Small Indirect Effect Research Articles

Longitudinal mediation of processing speed on age-related change in memory and fluid intelligence.

Age-related decline in processing speed has long been considered a key driver of cognitive aging. While the majority of empirical evidence for the processing speed hypothesis has been obtained from analyses of between-person age differences, longitudinal studies provide a direct test of within-person change. Using recent developments in longitudinal mediation analysis, we examine the speed-mediation hypothesis at both the within-and between-person levels in two longitudinal studies, Longitudinal Aging Study Amsterdam (LASA) and Origins of Variance in the Oldest-Old (OCTO-Twin). We found significant within-person indirect effects of change in age, such that increasing age was related to lower speed, which in turn relates to lower performance across repeated measures on other cognitive outcomes. Although between-person indirect effects were also significant in LASA, they were not in OCTO-Twin which is not unexpected given the age homogeneous nature of the OCTO-Twin data. A more in-depth examination through measures of effect size suggests that, for the LASA study, the within-person indirect effects were small and between-person indirect effects were consistently larger. These differing magnitudes of direct and indirect effects across levels demonstrate the importance of separating between- and within-person effects in evaluating theoretical models of age-related change.

An Investigation Into How Students Respond to Being Victimized by Peer Aggression

This study investigates how students respond to peer aggression. Results indicate that boys tend to use more retaliatory responses to peer aggression compared with girls, who are more likely to confide in their friends. The use of humor in response to being victimized also was found to be a promising way to respond to being victimized, especially among boys. Independent of gender, the emotional impact of being victimized was positively associated with reporting to adults at school yet not at home. Furthermore, a small negative indirect effect was found between the emotional impact of being victimized and the likelihood that students would report being victimized to adults at school through the influence of school connectedness. Thus, emotional distress associated with being victimized can erode feelings of being bonded to others at school, further reducing the likelihood that students will report being victimized by peer aggression to adults at school.

Environmental and individual correlates of distress: Testing Karasek's Demand‐Control model in 99 primary care clinical environments

ObjectivesKarasek's job demand‐control model postulates that demand, control, and distress are environmental rather than individual features although these levels are often confounded. The objective was to investigate whether job demand, control, and demand × control predict environmental and individual distress in primary care clinicians, and the mediating role of distress in the relationships between demand and control with intention to leave and absenteeism.DesignPredictive national survey.MethodsWe invited 2,079 staff from 99 general practices in the United Kingdom (843 GPs and nurses, 1,236 administrators) to complete postal questionnaires assessing distress, intention to leave, absenteeism, job demand, and control. Random intercept multilevel models and bootstrapped mediation models were run to test the study hypotheses.ResultsOne thousand five hundred and ninety staff completed questionnaires (77% staff‐level response rate; complete responses by ≥80% of all workers in 68 work environments). There was evidence of environmental variation between practices in intention to leave, absenteeism, job demand, and control, but not distress. Job demand and control both significantly predicted distress, and control moderated the relationship between demand and distress with the effects of demand being reduced at low levels by high control. A small indirect effect via distress was observed for the relationship between job demand and absenteeism, and between job control and intention to leave. No support was found for environmental effects of work settings on distress, but there was evidence of individual‐level effects.ConclusionsThere is a need for considering environmental and individual levels and a danger of generalizing conclusions from one level to the other.Statement of contribution What is already known on this subject? Karasek's job demand‐control model shows consistent prediction of distress in health professionals. Environmental and individual features of distress, demand, and control are often confounded. What does this study add? Nationally representative UK survey of doctors, nurses, and admin primary care staff. Test individual and environment effect of demand and control on distress, absenteeism, leaving intention. Indirect effect of demand on absenteeism via distress and of control on intention to leave via distress.

Subjective Health Complaints and Self-Rated Health: Are Expectancies More Important Than Socioeconomic Status and Workload?

