Fragmentation or integration? Ethnic diversity and the structural cohesion of adolescent social networks

Clustering and Cohesion in Networks: Concepts and Measures

The detection of structural cohesion is a key utility of social network analysis, but little work has been done to refine the detection of structural cohesion in two-mode networks. Most work on cohesion in two-mode networks either: (1) attempts to detect cohesion in such networks using one-mode projections (which can be problematic for reasons we discuss); or (2) focuses on restrictive substructures like bi-cliques to identify cohesive subgroups. We propose a new strategy for two-mode networks that follows the general reasoning of approaches to detecting structural cohesion in one-mode networks. Our approach identifies the number of actors from one node set that may be removed before disconnecting actors in the opposite set. We also develop a definition of embeddedness that draws on Moody and White’s hierarchical nesting approach.

Together We Can Improve Outcomes in Kidney Failure: Examining Social Networks in Hemodialysis

The current study's purpose is to explore the influence of peer-perceived creativity (sociometric creativity) on the short-term development of friendships during a summer program for high ability students. Specifically, the two main objectives of our study are: (1) How did students' friendships network and sociometric creativity network evolve in the summer program? (2) How did sociometric creativity influence the friendship formation? The longitudinal study was conducted at the beginning, middle and the end of a 3-week long program for gifted students in Ireland. The sample consisted of Irish gifted students (N = 702, aged 13-18 years, 52% female, over thirty-one classes). Overall, our longitudinal multilevel and multigroup social network analysis shows that gifted adolescents formed reciprocated friendship ties and cohesive peer group structures in the investigated period; similar age and the same gender predicted friendship formation. Regarding the sociometric creativity, they tended to nominate a similar age and same gender student as very creative. Moreover, the sociometric creativity positively influenced adolescents' friendship networks on a dyadic level, indicating that adolescents select friends based on their perception of the other student's creativity. Further results, explanations, and implications are discussed.

Community search is a method of finding a com-munity closely related to a query node. The latest influence community search considers both the structural cohesion of the community and the influence between nodes. It sets the influence threshold to constrain the output community. However, artificially setting the influence threshold makes the output community too large or too small, which leads to low accuracy of the output community. In order to avoid the low accuracy of community search caused by artificially setting influence thresh-old constraints, this paper studies the community search problem based on community influence score. In this paper, an influence-truss community (ITC) model is proposed for community search by combining structural cohesion and community influence score. This model aims to obtain a connected subgraph in a social network containing the query node, which satisfies structural cohesion and satisfies the subgraph's maximum community in-fluence score. In order to obtain ITC, an effective pruning method is proposed, which strips other nodes far away from the query node. Then, the ITCS algorithm is designed, which firstly imposes structural cohesion constraints on query nodes. Then, the search community's influence scores are iteratively calculated until the community has the highest community influence score under the condition of meeting the structural cohesion. Experiments on real-world networks of different scales show that the community search accuracy index of ITCS is improved by about 20% compared with the traditional method.

Social network analysis has been postulated as a tool to study potential pathogen transmission in wildlife but is resource-intensive to quantify. Networks based on bacterial genotypes have been proposed as a cost-effective method for estimating social or transmission network based on the assumption that individuals in close contact will share commensal bacteria. However, the use of network analysis to study wild populations requires critical evaluation of the assumptions and parameters these models are founded on. We test (a) whether networks of commensal bacterial sharing are related to hosts' social associations and hence could act as a proxy for estimating transmission networks, (b) how the parameters chosen to define host associations and delineate bacterial genotypes impact inference and (c) whether these relationships change across time. We use stochastic simulations to evaluate how uncertainty in parameter choice affects network structure. We focused on a well-studied population of eastern grey kangaroos (Macropus giganteus), from Sundown National Park, Australia. Using natural markings, each individual was identified and its associations with other kangaroos recorded through direct field observations over 2years to construct social networks. Faecal samples were collected, Escherichia coli was cultured and genotyped using BOX-PCR, and bacterial networks were constructed. Two individuals were connected in the bacterial network if they shared at least one E.coli genotype. We determined the capacity of bacterial networks to predict the observed social network structure in each year. We found little support for a relationship between social association and dyadic commensal bacterial similarity. Thresholds to determine host associations and similarity cut-off values used to define E.coli genotypes had important ramifications for inferring links between individuals. In fact, we found that inferences can show opposite patterns based on the chosen thresholds. Moreover, no similarity in overall bacterial network structure was detected between years. Although empirical disease transmission data are often unavailable in wildlife populations, both bacterial networks and social networks have limitations in representing the mode of transmission of a pathogen. Our results suggest that caution is needed when designing such studies and interpreting results.

