capital and health between people with and without disabilities

The poor mental and physical health of people with disabilities has been well documented and there is evidence to suggest that inequalities in health between people with and without disabilities may be at least partly explained by the socioeconomic disadvantage (e.g. low education, unemployment) experienced by people with disabilities. Although there are fewer studies documenting inequalities in social capital, the evidence suggests that people with disabilities are also disadvantaged in this regard. We drew on Bourdieu's conceptualisation of social capital as the resources that flow to individuals from their membership of social networks. Using data from the General Social Survey 2010 of 15,028 adults living in private dwellings across non-remote areas of Australia, we measured social capital across three domains: informal networks (contact with family and friends); formal networks (group membership and contacts in influential organisations) and social support (financial, practical and emotional). We compared levels of social capital and self-rated health for people with and without disabilities and for people with different types of impairments (sensory and speech, physical, psychological and intellectual). Further, we assessed whether differences in levels of social capital contributed to inequalities in health between people with and without disabilities. We found that people with disabilities were worse off than people without disabilities in regard to informal and formal networks, social support and self-rated health status, and that inequalities were greatest for people with intellectual and psychological impairments. Differences in social capital did not explain the association between disability and health. These findings underscore the importance of developing social policies which promote the inclusion of people with disabilities, according to the varying needs of people with different impairments types. Given the changing policy environment, ongoing monitoring of the living circumstances of people with disabilities, including disaggregation of data by impairment type, is critical.

High School Dropouts and Sexually Transmitted Infections

People who drop out of high school fare worse in many aspects of life. We analyze the relationship between dropping out of high school and the probability of contracting a sexually transmitted infection (STI). Previous studies on the relationship between dropout status and sexual outcomes have not empirically addressed unobserved heterogeneity at the individual level. Using fixed effects estimators, we find evidence supporting a positive relationship between dropping out of high school and the risk of contracting an STI for females. Furthermore, we present evidence that illustrates differences between the romantic partners of dropouts versus enrolled students. These differences suggest that female dropouts may be more susceptible to contracting STIs because they partner with significantly different types of people than non-dropouts. Our results point to a previously undocumented benefit of encouraging those at risk of dropping out to stay in school longer.

Alcohol consumption and social network ties among adolescents: evidence from Add Health

Although many studies have estimated the influence of peers on risky health behaviors, few have estimated the gains that adolescents receive from such behaviors, particularly in terms of social payoffs for complying with peer behavior. In this paper, we explore the extent to which alcohol consumption increases popularity of adolescents. Using data from a nationally-representative sample of adolescents, we estimate endogeneity-corrected models with school-level fixed effects to identify the effect of alcohol consumption on social network ties. We find that alcohol consumption leads to an increase in popularity, with the largest gains experienced by white males and females. Our results provide new evidence on the motivation behind adolescent drinking and have important implications for substance abuse interventions.

Peer effects on risky behaviors: new evidence from college roommate assignments

Social scientists continue to devote considerable attention to spillover effects for risky behaviors because of the important policy implications and the persistent challenges in identifying unbiased causal effects. We use the natural experiment of assigned college roommates to estimate peer effects for several measures of health risks: binge drinking, smoking, illicit drug use, gambling, having multiple sex partners, suicidal ideation, and non-suicidal self-injury. We find significant peer effects for binge drinking but little evidence of effects for other outcomes, although there is tentative evidence that peer effects for smoking may be positive among men and negative among women. In contrast to prior research, the peer effects for binge drinking are significant for all subgroups defined by sex and prior drinking status. We also find that pre-existing risky behaviors predict the closeness of friendships, which underscores the significance of addressing selection biases in studies of peer effects.

Adolescent mice, unlike adults, consume more alcohol in the presence of peers than alone

One hallmark of adolescent risk-taking is that it typically occurs when adolescents are with peers. It has been hypothesized that the presence of peers primes a reward-sensitive motivational state that overwhelms adolescents' immature capacity for inhibitory control. We examined this hypothesis using a rodent model. A sample of mice were raised in same-sex triads and were tested for alcohol consumption either as juveniles or as adults, with half in each age group tested alone and half tested with their cagemates. The presence of 'peers' increased alcohol consumption among adolescent mice, but not adults. The peer effect on human adolescent reward-seeking may reflect a hard-wired, evolutionarily conserved process through which the presence of agemates increases individuals' sensitivity to potential rewards in their immediate environment.

