Shu Xu

Clinical Associate Professor of Biostatistics

Professional overview

Dr. Shu Xu’s work represents a balance of both statistical and applied aspects of quantitative methodology. Her primary quantitative interests include evaluating and developing statistical methods for longitudinal data analysis. Specifically, Dr. Xu’s research focuses on various aspects of latent growth models, missing data methods, and causal inference models.

Dr. Xu has collaborated with substance use, family, and health researchers to advance and share her knowledge of quantitative methodology and pursue a better understanding of the social sciences and public health. She has conducted research with the Family Translational Research Group at NYU and the Methodology Center at the Pennsylvania State University.

Education

BS, Psychology, East China Normal University, Shanghai, China

MS, Quantitative Psychology, University of California, Davis

PhD, Quantitative Psychology, University of California, Davis

Areas of research and study

Biostatistics

Family research

Longitudinal Data Analysis

Missing Data Methods

Mixture Models

Quantitative Research

Publications

Publications

Native Hawaiian and Other Pacific Islanders: Disparities in the Prevalence of Multiple Chronic Conditions

Role of social-cognitive factors in the relationship between e-cigarette use and subsequent cigarette smoking among U.S. youth: A causal mediation analysis

Xu, S., Coffman, D. L., Luta, G., Mai, A., Jiang, N., & Niaura, R. S. (n.d.).

Publication year

2025

Journal title

Addictive Behaviors

Volume

161

10.1016/j.addbeh.2024.108204

Abstract

Abstract

Objective: E-cigarette use is associated with subsequent cigarette smoking among youth. The current study examined the mediating role of social-cognitive factors in this association. Methods: Data from four waves of the Population Assessment of Tobacco and Health study (2013/4 – 2017/8) were analyzed. Among youth who had heard about e-cigarettes at Wave 1 but never used cigarettes before Wave 2, we conducted both causal and traditional mediation analyses to examine the mediated effect of social-cognitive factors (including relative harm perception of e-cigarettes versus cigarettes, harm perception of e-cigarette use, perceptions of addictiveness of e-cigarette use, and e-cigarette use among best friends) in the association between e-cigarette use and subsequent cigarette ever or current smoking, adjusting for covariates. We included sampling weights in all analyses; hence, results are generalizable to the U.S. youth (12 – 14 years) from the 2013–2014 cohort. Results: Results from causal mediation analyses indicated that the total effect of e-cigarette use, compared to no use, increased the risk of cigarette ever smoking (20.9 %) and current smoking (4.6 %). A portion of this effect (4.2 % − 15.1 % for ever smoking; less than 10.6 % for current smoking) can be attributed to changes in social-cognitive factors induced by e-cigarette use. However, these mediated effects were small in magnitude relative to their standard errors and not statistically significant. Results from the traditional mediation analyses largely aligned with these findings, except for a few small sized pathways. Conclusions: For the U.S. youth population, social-cognitive factors may only minimally or not at all mediate the association between e-cigarette use and subsequent cigarette smoking. Further investigation into the mediation role of social-cognitive factors is warranted. Tobacco control interventions that focus on cigarette smoking initiation among youth should target other mediating factors.

Longitudinal association between e-cigarette use and respiratory symptoms among US adults: Findings from the Population Assessment of Tobacco and Health Study Waves 4–5

Prevalence and risk factors of PTSD symptoms: a 3-month follow-up study

The impact of the 2014 military conflict in the east of Ukraine and the Autonomous Republic of the Crimea among patients receiving opioid agonist therapies

Association of Racial Discrimination With Adiposity in Children and Adolescents

Examining the effects of cumulative environmental stressors on Gulf Coast child and adolescent health

Meltzer, G. Y., Merdjanoff, A. A., Xu, S., Gershon, R., Emrich, C. T., & Abramson, D. M. (n.d.).