BackgroundThe associations between socioeconomic status (SES), physical and psychosocial workload and health are well documented. According to The Cognitive Activation Theory of Stress (CATS), learned response outcome expectancies (coping, helplessness, and hopelessness) are also important contributors to health. This is in part as independent factors for health, but coping may also function as a buffer against the impact different demands have on health.PurposeThe purpose of this study was to investigate the relative effect of SES (as measured by level of education), physical workload, and response outcome expectancies on subjective health complaints (SHC) and self-rated health, and if response outcome expectancies mediate the effects of education and physical workload on SHC and self-rated health.MethodsA survey was carried out among 1,746 Norwegian municipal employees (mean age 44.2, 81 % females). Structural Equation Models with SHC and self-rated health as outcomes were conducted. Education, physical workload, and response outcome expectancies, were the independent 28 variables in the model.ResultsHelplessness/hopelessness had a stronger direct effect on self-rated health and SHC than education and physical workload, for both men and women. Helplessness/hopelessness fully mediated the effect of physical workload on SHC for men (0.121), and mediated 30 % of a total effect of 0.247 for women. For women, education had a small but significant indirect effect through helplessness/hopelessness on self-rated health (0.040) and SHC (−0.040), but no direct effects were found. For men, there was no effect of education on SHC, and only a direct effect on self-rated health (0.134).ConclusionsThe results indicated that helplessness/hopelessness is more important for SHC and health than well-established measures on SES such as years of education and perceived physical workload in this sample. Helplessness/hopelessness seems to function as a mechanism between physical workload and health.

Does it matter who your schoolmates are? An investigation of the association between school composition, school processes and mathematics achievement in the early years of primary education

Although many studies have focused on the importance of school composition for student achievement, there is still no consensus on whether school composition matters to student achievement, and, if so, why. Therefore, the present study investigates the association between school composition and mathematics achievement at the end of second grade in Flanders. International research points to the initial ability level, SES, ethnicity and sex composition of the school as potential variables in explaining differences in student achievement. Moreover, some researchers suggest that schools ‘react’ to their student body and for that reason we investigated the possible association between school composition and school processes. Data from the SiBO Project have been analyzed using multilevel regression and multilevel mediation analysis. The results showed no direct school composition effects with respect to prior achievement, SES, ethnicity and sex on math achievement. We found two small differential effects, indicating that mean school prior achievement seems to positively affect initially high achievers, and the proportion of minority students in school seems to negatively affect students speaking a non‐European language except for Turkish, Arabic or Berber at home. Furthermore, two small indirect effects were found which suggest that schools with a high mean prior achievement or a high mean SES keep in regular contact with their students' parents and this, in turn, appears to enhance students' math achievement. Overall, our results seem to indicate that school composition in the early years of primary education hardly matters.

Direct and Indirect Effects of Looming Cognitive Style via Social Cognitions on Social Anxiety, Depression, and Hostility

Based on the looming vulnerability model, we hypothesized that mental simulations of scenarios rapidly intensifying and heading in a more threatening direction, as assessed by the looming cognitive style (LCS; Riskind, Williams, Theodore, Chrosniak, & Cortina, 2000), would have effects on social anxiety. Moreover, we expected that these simulations could affect social anxiety through both a direct and an indirect route mediated by verbal social cognitions. Consistent with these hypotheses, structural equations analyses on data from Spanish university and professional students (N = 547) indicated direct and indirect links between looming cognitive style and social anxiety. In addition, similar but smaller effects of looming cognitive style were found on depression symptoms, and a small indirect effect of looming cognitive style was found to be hostility. Together, these findings are consistent with the view that dynamic simulations of patterns of dynamic changes and forward progress of threat play an impor...