Risk-taking in social settings: Group and peer effects

We investigate experimentally the effect of consultation (unincentivized advice) on choices under risk in an incentivized investment task. We compare consultation to two benchmark treatments: one with isolated individual choices, and a second with group choice after communication. Our benchmark treatments replicate findings that groups take more risk than individuals in the investment task; content analysis of group discussions reveals that higher risk-taking in groups is positively correlated with mentions of expected value. In our consultation treatments, we find evidence of peer effects: decisions within the peer group are significantly correlated. However, average risk-taking after consultation is not significantly different from isolated individual choices. We also find that risk-taking after consultation is not affected by adding a feedback stage in which subjects see the choices of their consultation peers.

The role of family background on adolescent khat chewing behavior in Jazan Region

BACKGROUND

Khat is a well-known natural stimulant from the Catha edulis plant and is widely used in certain Red Sea countries, including Yemen and the province of Jazan in Saudi Arabia. Jazan is located in the southwestern part of the Kingdom of Saudi Arabia adjacent to Yemen, where the practice of khat chewing is deeply rooted throughout the entire population. The main objective of this paper was to assess the association between family background, i.e., parent and sibling khat use, and adolescents' khat chewing behavior in Jazan. Other variables were also tested for association, including parents' education levels, family income, and peer influence.

MATERIAL AND METHODS

A cross-sectional study was conducted with a representative sample (n = 4,100) of intermediate and upper secondary school students of Jazan. The participants were selected using a three-stage cluster random sampling. A structured self-administered questionnaire was used for data collection. Descriptive statistics, a chi-squared test, and logistic regression were performed to examine the associations and predictors of khat chewing.

RESULTS

A total of 3,923 students of both genders from 72 intermediate and upper secondary schools in Jazan were involved in this study. Of these participants, 42.8% (1,678) were from intermediate schools and 43.8% (1,717) were females. The prevalence of current khat chewing among the students was 20.5% (95% confidence interval (CI) 19.27-21.79) and was significantly higher for males at 33.1% (95% CI 31.16-35.08) than for females, of whom 4.3% (95% CI 3.39-5.31) (P < 0.001) chew khat. The multivariate logistic regression analysis suggests that the most important independent predictors of student khat chewing included the students' smoking status (odds ratio (OR) = 14.03, P < 0.001), a friend using khat (OR = 5.65, P < 0.001), a sister using khat (OR = 2.04, P < 0.05), a father using khat (OR = 1.45, P < 0.001), and a brother using khat (OR = 1.56, P < 0.05).

CONCLUSION

The results highlight the significant impact of peer and familial khat abuse in adolescent khat chewing behavior. The findings suggest that khat control programs need to focus on peers and family members to reduce the prevalence of the habit along with its unfavorable consequences.

Peer effects in adolescent BMI: evidence from Spain

This paper extends the recent literature on the influence of peers on adolescent weight on three new fronts. First, based on a survey of secondary school students in Spain in which peers are formed by nominated classmate friends, we find a more powerful positive and significant causal effect of friends' mean BMI on adolescent BMI than previous US-based research. These results are in line with international data, which show that peer group contact tends to vary across countries. Our findings cover a large set of controls, fixed effects, the testing of correlated unobservables, contextual influences and instrumental variables. Second, social interactions are identified through the property of intransitivity in network relationships. Finally, we report evidence of a strong, positive effect of peer pressure on several subgroups of adolescents in an attempt to study their vulnerability to social influences.