Publication year

2023

Journal title

Population and Environment

Volume

45

Issue

3

10.1007/s11111-023-00436-1

Abstract

Abstract

This study examines how community-level cumulative environmental stress affects child and adolescent emotional distress and chronic health conditions both directly and indirectly through stressors at the household, family, and individual levels. Data comes from the Women and their Children’s Health (WaTCH) Study, which sought to understand the health implications of exposure to the 2010 Deepwater Horizon oil spill (DHOS) among a cohort of 596 mothers with children ages 10 to 17 in southeastern Louisiana. Community-level environmental stress was measured using a newly developed geospatial index. Household-level stressors included previous hurricane impacts, impacts of DHOS, degree of financial difficulty, and degree of housing physical decay. Family stressors included maternal depression, self-rated physical health, and degree of parenting stress. Child stress was based on perceived stress; child mental health was based on serious emotional disturbance; and child physical health was based on diagnosis of chronic illness. Structural equation modeling used weighted least squares means and variance and theta parameterization. Results showed a significant negative direct path between community-level cumulative environmental stress and child/adolescent serious emotional disturbance and chronic illness. However, the indirect relationship through household, family, and individual-level stressors was significant and positive for both child/adolescent serious emotional disturbance and chronic illness. These findings point to the centrality of the household and family in determining child and adolescent physical and mental health outcomes in communities exposed to frequent disasters and ongoing environmental stressors.

Predictors of Crosscutting Patterns of Psychological Health and Family Maltreatment

Tutorial on Causal Mediation Analysis With Binary Variables: An Application to Health Psychology Research

Xu, S., Coffman, D. L., Luta, G., & Niaura, R. S. (n.d.).

Publication year

2023

Journal title

Health Psychology

Volume

42

Issue

11

Page(s)

778-787

10.1037/hea0001299

Abstract

Abstract

Mediation analysis has been widely applied to explain why and assess the extent to which an exposure or treatment has an impact on the outcome in health psychology studies. Identifying a mediator or assessing the impact of a mediator has been the focus of many scientific investigations. This tutorial aims to introduce causal mediation analysis with binary exposure, mediator, and outcome variables, with a focus on the resampling and weighting methods, under the potential outcomes framework for estimating natural direct and indirect effects. We emphasize the importance of the temporal order of the study variables and the elimination of confounding. We define the causal effects in a hypothesized causal mediation chain in the context of one exposure, one mediator, and one outcome variable, all of which are binary variables. Two commonly used and actively maintained R packages, mediation and medflex, were used to analyze a motivating example. R code examples for implementing these methods are provided.

Use of electronic nicotine delivery system (ENDS) devices among U.S. Youth and adults: Findings from the Population Assessment of Tobacco and Health Study Waves 1–5

Jiang, N., Xu, S., Li, L., Cleland, C. M., & Niaura, R. S. (n.d.).

Publication year

2023

Journal title

Addictive Behaviors

Volume

139

10.1016/j.addbeh.2022.107588

Abstract

Abstract

Introduction: Electronic nicotine delivery system (ENDS) devices evolve rapidly and impact nicotine dependence. This study described the type of ENDS devices used most frequently by U.S. youth and adults from 2013/14 to 2018/19. Methods: We analyzed Waves 1–5 data of the Population Assessment of Tobacco and Health Study. Among current ENDS users, descriptive statistics summarized the most frequently used ENDS devices (i.e., disposable cigalike, refillable cartridge, nonrefillable cartridge, tank, mod, prefilled pod, disposable pod) among youth (12–17 years), young adults (18–34 years), and older adults (≥35 years) for each wave. Results: The proportion of current ENDS users who reported they most frequently used disposable cigalikes and cartridge-based devices declined over time across all age groups. At Waves 1–4, tank was generally the most popular type for all ages and an increasing proportion of ENDS users reported they most frequently used tanks. The primary use of mods decreased among youth, and fluctuated among young and older adults. At Wave 5, prefilled pods became the dominant type (youth: 55.0%; young adults: 44.7%; older adults: 42.7%), and 4.2–10.0% of ENDS users reported using disposable pods most often. The popularity of tanks, mods, and prefilled pods was more evident in youth and young adults, and primary use of disposable pods was more common in older adults. Conclusions: The primary use of ENDS devices changed over the years and varied by age. More research is warranted to continuously monitor the characteristics of ENDS devices in youth and adults to inform product regulations and intervention efforts.

Cigar Use Progression Among New Cigar Initiators: A Two-Part Growth Curve Analysis Among a Youth and Young Adult Cohort

Passive exposure to e-cigarette emissions is associated with worsened mental health

Recurrent Injecting Drug Use as a Mediator between Psychiatric Disorder and Non-Fatal Overdose

Relationships Between E-cigarette Use and Subsequent Cigarette Initiation Among Adolescents in the PATH Study: an Entropy Balancing Propensity Score Analysis

Xu, S., Coffman, D. L., Liu, B., Xu, Y., He, J., & Niaura, R. S. (n.d.).