In this study, Social Network Analysis method was used to determine the professional relationships, friendships and trust networks that teachers established with their colleagues. The study group of the research consists of 35 teachers working in a public secondary education institution in Aydın province. A three-question structured interview form developed by the researchers was used to determine teachers' social networks. Data analysis was carried out through the UCINET 6.0 program. When the findings regarding the positions of teachers in the professional relationship network, friendship network and trust network were examined, it was determined that the network structure with the highest number of connections was the friendship network (ties = 97), followed by the professional relationship (ties = 95) and the trust network (ties = 66). In all social networks, teachers with mathematics, guidance, literature and biology branches were found to be at the center of the network, acting as a bridge between other actors and providing information and resource flow. According to the findings, it was determined that the network with the highest density (dens. = 0.082), bilateral (dia. = 0.198) and triad (triad = 0.330) reciprocity rate was the friendship network. This study, which examines the professional relationships, friendships and trust networks that teachers establish with their colleagues, is thought to be important in revealing the relationships between teachers and analyzing the current situation.

This study examined the relationship between employees' social network positions and their psychological contract beliefs. In particular, it investigated the relationship of employee advice and friendship ties with their employer's relational (long-term, non-monetizable), balanced (performance-related), and transactional (short-term, monetizable) obligations to them. Data obtained from a start-up research firm showed that employees brokering structural holes in the advice network believed the firm had greater balanced and transactional obligations to them. Employees with cohesive ties in the friendship network also believed that the firm owed them more balanced and transactional obligations. Neither structural holes nor cohesion were related to relational obligations. This study develops implications for psychological contracts and social networks research.

The role of social networks: A novel hypothesis to explain the phenomenon of racial disparity in kidney transplantation

: Social Network Analysis for Assessing Social Capital in Biosecurity Ecoliteracy. Biosecurity ecoliteracy (BEL) is a view of literacy that applies ecological concepts to promote in-depth understanding, critical reflection, creative thinking, self consciousness, communication and social skills, in analyzing and managing issues around plant health/living, animal health/living and the risks that are associated with the environment. We used social network analysis (SNA) to evaluate two distinct forms of social capital of BEL: social cohesion and network structure. This study was executed by employing cooperative learning in BEL toward 30 undergraduate teacher training students. Data then was analyzed using UCINET software. We found the tendency of so­cial cohesion to increase after students participated in BEL. This was supported by several SNA measures (density, closeness and degree) and these values at the end were statistically different than at the beginning of BEL. The social structure map (sociogram) after BEL visualized that students were much more likely to cluster in groups compared with the sociogram before BEL. Thus BEL, through cooperative learning, was able to promote social capital. In addition SNA proved a useful tool for evaluating the achievement levels of social capital of BEL in the form of network cohesion and network structure.

An analysis of friendship networks, social connectedness, homesickness, and satisfaction levels of international students

User engagement has recently received significant attention in understanding decay and expansion of communities in social networks. However, the problem of user engagement hasn't been fully explored in terms of users' specific interests and structural cohesiveness altogether. Therefore, we fill the gap by investigating the problem of community engagement from the perspective of attributed communities. Given a set of keywords W, a structure cohesive parameter k, and a budget parameter l, our objective is to find l number of users who can induce a maximal expanded community. Meanwhile, every community member must contain the given keywords in W and the community should meet the specified structure cohesiveness constraint k. We introduce this problem as best-Anchored Vertex set Exploration (AVE).To solve the AVE problem, we develop a Filter-Verify framework by maintaining the intermediate results using multiway tree, and probe the best anchored users in a best search way. To accelerate the efficiency, we further design a keyword-aware anchored and follower index, and also develop an index-based efficient algorithm. The proposed algorithm can greatly reduce the cost of computing anchored users and their followers. Additionally, we present two bound properties that can guarantee the correctness of our solution. Finally, we demonstrate the efficiency of our proposed algorithms and index. We measure the effectiveness of attributed community-based community engagement model by conducting extensive experiments on five real-world datasets.

