Results indicate that VetChange is effective in reducing drinking and PTSD symptoms in OIF/OEF veterans. Further studies of VetChange are needed to assess web-based recruitment and retention methods and to determine VetChange's effectiveness in demographic and clinical sub-populations of returning veterans.

Mediation analysis has become one of the most popular statistical methods in the social sciences. However, many currently available effect size measures for mediation have limitations that restrict their use to specific mediation models. In this article, we develop a measure of effect size that addresses these limitations. We show how modification of a currently existing effect size measure results in a novel effect size measure with many desirable properties. We also derive an expression for the bias of the sample estimator for the proposed effect size measure and propose an adjusted version of the estimator. We present a Monte Carlo simulation study conducted to examine the finite sampling properties of the adjusted and unadjusted estimators, which shows that the adjusted estimator is effective at recovering the true value it estimates. Finally, we demonstrate the use of the effect size measure with an empirical example. We provide freely available software so that researchers can immediately implement the methods we discuss. Our developments here extend the existing literature on effect sizes and mediation by developing a potentially useful method of communicating the magnitude of mediation.

Emerging methodological research suggests that the World Wide Web (“Web”) is an appropriate venue for survey data collection, and a promising area for delivering behavioral intervention. However, the use of the Web for research raises concerns regarding sample validity, particularly when the Web is used for recruitment and enrollment. The purpose of this paper is to describe the challenges experienced in two different Web-based studies in which participant misrepresentation threatened sample validity: a survey study and an online intervention study. The lessons learned from these experiences generated three types of strategies researchers can use to reduce the likelihood of participant misrepresentation for eligibility in Web-based research. Examples of procedural/design strategies, technical/software strategies and data analytic strategies are provided along with the methodological strengths and limitations of specific strategies. The discussion includes a series of considerations to guide researchers in the selection of strategies that may be most appropriate given the aims, resources and target population of their studies.

The Diagnostic and Statistical Manual-5 (DSM-5) reformulated Posttraumatic Stress Disorder (PTSD) based partially on research showing there were four main factors that underlie the symptoms of the disorder. The primary aim of this study was to examine the temporal stability of the DSM-5 factors as measured by the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5; Weathers et al., 2010). Confirmatory factor analyses were conducted to examine the structure of DSM-5 PTSD, and temporal stability over three time points was examined to determine if the measure reflects a consistent construct over time. Our sample was 507 combat-exposed veterans of Iraq and Afghanistan who enrolled in an online intervention for problem drinking and combat-related stress (masked for review). We administered the PCL-5 at baseline, 8-week post intervention, and 3-month follow-up assessments. The DSM-5 model provided an adequate fit to the data at baseline. Tests of equality of form and equality of factor loadings demonstrated stability of the factor structure over time, indicating temporal stability. This study confirms the results of previous research supporting the DSM-5 model of PTSD symptoms (Elhai et al., 2012; Miller et al., 2012). This is the first study to demonstrate the temporal stability of the PCL-5, indicating its use in longitudinal studies will measure the same construct over time.

The goal of many studies is to identify and understand the processes through which phenomena occur. This goal is often accomplished by studying the effects of an intervening variable, for example, a variable that transmits the effects of an independent variable to a dependent variable. Investigating the nature of intervening variables, or mediators, is commonly known as mediation analysis.When data are clustered within groups, the independence assumption of ordinary least squares (OLS) regression underlying conventional mediation analysis is violated, leading to potentially biased confidence intervals (CIs). A common example of clustering, or nesting, arises in group processes research where individuals are nested within teams (e.g., Nohe, Michaelis,

Objectives To describe characteristics of participants who chose moderation and abstinence drinking goals, and to examine post-treatment drinking outcomes based on patterns of goal choice during a Web-based alcohol intervention for returning U.S. Veterans. Method We conducted a descriptive secondary analysis of a subsample of 305 of 600 Veterans who participated in a clinical trial of VetChange, an 8-module, cognitive-behavioral intervention. Participants self-selected abstinence or moderation drinking goals, initially at Module 3, and weekly during subsequent modules. Alcohol use and alcohol-related problems were measured using the Alcohol Use Disorders Identification Test (AUDIT), Quick Drink Screen (QDS), and Short Inventory of Problems (SIP-2R). Results Initial goal choices were 86.9% moderation and 13.1% abstinence. Approximately 20% of participants from each initial choice changed goals during the intervention; last goal choices were 68.6% moderation and 31.4% abstinence. Participants who initially chose moderation reported higher percent heavy drinking days at baseline; participants who initially chose abstinence were more likely to report recent substance abuse treatment and were older. Post-intervention levels of alcohol use and alcohol-related problems were significantly reduced in all goal-choice patterns (i.e., Moderation Only, Abstinence Only, Moderation to Abstinence, and Abstinence to Moderation; all measures p < 0.05 or less). Baseline drinking severity did not differentially relate to outcomes across goal-choice patterns. Conclusions Participants in a Web-based alcohol intervention for returning U.S. Veterans demonstrated improvements in drinking regardless of whether they chose an abstinence or moderation drinking goal, and whether the goal was maintained or changed over the course of the intervention.

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