Why Do Some Irish Drink So Much? Family, Historical and Regional Effects on Students' Alcohol Consumption and Subjective Normative Thresholds

This paper studies determinants of drinking behavior and formation of subjective thresholds of acceptable drinking behavior using a sample of students in a major Irish University. We find evidence of strong associations between amounts of alcohol students consume and drinking of their fathers and older siblings. In contrast, we find little evidence of impacts of other non-drinking aspects of family background on students' drinking. Parental and older sibling drinking appears to affect subjective attitudes of students towards what constitutes problem drinking behavior. We investigated historical origins of drinking behavior including the role of the Church, English cultural influences, the importance of the brewery and distilling industry, and the influence of weather. We find relatively strong influences of the Catholic Church and English colonial settlement patterns on Irish drinking patterns but little influence of Irish weather. Historical licensing restrictions on the number of pubs and off-license establishments also appear to matter.

Proximal to distal correlates of the patterns of illicit drug use among night school students in Taiwan

This epidemiological study aimed to investigate illicit drug use by vocational high school night-class students in Taiwan to identify hypothesized proximal and distal factors associated with drug use patterns. Between September 2010 and January 2011, a randomized sample was drawn from 33 vocational high school night classes, enrolling 1079 students already employed outside campus. Subjects completed a validated self-reported questionnaire measuring proximal factors (biological, psychological, and behavioral) and distal factors (living with parents, parents' or siblings' use of legal substances, supervision by primary guardian, and perceived peer influence on drug use). Age, greater sensation-seeking behavior and legal substances use (i.e., tobacco and betel nuts) increased odds of being identified as experimental or regular users versus non-drug users. Higher rates of rule-breaking behavior were associated with increased odds of being identified as experimental users versus non-drug users. Among distal factors, only perceived peer influence on drug use was significantly associated with experimental and regular drug use. Proximal and distal factors were associated with drug use patterns among vocational high school night-class students. Influence factors identified may help vocational high school officials design effective illicit drug intervention programs for students with different drug use patterns.

Influence of grade-level drinking norms on individual drinking behavior

OBJECTIVE

To investigate which points of the middle-school drinking distribution are the most influential in the social contagion of drinking across the middle-school years, in order to identify potential social multipliers.

METHODS

We measured drinking intentions and behaviors by gender, school, and grade among urban middle-school students who participated in Project Northland Chicago in a longitudinal cohort design.

RESULTS

Individual drinking behaviors were consistently influenced by extreme (80(th) percentile) drinking intentions and behaviors. This effect was mediated through normal or average levels of drinking, over time.

CONCLUSIONS

Interventions can target extreme drinkers as the influential persons in middle-school grades.

Consumo de substâncias ilícitas por adolescentes portugueses

OBJETIVO: Descrever a prevalência de consumo de drogas ilícitas em adolescentes e os motivos que os levam a experimentá-las. MÉTODOS: Estudo transversal com 2.499 adolescentes de 17 anos, com base numa coorte designada por EPITeen, iniciada em 2003/2004 com adolescentes nascidos em 1990 que estudavam nas escolas públicas e privadas da cidade do Porto, Portugal. Foi realizada nova avaliação em 2007/2008, sendo recuperados 1.716 adolescentes (79,4%) e avaliados 783 novos participantes. Informações sobre características sociais e demográficas, história familiar e pessoal de doença e comportamentos foram obtidas com questionários estruturados autoadministrados. O teste de qui-quadrado foi utilizado para testar as associações. A análise estatística foi realizada no programa informático SPSS® versão 17. RESULTADOS: Dos adolescentes, 14,6% referiram ter experimentado drogas alguma vez na vida. A droga ilícita mais experimentada foi a cannabis (12,5%), seguida pelo álcool em simultâneo com cannabis (5,5%) e pelos tranquilizantes (1,7%). A razão mais referida para experimentar drogas foi a curiosidade (77,5%). Os amigos foram a forma mais frequentemente referida para obter a droga e a escola era vista por 24,2% dos adolescentes como um local em que se podia comprar cannabis. CONCLUSÕES: Os resultados fundamentam a necessidade de intervir em idades precoces e sugerem que essa intervenção deve ser integrada com estratégias dirigidas a outros comportamentos de risco, nomeadamente em meio escolar.