Perceived group cohesion versus actual social structure: A study using social network analysis of egocentric Facebook networks

Introduction Peter Piot (Executive Director of UNAIDS) challenged Bangkok International AIDS Conference attendees to think ahead 10 years or more so we will be prepared to meet the challenges that will face us [1]. Over this next decade, many formidable challenges are likely to stem from the interactions of social, ecological, political, and economic change; existing social structures; the changing HIV epidemic, and changes produced by emerging biomedicine and viral evolution. Although some challenges will be unpredictable, we should plan ahead for those we are able to anticipate. This paper identifies important social research issues regarding the changing global epidemic so funding agencies, journal editors, social science communities, individual researchers and students, non-governmental organizations, community-based organizations, and the general public can debate them and, hopefully, act on them. Social change is likely to create complex problems for our response to HIV. Weiss and McMichael [2] demonstrate the acceleration of socially-driven epidemic outbreaks of infectious diseases in recent years. As Rischard has argued [3,4], there is a high probability of massive political, ecological and social changes over the next few years. These threaten large-scale disruption of existing social and risk networks, sexual (and injection) mixing patterns, and sexual and injection behaviors that can impede or facilitate HIV transmission – and thus might generate HIV outbreaks parallel to those that followed the disruption of the USSR or that seem to be resulting from the increasing 'globalization' of India and China [5]. Global warming could produce large-scale population movements with similar results. Our reflections here on social change and other possible transformations have not produced a comprehensive or complete list of social research priorities. We have emphasized 'macro' and middle-level processes focusing on social, economic, political and cultural factors that affect HIV spread and/or that influence responses to the threat of HIV (rather than on small group or individual level processes that focus on the psychological and interpersonal) because we think these have received relatively less attention than is needed. We recognize that other researchers might produce different lists. We also recognize that it is important to foreground the probability that socio-epidemiologic contexts are likely to continue to have great cross-national variation and that 'big events' such as wars and transitions, perhaps in interaction with religious revival movements, can rapidly move countries into crisis conditions that pose the threat of explosive HIV outbreaks. Such changes can occur in countries that currently appear politically and economically stable. (It is useful to remember that few analysts in the early 1980s foresaw either the fall of the USSR or the collapse of apartheid in South Africa). The HIV/AIDS epidemic is itself a 'big event' in localities with high prevalence. While acknowledging the above, we propose six major emerging social research issues or themes. These themes, organized in terms of selected social and epidemiologic processes and situations (although noting that research on each of these topics will have at least some relevance everywhere), concern the following items. Wars, transitions, ecological or economic disruptions. Large-scale HIV epidemics, their related illness and death, and their attendant social instability and social disruption. Government policies that ignore or defy available evidence. Stable societies without generalized epidemics, which face distinctive challenges. Emerging biomedicine and its attendant opportunities and (perhaps unintended) social consequences. Possible failure of previously effective therapies due to viral evolution or disruptions in patterns of social organization. Each of these six themes provokes a number of research questions. To answer these questions, the full armamentarium of social science and social epidemiologic research methods will be needed, including theory development; hypothesis-testing and exploratory studies; ethnographic, quantitative, historical, and comparative designs; and intervention trials. In all of these approaches, involving relevant community members, decision-makers, and other actors as full collaborators or as sources of guidance, inspiration or critique, can be invaluable, including those based on participatory action research and on collaborative systematization of experiences [6–8]. Research has documented the effectiveness of community responses to HIV – often in advance of public health interventions [9]. Working with communities means that interventions are informed by community members and are thus more likely to be perceived as appropriate and taken up. However, throughout the epidemic, there has been a relative lack both of researchers interested in topics like those in these six themes and of funding to conduct such research. We close with thoughts about how to address these problems. Social processes and HIV/AIDS Why should social factors affect HIV/AIDS epidemics? The first reason is that HIV is transmitted through sexual and drug-injection networks, which are fundamentally social phenomena. Social norms about appropriate choice, numbers and timing of partners, and about behaviors with those partners, shape crucial network variables such as concurrent sexual and injection partnerships; partner turnover rates; mixing patterns; the size, centrality and microstructures of community network components; and the extent of quasi-anonymous risk nodes such as group sex parties, bath-houses, and shooting galleries [5,10–16]. Social norms, regulations, educational systems and law enforcement processes affect sexual and drug-taking behaviors [17,18]. Social networks, norms and social support shape how people access, interpret and use HIV-prevention information and education, the extent to which people make use of sexually