Parent beliefs and children's social-behavioral functioning: The mediating role of parent–teacher relationships

This research investigated whether parent–teacher relationship quality mediated the relation between parents' motivational beliefs and children's adaptive functioning and externalizing behaviors. The sample consisted of kindergarten through third-grade children with behavioral concerns (N=206). Parents reported on their motivational beliefs (i.e., role construction and efficacy), and teachers reported on the quality of their relationships with parents and children's adaptive functioning (i.e., social and adaptive skills) and externalizing behaviors. Results indicated that parents' motivational beliefs were related significantly and positively to children's adaptive functioning and negatively to children's externalizing behaviors. Parents' motivational beliefs were also significantly associated with enhanced parent–teacher relationship quality. There was a significant medium-sized indirect effect of parents' motivational beliefs on children's adaptive functioning through parent–teacher relationship quality (k2=.12) and a small indirect effect of parents' motivational beliefs on children's externalizing behaviors (k2=.05). This research suggests that parent–teacher relationship quality may be one mechanism by which the benefits of parents' motivational beliefs are transmitted to children.

Direct and Indirect Ecosystem Effects of Evolutionary Adaptation in the Trinidadian Guppy (Poecilia reticulata)

Ecological and evolutionary processes may interact on the same timescale, but we are just beginning to understand how. Several studies have examined the net effects of adaptive evolution on ecosystem properties. However, we do not know whether these effects are confined to direct interactions or whether they propagate further through indirect ecological pathways. Even less well understood is how the combination of direct and indirect ecological effects of the phenotype promotes or inhibits evolutionary change. We coupled mesocosm experiments and ecosystem modeling to evaluate the ecological effects of local adaptation in Trinidadian guppies (Poecilia reticulata). The experiments show that guppies adapted to life with and without predators alter the ecosystem directly through differences in diet. The ecosystem model reveals that the small total indirect effect of the phenotype observed in the experiments is likely a combination of several large indirect effects that act in opposing directions. The model further suggests that these indirect effects can reverse the direction of selection that direct effects alone exert back on phenotypic variation. We conclude that phenotypic divergence can have major effects deep in the web of indirect ecological interactions and that even small total indirect effects can radically change the dynamics of adaptation.

Cognition, coping, and outcome in Parkinson's disease

Cognitive impairment and depression are common and disabling non-motor symptoms of Parkinson's disease (PD). Previous studies have shown associations between them but the nature of the relationship remains unclear. In chronic illness, problem- or task-oriented coping strategies are associated with better outcome but often require higher level cognitive functioning. The present study investigated, in a sample of patients with PD, the relationships between cognitive function, choice of coping strategies, and a broad index of outcome including depression, anxiety, and health-related quality of life (QoL). It was hypothesized that the coping strategy used could mediate the association between cognition and outcome. 347 participants completed the Coping Inventory for Stressful Situations, the Hospital Anxiety and Depression Scale, the Parkinson's Disease Questionnaire-8, the Unified Parkinson's Disease Rating Scale, and the Addenbrooke's Cognitive Examination-Revised. Structural Equation Modeling was used to test the hypothesized model of cognition, coping, and outcome based on a direct association between cognition and outcome and an indirect association mediated by coping. Overall, poorer cognition predicted less use of task-oriented coping, which predicted worse outcome (a latent variable comprised of higher depression and anxiety and lower QoL). The analyses suggested a small indirect effect of cognition on outcome mediated by coping. The findings suggest that patients who fail to employ task-oriented coping strategies may be at greater risk of depression, anxiety, and poor health-related QoL. Even mild to moderate cognitive impairment may contribute to reduced use of task-oriented coping. Suitably adapted cognitive-behavioral approaches may be useful to enable the use of adaptive coping strategies in such patients.

Are the Direct and Indirect Growth Effects of Remittances Significant?

AbstractDevelopment economists believe that migrant workers’ remittances are an important source of funds for long‐run growth. Therefore, recent studies have investigated the growth effects of remittances but reached different conclusions. In these studies, the rate of growth of output is simply regressed on both remittances and the channels through which remittances affect growth. Thus, no distinction has been made between the indirect and direct growth effects of remittances. Such regressions may give unreliable estimates because the channels may also capture some growth effects of remittances, making the growth effects of remittances insignificant. In this study, we make a distinction between the indirect and direct growth effects of remittances. Our model is estimated with panel data of 40 high remittance recipient countries with the system generalized method of moment. We found that remittances have no direct growth effects but they have small indirect growth effects.