Alcohol use and abuse among rural Zimbabwean adults: a test of a community-level intervention

BACKGROUND

Understanding what factors contribute to alcohol abuse in resource-poor countries is important given its adverse health consequences. Past research shows that social peers influence substance abuse, suggesting that the social environment may be an effective target for reducing alcohol abuse across a population. This study investigates the determinants of alcohol use and abuse in rural Zimbabwe and tests a community popular opinion leader (CPOL) community-based intervention partly directed at reducing alcohol abuse.

METHODS

Tests were conducted on the impact of the CPOL intervention on alcohol use patterns across communities in rural Zimbabwe over three waves from 2003 to 2007, including community- and individual-level tests using data based on in-person interviews of adult men and women (ages 18-30; N=5543). Data were analyzed using paired-sample t-tests, as well as logistic and ordinary least-squares regression with random effects.

RESULTS

Higher drinking (any use, more frequent use, greater quantity, and/or frequent drunkenness) was generally associated with being male, older, not married, more highly educated, of Shona ethnicity, away from home frequently, employed, having no religious affiliation, or living in areas with a higher crude death rate or lower population density. Over the study period, significant declines in alcohol use and abuse were found in intervention and control sites at relatively equal levels.

CONCLUSIONS

Although no support was found for the effectiveness of the CPOL study in reducing alcohol abuse, Zimbabwe is similar to other countries in the impact of socio-demographic and cultural factors on alcohol use and abuse.

Similarity in peer college preferences: New evidence from texas

In this paper, I use survey data from high school students in Texas to examine the magnitude of peer correlation in college preferences and choices. In this survey, respondents (and their classmates) recorded their preferences for attending specific colleges, and a follow up survey recorded their college enrollment decisions. This paper uses this information to present the first empirical examination of whether individuals who report preferences for "popular" colleges are more likely to attend their preferred college. The rich data set allows the use of often unavailable information such as distance to college, and the construction of the "popularity" variable allows the use of school-level fixed effects. Results indicate that individuals with 10 percentage points more classmates with matching college preferences are 3 percentage points more likely to enroll in their preferred college.

Can fantasizing while listening to music play a protective role against the influences of sensation seeking and peers on adolescents' substance use?

"The combination of music and drugs proved to be potent, and scientific research has yet to explain it" (Levitin, 2008, p. 74; The World in Six Songs). This study examined if fantasizing while listening to music could represent a potential protective factor against adolescent substance use (cigarette, alcohol, and cannabis). The first hypothesis was that fantasizing while listening to music would moderate (buffer) the link between sensation-seeking and substance use. The second hypothesis was that fantasizing while listening to music would also moderate (buffer) the link between peer substance use and individual substance use. The sample comprised 429 adolescent boys and girls who answered a self-report questionnaire in 2003. They were regular students attending a public high school in Montreal, Canada. The results revealed that fantasizing while listening to music came short of buffering the link between sensation-seeking and substance use among highly musically involved adolescents. Still, fantasizing while listening to music significantly attenuated the relationship between peer substance use and individual substance use (thereby, showing a protective effect) among highly musically involved adolescents. Fantasizing while listening to music did not buffer the relation between either risk factor (sensation-seeking or peer substance use) and substance use among moderately musically involved adolescents.

Junk Food in Schools and Childhood Obesity

Despite limited empirical evidence, there is growing concern that junk food availability in schools has contributed to the childhood obesity epidemic. In this paper, we estimate the effects of junk food availability on BMI, obesity, and related outcomes among a national sample of fifth-graders. Unlike previous studies, we address the endogeneity of the school food environment by controlling for children's BMI at school entry and estimating instrumental variables regressions that leverage variation in the school's grade span. Our main finding is that junk food availability does not significantly increase BMI or obesity among this fifth grade cohort despite the increased likelihood of in-school junk food purchases. The results are robust to alternate measures of junk food availability including school administrator reports of sales during school hours, school administrator reports of competitive food outlets, and children's reports of junk food availability. Moreover, the absence of any effects on overall food consumption and physical activity further support the null findings for BMI and obesity.

Distal and proximal family predictors of adolescents' smoking initiation and development: a longitudinal latent curve model analysis

Background

Studies on adolescent smoking indicate that the smoking behaviours of their parents, siblings and friends are significant micro-level predictors. Parents' socioeconomic status (SES) is an important macro-level predictor. We examined the longitudinal relationships between these predictors and the initiation and development of adolescents' smoking behaviour in Norway.

