The role of social cognitions in the social gradient in adolescent mental health: A longitudinal mediation model

The social gradient in adolescent mental health is well established: adolescents' socioeconomic status is negatively associated with their mental health. However, despite changes in social cognition during adolescence, little is known about whether social cognitions mediate this gradient. Therefore, this study tested this proposed mediational path using three data waves, each 6 months apart, from a socioeconomically diverse sample of 1,429 adolescents (Mage = 17.9) in the Netherlands. Longitudinal modeling examined whether three social cognitions (self-esteem, sense of control, and optimism) mediated associations between perceived family wealth and four indicators of adolescent mental health problems (emotional symptoms, conduct problems, hyperactivity, and peer problems). There was evidence of a social gradient: adolescents with lower perceived family wealth reported more concurrent emotional symptoms and peer problems and an increase in peer problems 6 months later. Results also showed evidence of mediation through social cognitions, specifically sense of control: adolescents with lower perceived family wealth reported a decrease in sense of control (though not self-esteem nor optimism) 6 months later, and lower sense of control predicted increases in emotional symptoms and hyperactivity 6 months later. We found concurrent positive associations between perceived family wealth and all three social cognitions, and concurrent negative associations between social cognitions and mental health problems. The findings indicate that social cognitions, especially sense of control, may be an overlooked mediator of the social gradient in adolescent mental health.

Body image as a mediator in the relationship between psychotic experiences and later disordered eating: A 12-month longitudinal study in high school adolescents

BACKGROUND

The relationship between psychosis and disordered eating remains a challenging area of research to which little interest was paid. Using longitudinal data, we aimed to explore the hypothesis that the pathways from psychotic experiences (PEs) to disordered eating (DE) and body-mass index (BMI) are mediated by body-image disturbances.

METHODS

A prospective longitudinal study was performed. High-school students (N = 510, 61.2% females, mean age of 16.05 ± 1.01 years) were asked to complete three scheduled assessments (Baseline, 6 months, and 12 months).

RESULTS

Two body image components, that is, Overweight Preoccupation and Body Area Satisfaction, mediated the prospective association between baseline PEs and DE 12 months later. Direct effects were significant. After accounting for indirect effects through more severe body image concerns at 6 months, higher baseline PEs were significantly associated with greater DE at 12 months. Baseline PEs and 6-month body image explained a significant proportion of variance in 12-month DE. However, we did not find evidence of a direct prospective association between PEs and BMI.

CONCLUSION

This study is the first to assess the mediating role of body image between PEs and DE. Findings offer promising new avenues for early intervention to help mitigate the effects of PEs on DE in adolescents.

Longitudinal Mediating Effect of Depression on the Relationship between Excessive Daytime Sleepiness and Activities of Daily Living in Parkinson's Disease

OBJECTIVES

Whether depression affects activities of daily living (ADLs) in patients with Parkinson's disease (PD) via excessive daytime sleepiness (EDS) remains unclear; moreover, few longitudinal studies have been conducted.

METHODS

We recruited 421 patients from the Parkinson's Progression Markers Initiative. We constructed a latent growth mediation model to explore the longitudinal mediating effect of depression on the relationship between EDS and ADLs.

RESULTS

EDS (p < .001) and depression scores (p < .001) both increased, and ADL scores (p < .001) decreased. Moreover, EDS was positively correlated with depression, whereas an increase in EDS significantly reduced ADLs. The initial value (95% confidence interval [CI]: 0.026, 0.154) and the rate of change (95% CI: 0.138, 0.514) of self-reported depression measured using the Geriatric Depression Scale(GDS) partially mediated the association between EDS and ADL score.

CONCLUSIONS

The indirect effect of the longitudinal changes of depression on the relationship between EDS and ADLs highlights the importance of depression changes in PD patients with EDS.

CLINICAL IMPLICATIONS

Depression should be considered a mediator by clinicians; preventing the worsening of depression is essential for improving ADLs in patients with PD, especially those with EDS.