Effect of Provisions on the Valuation of a Company

Provisioning means the evaluation of future costs and losses, the estimation of future liabilities towards one’s surroundings, an increase in equity, as well as the real value of assets. During asset valuation, the reserve balance may cause a reduction of the company's value - net assets. This could be a change of a few percentage points. Non-balance provisions cause a decrease in the value of assets, from which liabilities and reserves will be deducted. The value of the enterprise – through asset evaluation – will be lower by a few percentage points. However, it is supplementary capital (capital protection) which has the greatest importance in the methods a company uses in the valuation of assets. As research indicates, retained earnings and additional capital make up 30 -59% of owners equity. When using the multiplier method, reserves have a small indirect effect on the amount of dividends, net income decrease, etc. – due to the reducing of the financial result and taxes. The mixed method takes up an important position in the valuation of a company’s goodwill. Therefore, the relevance of provisions in this valuation, will be lower than the during the valuation of assets. When valuating income reserves do not play a significant role. They are taken into consideration during the adjustment of the financial result, directing it towards cash flow, and for determining the financial outflows in the form of income tax. Provisions may also have a slight influence on the cost of the capital of the enterprise, i.e. a factor discounting cash flow. Provisions are not cash outflows and therefore, in the most popular income methods, they do not play a significant role. Reserves that are tax-deductible costs may affect the amount of tax burdens and thus indirectly affect the cash flow. The biggest and most direct effect of provisions on the valuation of a company can be observed in the asset methods as well as in the mixed methods. However, in the reserve multiplier methods affect the value of the multiplier element of a listed company and the value of the company measured the base element.

Changes in soil organic carbon, total nitrogen, and abundance of arbuscular mycorrhizal fungi along a large-scale aridity gradient

Abstract Changes in soil organic carbon, total nitrogen, pH, and the abundance of arbuscular mycorrhizal fungi are examined along a large-scale aridity gradient from southeast to northwest in China. Soil organic carbon and total nitrogen decreased but pH increased with increased aridity. Aboveground plant biomass, spore abundance, and colonization of roots by arbuscular mycorrhizal fungi also declined as the aridity increased. Soil organic carbon and total nitrogen were positively correlated with aboveground plant biomass, and arbuscular mycorrhizal fungal spore number and root colonization were positively correlated with soil organic carbon, total nitrogen, and aboveground plant biomass but were negatively correlated with soil pH. A structural equation model suggested that aridity affected soil organic carbon and total nitrogen by limiting aboveground plant biomass. Aridity exerted a large direct effect and smaller indirect effects (via changes in aboveground plant biomass) on the abundance of arbuscular mycorrhizal fungi. Soil pH also directly influenced arbuscular mycorrhizal fungal abundance. These results suggest that aboveground plant biomass could be a key factor driving the changes of soil organic carbon, total nitrogen, and arbuscular mycorrhizal fungal abundance along this aridity gradient in China.

P01-184 - Comparative effects of pregabalin on anxiety and sleep disturbance: Results of a path analysis