Methods

We employed data from The Norwegian Longitudinal Health Behaviour Study (NLHB), in which participants were followed from the age of 13 to 30. We analysed data from the first 5 waves, covering the age span from 13 to 18, with latent curve modeling (LCM).

Results

Smoking rates increased from 3% to 31% from age 13 to age 18. Participants' smoking was strongly associated with their best friends' smoking. Parental SES, parents' smoking and older siblings' smoking predicted adolescents' initial level of smoking. Furthermore, the same variables predicted the development of smoking behaviour from age 13 to 18. Parents' and siblings' smoking behaviours acted as mediators of parents' SES on the smoking habits of adolescents.

Conclusions

Parents' SES was significantly associated, directly and indirectly, with both smoking initiation and development. Parental and older siblings' smoking behaviours were positively associated with both initiation and development of smoking behaviour in adolescents. There were no significant gender differences in these associations.

Alcohol Use and Popularity: Social Payoffs from Conforming to Peers' Behavior

Although many economic analyses of adolescents have examined the costs of risky behaviors, few have investigated the gains that young people derive from such actions, particularly in terms of social payoffs for complying with peer behavior. This paper studies the relationship between adolescents' use of alcohol (relative to that of their peers) and popularity at school. We use data from the National Longitudinal Study of Adolescent Health, a rich and nationally-representative survey with detailed information on social networks. Our findings suggest that adolescents are socially rewarded for conforming to their peers' alcohol use and penalized (to a lesser degree) for increasing their consumption above that of their peers. Male adolescents are rewarded for keeping up with their peers' drinking and for getting drunk. Female adolescents are rewarded for drinking per se, but not necessarily for keeping up with their peers. The results offer new information on peer influence and have implications for substance abuse interventions at school and in the community.

Estimates of peer effects in adolescent smoking across twenty six European countries

Although it is widely believed that one of the key factors influencing whether an adolescent smokes or not is the smoking behaviour of his or her peers, empirical evidence on the magnitude of such peer effects, and even on their existence, is mixed. This existing evidence comes from a range of studies using a variety of country-specific data sources and a variety of identification strategies. This paper exploits a rich source of individual level, school-based, survey data on adolescent substance use across countries--the 2007 European Schools Survey Project on Alcohol and Other Drugs--to provide estimates of peer effects between classmates in adolescent smoking for 75,000 individuals across 26 European countries, using the same methods in each case. The results suggest statistically significant peer effects in almost all cases. These peer effects estimates are large: on average across countries, the probability that a 'typical' adolescent smokes increases by between .31 and .38 percentage points for a one percentage point increase in the proportion of classmates that smoke. Further, estimated peer effects in adolescent smoking are stronger intra-gender than inter-gender. They also vary across countries: in Belgium, for example, a one percentage point increase in reference group smoking is associated with a .16 to .27 percentage point increase in own smoking probability; in The Netherlands the corresponding increase is between .42 and .59 percentage points.

Schooling and smoking among the baby boomers - an evaluation of the impact of educational expansion in France

Post-war expansion of education in France transformed the distribution of schooling for the cohorts born between the 1940s and the 1970s. However, throughout this expansion the proportion with the highest levels of qualifications remained stable, providing a natural control group. We evaluate the impact of schooling on smoking, for the beneficiaries of the post-war expansion, by comparing changes in their outcomes across birth cohorts with changes within the control group. We uncover robust evidence that educational expansion contributed to a decline in smoking prevalence of 2.9 points of percentage for men and 3.2 points for women at the turn of the 21st century. Our results also suggest that the persistence of the schooling-smoking gradient is better explained by differences in the education-related opportunity costs of smoking than by differences in information about smoking dangers.