Relations among self-control, hope, and psychological adjustment: A two-wave longitudinal mediation study

While the relationships between self-control, hope, and psychological adjustment have been examined in cross-sectional studies, the fact that these variables have not been considered together in any longitudinal research creates a gap in the literature. Therefore, our study aimed to investigate the longitudinal relationships between self-control, hope, and psychological adjustment. Specifically, a cross-lagged panel study in two waves was conducted to examine whether hope mediated the association between self-control and psychological adjustment using a Turkish college sample (N = 349). The results revealed that hope had a significant mediation effect in the longitudinal association between self-control and psychological adjustment. In this direction, self-control indirectly predicts psychological adjustment through hope. This longitudinal study reveals that having self-control may have a positive influence on a person's level of hope and that hope may be a significant predictor of individual psychological adjustment.

Work-family conflicts and pain interference among midlife adults: a longitudinal serial mediation via family strain and loneliness

OBJECTIVE

Work-family conflict has been shown to adversely affect individuals' health and function, particularly among individuals with chronic pain. The current study's longitudinal serial mediation model examined whether work-to-family conflict predicted greater pain interference through higher levels of family strain and loneliness among midlife adults with chronic pain.

METHODS AND MEASURES

The study consisted of 303 participants from two waves of the national longitudinal study of Midlife in the United States (MIDUS) at wave II from 2004 to 2006 (Mage = 57, SD = 11) and wave 3 from 2013 to 2014 (Mage = 66, SD = 11). Participants were employed at time 1 and had chronic pain at both time points, and 54.5% of participants identified as female.

RESULTS

Family strain at time 1 (T1) and loneliness at time 2 (T2), respectively, significantly mediated the association of work-to-family conflict (T1) on pain interference at T2. Participants with greater work-to-family conflict perceived more family strain, felt lonelier, and, in turn, reported experiencing higher interference from chronic pain.

CONCLUSION

Results suggest that unmanaged work-to-family conflict could be a risk factor that exacerbates chronic pain symptoms through worsening family relationships and loneliness among midlife adults with chronic pain.

Depression as a Mediator and Social Participation as a Moderator in the Bidirectional Relationship Between Sleep Disorders and Pain: Dynamic Cohort Study

BACKGROUND

Chronic pain, sleep disorders, and depression are major global health concerns. Recent studies have revealed a strong link between sleep disorders and pain, and each of them is bidirectionally correlated with depressive symptoms, suggesting a complex relationship between these conditions. Social participation has been identified as a potential moderator in this complex relationship, with implications for treatment. However, the complex interplay among sleep disorders, pain, depressive symptoms, and social participation in middle- and old-aged Asians remains unclear.

OBJECTIVE

This study aimed to examine the bidirectional relationship between sleep disorders and pain in middle- and old-aged Chinese and measure the role of depression as a mediator and social participation as a moderator in this bidirectional relationship through a dynamic cohort study.

METHODS

We used data from the China Health and Retirement Longitudinal Study across 5 years and included a total of 7998 middle- and old-aged people (≥45 years old) with complete data in 2011 (T1), 2015 (T2), and 2018 (T3). The cross-lag model was used to assess the interplay among sleep disorders, pain, depressive symptoms, and social participation. Depressive symptoms were assessed by the 10-item Centre for Epidemiological Studies Depression scale. Sleep disorders were assessed by a single-item sleep quality scale and nighttime sleep duration. The pain score was the sum of all pain locations reported. Social participation was measured using self-reported activity.

RESULTS

Our results showed significant cross-lagged effects of previous sleep disorders on subsequent pain at T2 (β=.141; P<.001) and T3 (β=.117; P<.001) and previous pain on subsequent poor sleep at T2 (β=.080; P<.001) and T3 (β=.093; P<.001). The indirect effects of previous sleep disorders on pain through depressive symptoms (β=.020; SE 0.004; P<.001; effect size 21.98%), as well as previous pain on sleep disorders through depressive symptoms (β=.012; SE 0.002; P<.001; effect size 20.69%), were significant across the 3 time intervals. Among participants with high levels of social participation, there were no statistically significant effects of previous sleep disorders on subsequent pain at T2 (β=.048; P=.15) and T3 (β=.085; P=.02), nor were there statistically significant effects of previous pain on subsequent sleep disorders at T2 (β=.037; P=.15) and T3 (β=.039; P=.24). Additionally, the mediating effects of depressive symptoms on the sleep disorders-to-pain pathway (P=.14) and the pain-to-sleep disorders pathway (P=.02) were no longer statistically significant.