transmitted disease treatments and HIV therapies, HIV counseling and testing, and affect adherence to therapies [19–21]. Economic and political conditions and dynamics affect what services are available and how inconvenient, costly, or stigmatizing it is to use them [22–31]. Finally, events, including large-scale epidemics themselves, that disrupt local or national social networks, communities, services, or social norms, lead to large-scale migration, or initiate large-scale mixing across new sexual or injecting networks, create the potential for risk behaviors or adherence failures that would have previously been prevented – and these, in turn, might lead to epidemic outbreaks [e.g., 32]. Emerging research issues for different processes and situations (A) Wars, transitions, ecological or economic disruptions Aral [5], Hankins et al. [33], and Friedman and Reid [34] have argued that transitions – like those in the former Soviet Union circa 1990, South Africa in the early 1990s, and Indonesia in the late 1990s – and wars can disrupt risk networks and protective social norms and thus lead to HIV outbreaks. However, such outbreaks are not inevitable. Gisselquist [35] and Spiegel [36] show that many African wars have not increased HIV transmission, and the case of the Philippines shows that transitions need not lead to outbreaks either. Furthermore, United States involvement in wars since the early 1990s seems not yet to have accelerated HIV transmission there. Although further research on whether wars or transitions are statistical risk factors for increases may be useful, we suggest that the historical record is strong enough to conclude that both wars and transitions can, on occasion, lead to epidemic outbreaks of HIV – that is, under some conditions, they increase social vulnerability to HIV [37–39]. On the other hand, under other conditions, outbreaks do not occur. This suggests that the following research questions should receive high priority. To identify which pre-existing conditions (including but not limited to gender relationships, sexual culture, and patterns of psychoactive drug use) and social processes can lead to increased HIV vulnerability as a consequence of war, transitions, or, perhaps, of economic breakdown or of ecological change such as global warming [40]. Such research should study how these events: (a) shape norms, behaviors, practices, and sexual, injection and care networks; and (b) affect gender and racial/ethnic power relationships, religious belief systems, poverty, and other middle-level socio-cultural and political economic relationships that influence HIV transmission and the capacity for prevention and care. To consider how affected populations or outsiders might intervene to avert or reduce epidemic outbreaks due to wars, transitions, or other events; and how such responses are shaped by pre-existing social identities, community resilience, patterns of social and political co-operation, and indigenous leadership [41–43]. In terms of research designs, much might be learned from qualitative and quantitative studies that compare countries that did and did not have outbreaks subsequent to such events; that study localities that did not have outbreaks within countries that did; and perhaps by rapid-response research teams that work with local participants and researchers to study emerging prevention efforts, network patterns, behaviors, pockets of emerging high-risk practices, and medical services, together with HIV and sexually transmitted infection rates, during and after wars and transitions. (B) Large-scale HIV epidemics, their related illness and death, and their attendant social instability and social disruption Just as wars, transitions and other processes can disrupt social norms and social, sexual and drug-use networks and communities, HIV/AIDS epidemics large enough to constitute socially-disruptive 'big events' can have similar effects. The research questions that are raised under (A) are also important in these circumstances. The exact definition of 'large enough' probably depends on the rate of spread of HIV over time and also on its socio-economic distribution – and research on how much disruption results from different prevalences and distributions of the virus might be useful. Research is also needed on how to minimize the destruction and maximize the constructive outcomes of social crises that the epidemic produces. Given the extent of HIV in many African countries, and its potential spread in Asia, the emerging social research issues for this context are clearly important [see, for example, 44–51]. These may include the following items. To identify and describe mid-level social forces (such as gender or racial/ethnic power relationships, religious conditions and beliefs, community resilience, and poverty) that create, sustain or reduce high-risk sexual or injection network patterns or behaviors that contribute to high HIV transmission rates – and, most important, to determine how to intervene in these. To describe possible impacts of the epidemic in terms of changes in social, sexual and drug-use networks, norms, culture, gender relationships, community resilience, etc. – and to determine what actions by local and outside agencies and by affected populations can mitigate further infections and social distress. To consider how affected populations and agencies might intervene or organize against individual, community and institutional stigma [52,53]. To determine how populations can be mobilized for risk reduction before mass illness or dying begin. To establish how health systems can be organized for disease control and care in poor countries or under conditions of disruptively high mortality. How can affected and unaffected populations assist in this? How can these efforts be sustained in contexts of socially-disruptive high morbidity and mortality? To determine how to navigate the AIDS crisis so that negative social consequences are minimized and positive social gains initiated or maintained. This question – monumental in scope – has been raised by Mary Crewe and her colleagues [54], and