Peer effects and the freshman 15: evidence from a natural experiment

This study investigates the importance of peer effects in explaining weight gain among freshman college students. We exploit a natural experiment that takes place on most college campuses in the US--randomized roommate assignments. While previous studies suggest that having an obese spouse, friend, or sibling increases one's likelihood of becoming obese, these social interactions are clearly non-random. We collect data from female students living on campus at a private Midwestern university at the beginning and end of their first year of college. Our findings suggest that the amount of weight gained during the freshman year is strongly and negatively correlated to the roommate's initial weight. Further, our analysis of behaviors suggests that female students adopt some of their roommates' weight-loss behaviors which cause them to gain less weight than they otherwise would have. In particular, we find evidence that this effect may be through influences in eating, exercise, and use of weight loss supplements.

That instrument is lousy! In search of agreement when using instrumental variables estimation in substance use research

The primary statistical challenge that must be addressed when using cross-sectional data to estimate the consequences of consuming addictive substances is the likely endogeneity of substance use. While economists are in agreement on the need to consider potential endogeneity bias and the value of instrumental variables estimation, the selection of credible instruments is a topic of heated debate in the field. Rather than attempt to resolve this debate, our paper highlights the diversity of judgments about what constitutes appropriate instruments for substance use based on a comprehensive review of the economics literature since 1990. We then offer recommendations related to the selection of reliable instruments in future studies.

The social contagion effect of marijuana use among adolescents

BACKGROUND

Research on adolescent substance use has consistently identified a strong relationship between adolescent behavior and the behavior of their peers. However, peer effects are difficult to estimate and causal interpretations must be undertaken with caution since individuals in most cases choose with whom to associate. In this paper we seek to empirically quantify the causal role of peer social networks in explaining marijuana usage among adolescents.

METHODS AND FINDINGS

Using data from a nationally representative sample of adolescents we utilize a multivariate structural model with school-level fixed effects to account for the problems of contextual effects, correlated effects and peer selections to purge the potential biases from the estimates of peer influence. Our peer group measures are drawn not only from the nomination of close friends (N = 6,377), but also from classmates (N = 19,335). Marijuana usage among the peer groups were constructed using the peers' own report of their marijuana consumption. Controlling for parent level characteristics, and other demographic parameters, we find that a 10% increase in the proportion of close friends and classmates who use marijuana increases the probability that an individual chooses to use marijuana by 5%.

CONCLUSION

Our findings indicate that peer effects are important determinants of marijuana use even after controlling for potential biases We also found evidence to show that the influence of close friends and the more exogenous classmates are quite similar in magnitude under our preferred specification, supporting theory predicting the importance of peer influence. Effective policy aimed at reducing marijuana usage among adolescents would consider these significant peer effects.

Adolescent smoking risk increases with wider income gaps between rich and poor

Data from a state-wide survey of California middle and high school students (N=20,203) were used to assess whether county income inequality and poverty rates were associated with adolescent smoking. Greater county income inequality, but not poverty rates, was associated with higher established smoking risk (p=0.0019). The association was stronger in males than females, whites than other ethnic groups, and urban than rural settings. Neither county income inequality nor poverty rates were associated with experimental smoking. The findings suggest that it may be important to consider and address economic inequality in the prevention and control of adolescent tobacco use.

Social Relationships and Health Behavior Across Life Course

Sociological theory and research point to the importance of social relationships in affecting health behavior. This work tends to focus on specific stages of the life course, with a division between research on childhood/adolescent and adult populations. Yet recent advances demonstrate that early life course experiences shape health outcomes well into adulthood. We synthesize disparate bodies of research on social ties and health behavior throughout the life course, with attention to explaining how various social ties influence health behaviors at different life stages and how these processes accumulate and reverberate throughout the life course.

Social interactions and smoking: evidence using multiple student cohorts, instrumental variables, and school fixed effects

In this paper, I use a social interactions framework to detect whether individual smoking decisions are influenced by classmate smoking decisions. There are several large challenges in addressing this question, including the endogeneity of school (and thus classmates) through residential location choices, 'third factors' such as school-level unobservables that influence individual and classmate choices simultaneously, and the difficulty of the identification of parameters in empirical models of social interactions. In order to address these issues, I use an instrumental variables/fixed effects methodology that compares students in different grades within the same high school who face a different set of classmates and classmates' decisions. Preferred specifications suggest that increasing the proportion of classmates who smoke by 10% will increase the likelihood an individual smokes by approximately 3 percentage points. I compare these results with previous findings that are unable to use school fixed effects and/or use potentially invalid instruments and find that the current results suggest smaller social interactions in adolescent smoking decisions than some previous work.