CONCLUSIONS

There is a bidirectional relationship between sleep disorders and pain in middle- and old-aged Asians; depression plays a longitudinal mediating role in the bidirectional relationship between them; and social participation moderates the bidirectional relationship between them directly and indirectly by affecting depression. Future interventions may consider the complex relationship between these conditions and adopt a comprehensive treatment regime.

Moderators and mediators of change of an internet-based mindfulness intervention for college students: secondary analysis from a randomized controlled trial

Background

Existing evidence suggests internet- and mobile-based interventions (IMIs) improve depressive symptoms in college students effectively. However, there is far less knowledge about the potential mechanisms of change of mindfulness-based IMIs, which could contribute to optimizing target groups and interventions. Hence, within this secondary analysis of data from a randomized controlled trial (RCT), potential moderators and mediators of the effectiveness of the IMI StudiCare Mindfulness were investigated.

Methods

Moderation and mediation analyses were based on secondary data from a RCT that examined the effectiveness of the 7-module IMI StudiCare Mindfulness in a sample of college students (intervention group: n = 217; waitlist control group: n = 127). Assessments were collected before (t0; baseline), 4 weeks after (t1; during intervention), and 8 weeks after (t2; post-intervention) randomization. Longitudinal mediation analyses using structural equation modeling were employed, with depressive symptom severity as the dependent variable. For moderation analyses, bilinear interaction models were calculated with depressive symptom severity and mindfulness at t2 as dependent variables. All data-analyses were performed on an intention-to-treat basis.

Results

Mediation analyses showed a significant, full mediation of the intervention effect on depressive symptom severity through mindfulness (indirect effect, a*b = 0.153, p < 0.01). Only the number of semesters (interaction: β = 0.24, p = 0.035) was found to moderate the intervention's effectiveness on depressive symptom severity at t2, and only baseline mindfulness (interaction: β = -0.20, p = 0.047) and baseline self-efficacy (interaction: β = -0.27, p = 0.012) were found to be significant moderators of the intervention effect on mindfulness at t2.

Conclusion

Our results suggest a mediating role of mindfulness. Moderation analyses demonstrated that the intervention improved depressive symptom severity and mindfulness independent of most examined baseline characteristics. Future confirmatory trials will need to support these findings.

Clinical Trial Registration

The trial was registered a priori at the WHO International Clinical Trials Registry Platform via the German Clinical Studies Trial Register (TRN: DRKS00014774; registration date: 18 May 2018).

A longitudinal examination of the association between fear of COVID-19, resilience, and mental health during COVID-19 outbreak

The purpose of this study was to examine the impact of fear of COVID-19 on depression and anxiety in longitudinal data and whether this relationship can be mediated by resilience. The sample of the study comprised of 144 university students (77% female and 23% male) between 18 and 39 years of age (M = 22.74 ± 2.93) and participants completed the Fear of COVID-19 Scale (FCV-19S), Brief Resilience Scale (BRS), and Symptom Checklist-90-Revised (SCL-90-R) at Time 1 and Time 2. Mediation analyses demonstrated that resilience (T2) was a significant mediator between fear of COVID-19 (T1) and depression and anxiety (T2). The findings of the study highlight the potential key role of resilience as a protective factor against the negative effects of pandemic challenges on individuals' mental health.