requires both scholarly input and popular action to resolve. (C) Government policies that ignore or defy available evidence Governments' responses to HIV and other health-related issues, and how they are shaped by social structures, competing priorities, and resource availability, are important to study. We emphasize here one aspect of this issue that has been important in the HIV/AIDS epidemic – government policies that ignore or defy available evidence. Since HIV is transmitted by culturally and religiously-sensitive and often, legally prohibited, behaviors, and since government health and policing policies on sex, reproduction, and illicit drug use may themselves contribute to HIV spread and/or to the failure to treat HIV, it is unsurprising that governments sometimes do not implement programs that research has determined to be effective. United States policies on syringe exchange, sex education in schools, programs for sex workers, and intellectual property rights are examples of this [18,55–57], as are the failure of many governments to introduce large-scale methadone programs for opiate users [27] and South Africa's failure for many years to accept that HIV was the proximate cause of the epidemic [58]. Despite this widespread pattern, there has been too little research on the following issues. Why governments ignore and/or flout scientific findings. Effective ways in which internal and external forces can act to change these policies. These are likely to vary depending on the reasons why each government acts this way and on economic, political and other contexts that affect governmental decision-making, including how mass media shape public agendas around HIV/AIDS [59]. (D) Stable societies without generalized epidemics A number of research issues exist for these societies [60,61]. Importantly, although countries such as the Netherlands, Brazil or Saudi Arabia can currently be classified as stable and without generalized HIV epidemics, HIV could spread rapidly under social crises such as those Rischard [3,4] identified, or, indeed, under conditions such as those discussed in the previous section. Furthermore, countries with a stable and comparatively small HIV prevalence may believe that the HIV 'problem' has been solved. Thus, to better manage current issues and to avert possible future disasters, research is needed on the following topics. How to sustain and strengthen cultures that support and care for the sick and that reduce risk behavior and stigmatization over long periods of time; and how to maintain socio-behavioral conditions that limit HIV spread and the rate at which viral mutation reduces the therapeutic efficacy of medications [9,62]. How to develop cultures of risk-reduction and care in countries or localities where stigma is widespread against marginalized groups and/or people infected with HIV [63]. How to mobilize at-risk populations that have not yet created effective cultures of risk reduction and caring. Potential sources of local or national HIV epidemic outbreaks. We suggest that the following questions should be prioritized since they have received less attention than increases in risk behavior: what social and economic processes shape sexual and injection networks in a locality? As economic development projects can disperse and diffuse networks and communities with high HIV prevalence into localities with low infection rates, and since the normative impacts of such relocations can lead to high-risk behaviors, practices, and networks [11,14], what prevention approaches can either prevent these dislocations or mitigate their effects? (E) Emerging biomedicine Medical advances can generate urgent needs for social research. Such needs can include finding ways to implement new medical possibilities but also ways to cope with any (often unintended) negative social consequences of new discoveries; for example, the impact of antiretroviral therapy on risk-reduction among gay men in some countries [64]. Although it is impossible to forecast biomedical progress, the following issues should become foci of increased research effort. To investigate impacts of introduction of new treatments and concomitant increases in HIV-testing on stigma and discrimination [65]. To determine how medical technologies such as vaccines, microbicides or pre-exposure prophylaxis affect behavioral prevention measures and political and economic support for prevention programs. This is especially important for middle to low efficacy prevention technologies [66–68]. To consider social and cultural impacts of anti-HIV circumcision programs [69–74]. Although recent findings indicate that circumcision lowers the likelihood of HIV infection [69], there is concern that circumcised men who view themselves as 'protected' might engage in more unsafe sex. Adult circumcision might also carry risks, especially if performed by inadequately trained medical personnel or traditional healers. Furthermore, since circumcision is deeply rooted in religious systems and in some countries, such as India, is a mark of racial/ethnic difference, circumcision programs potentially could discredit or weaken HIV prevention and care efforts. To identify socio-cultural, organizational, and political economic barriers which impede vaccination among 'general' and/or oppressed or marginalized populations [75–77]. (F) Possible future widespread failure of previously-effective therapies due to viral evolution or social disorganization Although none of us like to think about it, the race between our ability to devise new medications and the evolutionary mutability of HIV could quite possibly be lost. This could happen because of possible limits to the menu of therapies, the loss of economic or other capacity to develop new therapies (perhaps due to ecologically-generated socio-economic dislocations or a worldwide depression), or socio-cultural disruption due to wars or widespread assumption of power by religious fundamentalisms [78,79]. These circumstances could result in considerable increases in morbidity and mortality in regions of the world where therapy has been accessible