Social network effects in alcohol consumption among adolescents

In this paper we seek to empirically quantify the role of peer social networks in explaining drinking behavior among adolescents. Using data from a nationally representative sample of adolescents we utilize a multivariate structural model with school-level fixed effects to account for the problems of contextual effects, correlated effects and peer selection to purge the potential biases from the estimates of peer influence. Our peer group measures are drawn not only from the nomination of close friends, but also from classmates. Drinking behavior among the peer groups was constructed using the peers' own report of their alcohol consumption. Controlling for parent level characteristics, and other demographic parameters, we find that a 10% increase in the proportion of classmates who drink will increase the likelihood of drinking participation and frequency by approximately four percentage points. We also find evidence to show that the influence of close friends, while still significant, diminishes in magnitude after accounting for unobserved environmental confounders. Our findings support the literature that peer effects are important determinants of drinking behavior even after controlling for potential biases. Effective policy aimed at reducing alcohol consumption among adolescents would consider these significant peer effects.

Estimating the determinants of smoking behavior in Taiwan

This paper investigates the determinants of the smoking behavior of people in Taiwan based on data obtained from the 2004 Taiwan Panel Study of Family Dynamics. The sample size consists of 3,015 individuals whose ages range from 33 to 75. Probit models are estimated separately for the smoking behavior equations. The results indicate that gender, marital status, age, health, employment, and the presence of young children have a relatively important impact on an individual's smoking behavior. In addition, the results of the estimated predictors, such as having higher educational attainment, having smoking family members and smoking peers, and being aware of the harmful effects of smoking, also bring to light crucial policy implications. Study limitations are noted.

Estimating peer effects in sexual behavior among adolescents

In this paper we seek to empirically quantify the role of peer social networks in influencing sexual behavior among adolescents. Using data of a nationally representative sample of adolescents we utilize a multivariate structural model with school-level fixed effects to account for the problems of contextual effects, correlated effects and peer selections to purge the potential biases from the estimates of peer influence. Our peer group measures are drawn not only from the nomination of close friends, but also from classmates. Controlling for parent level characteristics, and other demographic parameters, we find that a 10% increase in the proportion of close friends who initiates sex increases the probability that an individual chooses to initiate sex by 5% and a 10% increase in number of sexual partners among close friends increases an individual's sexual partner by 5%. The influence of classmates however, diminishes in magnitude after accounting for unobserved environmental confounders.

The influence of peers on risky sexual behaviour during adolescence

OBJECTIVES

To determine to what degree the predominance of risky sexual behaviour during adolescence is the result of social influence, in particular that of peers, according to the perception of their attitudes and sexual behaviour.

METHODS

Data were collected through structured and confidential individual interviews with 100 adolescents, selected randomly from among 1467 students attending one French high school.

RESULTS

Although this study is of an exploratory nature, it reveals that the perception of peers is associated with a higher frequency of sexual initiation and commitment, including oral sex, but also commitment to protected sex. Sexual permissiveness of peers is associated with a higher frequency of sexual practices considered risky. The attitudes of peers with regard to contraception are associated with protective contraceptive attitudes, without a direct influence on behavioural patterns.

CONCLUSIONS

The sexual norms of peers influence youths' individual attitudes and behaviours. Gender differences in sexual socialization also play a role. Both aspects must be taken into account when devising prevention programmes concerning adolescent sexuality.

The effect of friends on adolescent body weight

Using the first wave of the National Longitudinal Study of Adolescent Health (Add Health) survey, this paper examines the influence of peers on adolescent weight. A peer group is defined as a close circle of friends that are identified by a respondent adolescent. After controlling for school fixed effects and for a number of individual, demographic and family characteristics, we find that a higher Body Mass Index (BMI) of close friends is correlated to a higher BMI of the respondent adolescent. However, after instrumental variable analysis is performed, the effect remains significant only among women. We also found that adolescents are more responsive to the body weight of their same gender friends.