Clarifying the Implicit Assumptions of Two-Wave Mediation Models via the Latent Change Score Specification: An Evaluation of Model Fit Indices

Statistical mediation analysis is used to investigate mechanisms through which a randomized intervention causally affects an outcome variable. Mediation analysis is often carried out in a pretest-posttest control group design because it is a common choice for evaluating experimental manipulations in the behavioral and social sciences. There are four different two-wave (i.e., pretest-posttest) mediation models that can be estimated using either linear regression or a Latent Change Score (LCS) specification in Structural Equation Modeling: Analysis of Covariance, difference and residualized change scores, and a cross-sectional model. Linear regression modeling and the LCS specification of the two-wave mediation models provide identical mediated effect estimates but the two modeling approaches differ in their assumptions of model fit. Linear regression modeling assumes each of the four two-wave mediation models fit the data perfectly whereas the LCS specification allows researchers to evaluate the model constraints implied by the difference score, residualized change score, and cross-sectional models via model fit indices. Therefore, the purpose of this paper is to provide a conceptual and statistical comparison of two-wave mediation models. Models were compared on the assumptions they make about time-lags and cross-lagged effects as well as statistically using both standard measures of model fit (χ2, RMSEA, and CFI) and newly proposed T-size measures of model fit for the two-wave mediation models. Overall, the LCS specification makes clear the assumptions that are often implicitly made when fitting two-wave mediation models with regression. In a Monte Carlo simulation, the standard model fit indices and newly proposed T-size measures of model fit generally correctly identified the best fitting two-wave mediation model.

Activities of daily living as a longitudinal moderator of the effect of autonomic dysfunction on anxiety and depression of Parkinson's patients

BACKGROUND

There is no clear time point for the onset of depression and anxiety in Parkinson's disease (PD), and their atypical physical symptoms often overlap with other nonmotor symptoms. Autonomic dysfunction usually appears earlier than motor symptoms, seriously impairing activities of daily living (ADL), even quality of life. Whether autonomic dysfunction can affect depression and anxiety in PD patients through ADL is still unclear.

METHODS

We conducted three progressive autoregressive mediation models to evaluate whether ADL may mediate the association between autonomic symptom burden, where the mediation chain with autonomic function as an independent variable, ADL as a mediating variable, and anxiety and depression as dependent variables. The ADL of PD patients were measured by the Scales for Outcomes in Parkinson's disease-Autonomic (SCOPA-AUT) and Modified Schwab and England ADL scale, respectively, and the status of depression and anxiety were measured by the Geriatric Depression Scale (GDS) and State-Trait Anxiety Inventory (STAI).

RESULTS

There were 338 PD patients, including 220 males and 118 females. Demographic information, including age, gender, and education level, were not correlated with the depression and anxiety. Model III had the smallest AIC (AIC = 12,669.89), and the cross-lagged relations were not statistically significant, so we selected Model II as the optimal model. In Model II, longitudinal autoregressive mediated effect and longitudinal mediated effect of autonomic dysfunction affecting anxiety and depression through ADL were not statistically significant, suggesting longitudinal changes of autonomic dysfunction were independent of anxiety and depression through ADL. Contemporaneous mediated effects of autonomic dysfunction affecting anxiety and depression through ADL were statistically significant, suggesting contemporaneous autonomic dysfunction may contribute to anxiety and depression through ADL.

CONCLUSIONS

Targeted prevention and intervention measures for autonomic dysfunction and ADL should be taken to preserve and improve self-perceived life satisfaction in the clinical practice and preventive health care of PD.

The mediating role of partner communication on contraceptive use among adolescent girls and young women participating in a small-group intervention in Malawi: A longitudinal analysis

Though effective reproductive health interventions have been developed for adolescent girls and young women (AGYW) in sub-Saharan Africa, few have explored whether specific components of the interventions are responsible for observed changes in behaviour. Data for this longitudinal mediation analysis come from a quasi-experimental, sexual and reproductive health study conducted among AGYW (age 15-24) in Malawi. We assessed the extent to which the relationship between attending communication-specific small-group sessions and contraceptive use at one-year was mediated by contraceptive communication with partners at six months, using a bootstrapping procedure to estimate indirect effects. Of 358 participants, 44% attended communication-specific small-group sessions, 37% communicated with partners about contraception at six months, and 21% used non-barrier contraception at one-year. Participants who attended communication-specific small-group sessions had increased contraceptive communication with partners at six months (aOR = 1.48, 95% CI: 1.07-2.38) and increased non-barrier contraceptive use at one-year (aOR = 3.53, 95% CI: 1.86-6.69). The relationship between attending communication-specific small-group sessions and non-barrier contraceptive use at one-year was partially mediated by contraceptive communication with partners at six months (indirect effect = 0.04, 95% CI: 0.01-0.07). Our results suggest that contraceptive communication with partners is modifiable through interventions and important for AGYW non-barrier contraceptive uptake.