IntroductionSleep disturbance is one of the key DSM-IV criteria for generalized anxiety disorder (GAD), and represents the chief complaint in approximately one-third of patients presenting in the primary care setting.Objectives/aimsTo evaluate the extent to which improvement in anxiety is a direct effect of treatment with pregabalin, or is an indirect effect mediated by improvement in sleep disturbance, and vice-versa.MethodsData were pooled from 4 double-blind, placebo-controlled (n = 406) short-term trials of pregabalin (all doses combined; n = 853) in the treatment of generalized anxiety disorder (GAD). The effect of treatment on anxiety was measured using the Hamilton Anxiety Rating Scale (HAM-A), effect of treatment on sleep disturbance was measured using the 3-item Hamilton Depression Rating Scale (HAM-D) sleep factor. Path analyses, using a set of multivariate regression models, were used to evaluate the reciprocal effects of pregabalin on improvement in anxiety in the presence of improvement in sleep disturbance, and vice-versa.ResultsSleep disturbance was common in this GAD sample, with 51.2% (placebo) and 52.2% (pregabalin) of patients, respectively, reporting moderate-to-severe insomnia (HAM-D sleep factor score ≥3). The results of the path analysis indicated that 91.7% (P < 0.0001) of improvement in anxiety was a direct effect of treatment with pregabalin, while 8.3% of improvement in anxiety was an indirect effect, mediated by improvement in sleep disturbance.ConclusionsIn this pooled 4-study data set, the anxiolytic efficacy of pregabalin appears to be primarily a direct effect, with only a small (8.3%) indirect effect, mediated by improvement in sleep disturbance.

Evaluating the Indirect Effect of Infant Weight Velocity on Insulin Resistance in Young Adulthood: A Birth Cohort Study From the Philippines

The authors assessed the relation between infant weight velocity and adult insulin resistance, specifically evaluating whether adult size and body fat distribution mediated the association. Data were from the Cebu Longitudinal Health and Nutrition Survey (Cebu, the Philippines), in which a birth cohort was followed to age 22 years (n=1,409; 1983-2005). Insulin resistance was measured using homeostasis model assessment of insulin resistance (HOMA-IR). Weight velocity (g/month) from 0 to 4 months and from 0 to 24 months was assessed. The authors examined direct and total associations between early growth and adult HOMA-IR in linear regression models and used a nonparametric bootstrapping procedure to test indirect effects through adult body mass index (BMI; weight (kg)/height (m)(2)) and waist circumference. Infant weight velocity was positively associated with adult BMI and waist circumference, which positively predicted HOMA-IR. There were no total or direct effects of immediate postnatal weight velocity (0-4 months) on adult HOMA-IR, although indirect effects through BMI and waist circumference were significant. Weight velocity from 0 to 24 months positively predicted HOMA-IR among males only, while indirect effects were significant in both sexes. In a relatively lean sample of young adults from a population with rising rates of diabetes and cardiovascular disease, the authors found evidence for small indirect effects of infant weight velocity on adult insulin resistance mediated through adult BMI and waist circumference.

A panel data analysis of the growth effects of remittances

Many development economists believe that remittances by the migrant workers are an important source of funds for long run growth. Therefore, recent studies have investigated the growth effects remittances in the recipient countries but reached different conclusions. This paper analyses the strength of these effects with a common data set with alternative specifications and estimation methods. Our results show that the direct growth effects of remittances are insignificant. However, remittances may have small indirect growth effects.

Longitudinal analysis of Plantago: adaptive benefits of iteroparity in a short‐lived, herbaceous perennial

Theory suggests that iteroparity may confer greater fitness than semelparity in situations in which temporal environmental variation is high and unpredictable. Variable age-specific mortality, density dependence, and other factors may also favor iteroparity over semelparity. Here, we empirically test the adaptive benefits of greater numbers of reproductive years in a study of reproductive schedules in an experimental population of a short-lived polycarpic perennial, Plantago lanceolata. A large experimental population was established that included four cohorts with similar genetic structure. Individuals were censused for mortality, size, and reproduction for seven years. Plants experienced variable numbers of reproductive years, but one or two years were most common (approximately 46.7% of the population reproduced only once). The probability of flowering at least once prior to death was determined strongly by extrinsic, environmental or intrinsic but environmentally influenced variables, including early-life size, cohort, and block, but also varied with a number of interactions involving paternal lineage. Maternal effects explained small but significant components of the variance in the number of reproductive years among individuals in each cohort, while paternal effects were significant in only two cohorts. Number of reproductive years contributed significantly to fitness in this system, more so than all other variables tested, although most of the variation in relative fitness may be attributed ultimately to environmental influences. We suggest that the high proportion of each cohort composed of plants reproducing only once may be due to environmental constraints on either growth or size. Such environmental influences, particularly on early life size, may result in small but important indirect effects on fitness.