to the infected, and could also arouse blaming and stigmatization of the sick. Social research might find solutions to these potential problems before they arise. We suggest that the following issues should be addressed. How to minimize traumatic despair (under different conditions of community resilience and leadership) if therapeutic failure leads to resumed mass morbidity and mortality among the infected. How to maintain or regenerate risk reduction under these conditions. How to prevent political blaming and restriction of medications under these conditions. Obstacles to conducting such research Throughout the epidemic, research funding has been scarce, as have researchers to conduct such research, and high-status journals willing to publish it. In part, this results from long-standing differences between scientific disciplines [80]. Few laboratory scientists have training in social scientific theory or methodologies or in social or behavioral epidemiology. Epidemiologists are more likely to be familiar with social-psychologically oriented behavioral theories, and to have been trained in epidemiologic approaches that treat the individual as the unit of analysis and theorization. However, such training provides little basis for understanding or evaluating social research at higher levels of analysis or using theoretical frameworks that incorporate central concepts such as history, power, and culture. Furthermore, such research can appear to the untrained to have controversial political implications and thus to be 'unscientific' regardless of whether it is based on scientifically valid methods. Questions of what counts as 'appropriate' methods profoundly shape what we know, which affects what social researchers can do and publish in public health [81]. Sociologists, anthropologists, political scientists, and economists often lack training in natural sciences. In many countries, these disciplines emphasize research that develops the social sciences in their own terms – and thus social scientists risk rejection (and reduced career opportunities) if they engage in applied research rather than research on higher-status questions [82]. What do these disjunctures of expertise and interest lead to? Biomedical research funding for HIV, whether provided by governments or pharmaceutical companies, has overwhelmingly concentrated on basic science, clinical research, and epidemiology using the individual as the unit of analysis, and prevention research focusing on behaviors of individuals [83]. Review committees for major funding agencies such as the US National Institutes of Health are almost always comprised of researchers in these specialties. The few social scientists on these committees have usually spent their careers conducting research on behavior change or HIV risk factors at the level of the individual, and thus have difficulty judging proposals on the topics discussed in this article. Editors and reviewers for the major journals in the field, including this one, have similar strengths and weaknesses. Social science funding agencies (which typically disburse much less money) tend to fund research on the 'core problems' of their disciplines (such as social stratification, cultural dynamics, family and interpersonal structures and dynamics, social cohesion, or deviance), rather than applied problems which may be of lower status within the discipline and, arguably, more appropriate for funding by (socially-educated) biomedical agencies. Even such sub-fields as medical sociology and medical anthropology focus on topics such as cultural definitions and beliefs about illness and health; differences in morbidity and mortality by stress level, socio-economic status, gender, or race/ethnicity; and the formal organization and financing of medical services – rather than on social epidemiology, urban health, or questions of prevention or care for infectious diseases. Thus, these issues receive little research funding; and social scientists who study them risk both failing to obtain funding and stigmatization within their professions [84,85]. We have no magic solution. What we do suggest is that the institutions of HIV research, including funders, journals, and academic institutions, acknowledge the seriousness of the problem. The mutual causal interactions between social, political and economic processes and the ever-changing HIV/AIDS epidemic that are discussed in this review are extremely important. They could determine the fates of millions of people and perhaps even the socio-cultural survival of some nations or ethnic groups. We propose that serious discussions be initiated among those funders, journal editors, and social researchers who have engaged with these issues to establish strategies for incorporating social researchers within the structures of the field, and to identify ways that relevant research results can influence by and community-based organizations, and affected A number of and mid-level social factors shape HIV transmission and care by risk networks, behaviors, and the and of sexually transmitted infections and HIV and care. Social processes such as wars and transitions, as as the interactions among emerging rates of disease viral and the social to these, need to be so we can and reduce the that AIDS The relative lack of this of research has the response – both individual and – to the the issues discussed in this paper do not include all of the important social research issues that need to be addressed. important research is at the and individual levels of important social research issues will that as yet be To the extent that and social research, and so social researchers to the field, we will be more likely to identify these issues and conduct the research in time to maximize and minimize The to acknowledge from and The would like to acknowledge support from a number of was by National on projects and to and among and its norms risk in social and for and HIV and by the of Health and was by the Research Social of HIV/AIDS and was by National on norms risk in social support was provided by International and Research HIV