Longitudinal Mediation Analysis Using Natural Effect Models

Mediation analysis is concerned with the decomposition of the total effect of an exposure on an outcome into the indirect effect, through a given mediator, and the remaining direct effect. This is ideally done using longitudinal measurements of the mediator, which capture the mediator process more finely. However, longitudinal measurements pose challenges for mediation analysis, because the mediators and outcomes measured at a given time point can act as confounders for the association between mediators and outcomes at a later time point; these confounders are themselves affected by the prior exposure and outcome. Such posttreatment confounding cannot be dealt with using standard methods (e.g., generalized estimating equations). Analysis is further complicated by the need for so-called cross-world counterfactuals to decompose the total effect. This work addresses these challenges. In particular, we introduce so-called natural effect models, which parameterize the direct and indirect effect of a baseline exposure with respect to a longitudinal mediator and outcome. These can be viewed as a generalization of marginal structural mean models to enable effect decomposition. We introduce inverse probability weighting techniques for fitting these models, adjusting for (measured) time-varying confounding of the mediator-outcome association. Application of this methodology uses data from the Millennium Cohort Study, a longitudinal study of children born in the United Kingdom between September 2000 and January 2002.

Longitudinal Health Consequences of Childhood Adversity: The Mediating Role of Purpose in Life

Early life adversity has long-term detrimental effects on physical health. Although biological, behavioral, and social factors have been explored as intermediate mechanisms, little research has explored psychosocial factors as potential mediators. This study examined whether purpose in life longitudinally mediates the relationship between childhood adversity and two measures of adult health. Data were obtained from 3,871 participants in the Midlife in the United States (MIDUS) study. We tested a longitudinal mediation model from childhood adversity to adult health via purpose in life, controlling for baseline measures of health. Results indicated that childhood adversity is associated with poorer adult health through direct and mediated paths. Childhood adversity may restrict individuals' sense of purpose in life, and reduced purpose in life is subsequently associated with poorer subjective health and increased likelihood of functional limitations. The findings of this study can be used to inform the development of psychosocial and therapeutic intervention programs and services for adults with a history of childhood adversity.

A Viable Alternative When Propensity Scores Fail: Evaluation of Inverse Propensity Weighting and Sequential G-Estimation in a Two-Wave Mediation Model

Two methods from the potential outcomes framework - inverse propensity weighting (IPW) and sequential G-estimation - were evaluated and compared to linear regression for estimating the mediated effect in a two-wave design with a randomized intervention and continuous mediator and outcome. Baseline measures of the mediator and outcome can be considered confounders of the follow-up mediator - outcome relation for which adjustment is necessary to eliminate bias. To adjust for baseline measures of the mediator and outcome, IPW uses stabilized inverse propensity weights whereas sequential G-estimation uses regression adjustment. Theoretical differences between the models are described, and Monte Carlo simulations compared the performance of linear regression; IPW without weight truncation; IPW with weights truncated at the 1st/99th, 5th/95th, and 10th/90th percentiles; and sequential G-estimation. Sequential G-estimation performed similarly to linear regression, but IPW provided a biased estimate of the mediated effect, lower power, lower confidence interval coverage, and higher mean squared error. Simulation results show that IPW failed to fully adjust the follow-up mediator - outcome relation for confounding due to the baseline measures. We then compared the mediated effect estimates using data from a randomized experiment evaluating a steroid prevention program for high school athletes. Implications and future directions are discussed.

Self-Efficacy as a Mechanism Linking Daily Stress to Mental Health in Students: A Three-Wave Cross-Lagged Study

BACKGROUND AND OBJECTIVES

While stress is generally well established to be predictive for different indicators of mental health, little is known about the longitudinal effects of daily life stressors and the role of self-evaluation factors. We tested whether perceived general self-efficacy is a mediator for the association between daily life stressors and psychopathological symptoms as well as subjective well-being.