Publication year

2022

Journal title

Prevention Science

Volume

23

Issue

4

Page(s)

608-617

10.1007/s11121-021-01326-4

Abstract

Abstract

This study aimed to examine the relationship between electronic cigarette use and subsequent combustible cigarette use, controlling for confounding by using a propensity score method approach. Data from the first three annual waves of the Population Assessment of Tobacco and Health study were analyzed (n = 6309). Participants were tobacco-naïve at Wave 1; used e-cigarettes exclusively (n = 414), used combustible cigarettes exclusively (n = 46), or not used any tobacco products (n = 5849) at Wave 2. We conducted entropy balancing propensity score analysis to examine the association between exclusive e-cigarette or cigarette initiation and subsequent cigarette use at Wave 3, adjusting for non-response bias, sampling bias, and confounding. Among tobacco-naïve youth, exclusive e-cigarette use was associated with greater risk for subsequent combustible cigarette smoking initiation (OR = 3.42, 95% CI = (1.99, 5.93)) and past 30-day combustible cigarette use (OR = 2.88, 95% CI = (1.22, 6.86)) in the following year. However, the latter risk was comparatively lower than the risk if youth started with a combustible cigarette (OR = 25.79, 95% CI = (9.68, 68.72)). Results of sensitivity analyses indicated that estimated effects were robust to unmeasured confounding. Use of e-cigarettes in tobacco-naïve youth is associated with increased risk of subsequent past 30-day combustible cigarette use but the risk is an order of magnitude higher if they start with a combustible cigarette.

The Mediating Effect of E-Cigarette Harm Perception in the Relationship between E-Cigarette Advertising Exposure and E-Cigarette Use

Youth E-Cigarette Use and Functionally Important Respiratory Symptoms: The Population Assessment of Tobacco and Health (PATH) Study Waves 3 and 4

Stevens, E. R., Xu, S., Niaura, R., Cleland, C. M., Sherman, S. E., Mai, A., Karey, E., & Jiang, N. (n.d.).

Publication year

2022

Journal title

International journal of environmental research and public health

Volume

19

Issue

22

10.3390/ijerph192215324

Abstract

Abstract

Respiratory effects of e-cigarette use among youth are not fully understood. This study investigated the longitudinal association between e-cigarette use and a validated index of functionally important respiratory symptoms among US youth. Data from Waves 3–4 of the Population Assessment of Tobacco and Health Study were analyzed. The sample included youth (aged 12–17) without asthma at baseline (Wave 3), who completed a follow-up survey (Wave 4), and were not missing data for analytic variables (n = 3899). Exposure was e-cigarette use status (never, former, or current) at baseline. The outcome was a respiratory symptom index based on responses for seven wheezing items at Wave 4. An index of ≥2 was defined as having functionally important respiratory symptoms. Lagged logistic regression models examined the association between baseline e-cigarette use and functionally important respiratory symptoms at follow-up by combustible tobacco use status (never or ever), and controlling for baseline covariates. At baseline, 13.7% of participants reported former e-cigarette use, and 4.3% reported current use. Baseline e-cigarette use did not increase the odds of having functionally important respiratory symptoms at follow-up regardless of combustible tobacco use status. Future research on larger populations of e-cigarette users with longer follow-up periods will improve our understanding of the respiratory risks associated with e-cigarette use among youth.

Cannabis Use and the Onset of Cigarette and E-cigarette Use: A Prospective, Longitudinal Study among Youth in the United States

E-cigarette use, systemic inflammation, and depression

Self-report measures of coercive process in couple and parent–child dyads.

High Sensitivity and Specificity Screening for Clinically Significant Intimate Partner Violence

Psychology of wearing face masks to prevent transition of COVID-19

The lump-versus-split dilemma in couple observational coding: A multisite analysis of rapid marital interaction coding system data.

Using Security Questions to Link Participants in Longitudinal Data Collection

A Randomized, Controlled Trial of the Impact of the Couple CARE for Parents of Newborns Program on the Prevention of Intimate Partner Violence and Relationship Problems

Patterns of psychological health problems and family maltreatment among United States Air Force members