BackgroundSocial networks influence health behavior, including tobacco use and cessation. To date, little is known about whether and how the networks of online smokers and non-smokers may differ, or the potential implications of such differences with regards to intervention efforts. Understanding how social networks vary by smoking status could inform public health efforts to accelerate cessation or slow the adoption of tobacco use.ObjectivesThese secondary analyses explore the structure of ego networks of both smokers and non-smokers collected as part of a randomized control trial conducted within Facebook.MethodsDuring the trial, a total of 14,010 individuals installed a Facebook smoking cessation app: 9,042 smokers who were randomized in the trial, an additional 2,881 smokers who did not meet full eligibility criteria, and 2,087 non-smokers. The ego network for all individuals was constructed out to second-degree connections. Four kinds of networks were constructed: friendship, family, photo, and group networks. From these networks we measured edges, isolates, density, mean betweenness, transitivity, and mean closeness. We also measured diameter, clustering, and modularity without ego and isolates. Logistic regressions were performed with smoking status as the response and network metrics as the primary independent variables and demographics and Facebook utilization metrics as covariates.ResultsThe four networks had different characteristics, indicated by different multicollinearity issues and by logistic regression output. Among Friendship networks, the odds of smoking were higher in networks with lower betweenness (p = 0.00), lower transitivity (p = 0.00), and larger diameter (p = 0.00). Among Family networks, the odds of smoking were higher in networks with more vertices (p = .01), less transitivity (p = .04), and fewer isolates (p = .01). Among Photo networks, none of the network metrics were predictive of smoking status. Among Group networks, the odds of smoking were higher when diameter was smaller (p = .04). Together, these findings suggested that compared to non-smokers, smokers in this sample had less connected, more dispersed Facebook Friendship networks; larger but more fractured Family networks with fewer isolates; more compact Group networks; and Photo networks that were similar in network structure to those of non-smokers.ConclusionsThis study illustrates the importance of examining structural differences in online social networks as a critical component for network-based interventions and lays the foundation for future research that examines the ways that social networks differ based on individual health behavior. Interventions that seek to target the behavior of individuals in the context of their social environment would be well served to understand social network structures of participants.