METHODS

Data derived from 2160 Chinese university students was assessed at three time points with one-year intervals. We used the Brief Daily Stressor Screening, the General Self-Efficacy Scale, the Positive Mental Health Scale, and the Depression Anxiety and Stress Scales. Total, direct, and indirect effects were estimated using 95% bootstrapped confidence intervals and structural equation modeling.

RESULTS

Latent variable mediation analyses showed that daily stressors were associated with increased symptoms of depression, anxiety, and stress and with decreased subjective well-being. All cross-lagged mediational paths via self-efficacy were significant in predicting positive and negative mental health.

CONCLUSIONS

Considering stress of daily life as well as including the two dimensions of mental health may be important for future research and practice. This study provides novel evidence for mediating stress effects by perceived self-efficacy, which should be focused in intervention- and prevention-based approaches.

Cross-Sectional Analysis of Longitudinal Mediation Processes

Statistical mediation analysis can help to identify and explain the mechanisms behind psychological processes. Examining a set of variables for mediation effects is a ubiquitous process in the social sciences literature; however, despite evidence suggesting that cross-sectional data can misrepresent the mediation of longitudinal processes, cross-sectional analyses continue to be used in this manner. Alternative longitudinal mediation models, including those rooted in a structural equation modeling framework (cross-lagged panel, latent growth curve, and latent difference score models) are currently available and may provide a better representation of mediation processes for longitudinal data. The purpose of this paper is twofold: first, we provide a comparison of cross-sectional and longitudinal mediation models; second, we advocate using models to evaluate mediation effects that capture the temporal sequence of the process under study. Two separate empirical examples are presented to illustrate differences in the conclusions drawn from cross-sectional and longitudinal mediation analyses. Findings from these examples yielded substantial differences in interpretations between the cross-sectional and longitudinal mediation models considered here. Based on these observations, researchers should use caution when attempting to use cross-sectional data in place of longitudinal data for mediation analyses.

Pathways from maternal depression to young adult offspring depression: an exploratory longitudinal mediation analysis

Maternal depression in the peri-natal period is associated with increased risk for young adult depression in offspring. This study explored mediation of these links via trajectories of child conduct and emotional problems (Strengths and Difficulties Questionnaire) from ages 4-16 years old in data from the Avon Longitudinal Study of Parents and Children cohort (n = 13373). Through gender-specific structural equation models, a composite measure of exposure to early maternal depression (Edinburgh Postnatal Depression Scale), predicted young adult depression at age 18 (Revised Clinical Interview Schedule - distal outcome). Mediational effects were then estimated by testing which parts of joint piecewise latent trajectory models for child/adolescent conduct and emotional problems were associated with both exposure and distal outcome. For girls, only conduct problems in early childhood were consistently indicated to mediate effects of early maternal depression on risk of young adulthood depression. Some evidence for a pathway via changing levels of childhood and adolescent emotional difficulties was also suggested. For boys, by contrast, the differing models gave less consistent findings providing some evidence for a small time-specific indirect effect via early childhood conduct problems. In addition to its practice implications the current methodological application offers considerable potential in exploratory longitudinal developmental mediation studies. © 2016 The Authors International Journal of Methods in Psychiatric Research Published by John Wiley & Sons Ltd.

Comparing models of change to estimate the mediated effect in the pretest-posttest control group design

Models to assess mediation in the pretest-posttest control group design are understudied in the behavioral sciences even though it is the design of choice for evaluating experimental manipulations. The paper provides analytical comparisons of the four most commonly used models used to estimate the mediated effect in this design: Analysis of Covariance (ANCOVA), difference score, residualized change score, and cross-sectional model. Each of these models are fitted using a Latent Change Score specification and a simulation study assessed bias, Type I error, power, and confidence interval coverage of the four models. All but the ANCOVA model make stringent assumptions about the stability and cross-lagged relations of the mediator and outcome that may not be plausible in real-world applications. When these assumptions do not hold, Type I error and statistical power results suggest that only the ANCOVA model has good performance. The four models are applied to an empirical example.

The role of sleep disturbances in the longitudinal relationship between psychosocial working conditions, measured by work demands and support, and depression

STUDY OBJECTIVES

Because work demands and lack of social support seem to be prospectively linked to sleep problems, and sleep problems are linked to depression, sleep problems may play a role in the relationship between these work characteristics and depressive symptoms. In order to shed more light on this relationship, the current study investigated whether disturbed sleep is a mediator in the longitudinal relationships between work demands, social support, and depression.

DESIGN

Longitudinal cohort study with repeated survey measures on four occasions.

SETTING

Swedish workforce.

PARTICIPANTS

2,017 working participants from the Swedish Longitudinal Occupational Survey of Health in 2006, 2008, 2010, and 2012.

MEASUREMENTS AND RESULTS

Work demands (four items) and social support (six items) were assessed with the Demand Control Questionnaire, disturbed sleep (four items) with the Karolinska Sleep Questionnaire, and depressive symptoms with a brief subscale (six items) from the Symptom Checklist. Autoregressive longitudinal mediation models using structural equation modeling were tested. The work characteristics, and disturbed sleep, were found to be separately associated with depressive symptoms in subsequent waves. However, only demands were found to be longitudinally related to subsequent disturbed sleep. The longitudinal autoregressive models supported a weak mediating role of disturbed sleep in the relationship between demands and depressive symptoms (standardized beta 0.008, P < 0.001), but not between support and depressive symptoms.

CONCLUSIONS

These results indicate that higher demands at work might cause an increase in depressive symptoms, in part, by increasing disturbed sleep, although the mediated effect was relatively small compared to the total effect.

Advances in mediation analysis: a survey and synthesis of new developments

Mediation processes are fundamental to many classic and emerging theoretical paradigms within psychology. Innovative methods continue to be developed to address the diverse needs of researchers studying such indirect effects. This review provides a survey and synthesis of four areas of active methodological research: (a) mediation analysis for longitudinal data, (b) causal inference for indirect effects, (c) mediation analysis for discrete and nonnormal variables, and (d) mediation assessment in multilevel designs. The aim of this review is to aid in the dissemination of developments in these four areas and suggest directions for future research.

Indirect Effects of Child Reports of Teacher-Student Relationship on Achievement

The effect of student-reported teacher-student relationship quality (TSRQ) on academic motivation and achievement was investigated among a sample of 690 academically at risk elementary students (52.8% male). Measures of TSRQ, achievement, and motivation were collected annually for 3 consecutive years, beginning when participants were in grade 2 (24.8%) or grade 3 (74.6%). Child-reported conflict was stable across the 3 years, whereas warmth declined. Boys and African American students reported greater conflict than did girls and Caucasian and Hispanic students. Girls and African American students reported higher warmth than boys and non-African American students. Using path analysis, the authors tested the hypothesis that measures of student motivation in Year 2 mediated the effects of conflict and warmth in Year 1 on reading and math achievement in Year 3. Child-perceived conflict predicted cross-year changes in teacher-rated behavioral engagement, which, in turn, predicted cross-year changes in reading and math achievement. Math competence beliefs also mediated the effect of child- perceived warmth on math achievement. Effects controlled for stability of measures across time, the within-wave association between measures, and baseline measures of IQ and economic adversity. Implications of findings for improving the academic achievement of students at-risk for school failure are discussed.

Accuracy of Estimates and Statistical Power for Testing Meditation in Latent Growth Curve Modeling

The latent growth curve modeling (LGCM) approach has been increasingly utilized to investigate longitudinal mediation. However, little is known about the accuracy of the estimates and statistical power when mediation is evaluated in the LGCM framework. A simulation study was conducted to address these issues under various conditions including sample size, effect size of mediated effect, number of measurement occasions, and R2 of measured variables. In general, the results showed that relatively large samples were needed to accurately estimate the mediated effects and to have adequate statistical power, when testing mediation in the LGCM framework. Guidelines for designing studies to examine longitudinal mediation and ways to improve the accuracy of the estimates and statistical power were discussed.