Are Cleanups a Waste? Housing Market Responses to Brownfield Cleanups

Cleaning up brownfields such as Superfund sites is expected to catalyze neighborhood change in the vicinity. Several previous studies have estimated changes in housing prices associated with Superfund sites, with mixed results. This paper provides new estimates of price effects associated with cleanups of these brownfields and assesses alternative explanations for previous results. Issues such as stigma, sorting and Tiebout bias, and housing supply conditions motivate the analysis. Prominent models of housing market responses to brownfield cleanups (e.g., Greenstone and Gallagher 2008) raise important issues of how timing and location are handled in the research design. This analysis shows the sensitivity of results to alternative specifications using different (and arguably more robust) definitions of neighborhoods and different milestones in the cleanup process. Housing price effects are estimated using first-differenced models with Census data aggregated at the block-group level for all metro areas in the nation (from 1990 to 2000). The remediation treatment variable is defined based on three different phases in Superfund cleanup process, and proximity is defined based on alternative spatial proximity measures. An instrumental variables estimator, where lagged geographic and political factors instrument for Superfund site cleanups is used. The results show substantial policy endogeneity and significant variation across alternative proximity definitions, as expected. The variation in results by cleanup phase offer insights into the timing of market responses to amenity improvements. The initial results show a generally positive causal impact of progress towards cleaning up Superfund sites, although completion of the high-visibility “construction” phase attenuates some of that positive effect. The presence of significant indirect price effects would suggest that Superfund site cleanups can trigger changes in other aspects of the neighborhood – transforming the composition of the housing stock and neighbor mix in the area. Our results point to a small indirect effect of improved environmental quality, indicating that these brownfield cleanups catalyze minimal neighborhood change. Thus, policy endogeneity, timing, and spatial definitions matter greatly to identifying price impacts of brownfield cleanups. Transforming neighborhoods more generally, however, does not appear to play an important role in brownfield redevelopment.

A longitudinal study of self-esteem, cultural identity, and academic success among American Indian adolescents.

Latent growth curve modeling was used to estimate developmental trajectories of self-esteem and cultural identity among American Indian high school students and to explore the relationships of these trajectories to personal resources, problem behaviors, and academic performance at the end of high school. The sample included 1,611 participants from the Voices of Indian Teens project, a 3-year longitudinal study of adolescents from 3 diverse American Indian cultural groups in the western United States. Trajectories of self-esteem were clearly related to academic achievement; cultural identity, in contrast, was largely unrelated, with no direct effects and only very small indirect effects. The relationships between self-esteem and success were mediated by personal resources and problem behaviors.

Parenting practices and problem behavior across three generations: Monitoring, harsh discipline, and drug use in the intergenerational transmission of externalizing behavior.

Using data from grandparents (G1), parents (G2), and children (G3), this study examined continuity in parental monitoring, harsh discipline, and child externalizing behavior across generations, and the contribution of parenting practices and parental drug use to intergenerational continuity in child externalizing behavior. Structural equation and path modeling of prospective, longitudinal data from 808 G2 participants, their G1 parents, and their school-age G3 children (n = 136) showed that parental monitoring and harsh discipline demonstrated continuity from G1 to G2. Externalizing behavior demonstrated continuity from G2 to G3. Continuity in parenting practices did not explain the intergenerational continuity in externalizing behavior. Rather, G2 adolescent externalizing behavior predicted their adult substance use, which was associated with G3 externalizing behavior. A small indirect effect of G1 harsh parenting on G3 was observed. Interparental abuse and socidemographic risk were included as controls but did not explain the intergenerational transmission of externalizing behavior. Results highlight the need for preventive interventions aimed at breaking intergenerational cycles in poor parenting practices. More research is required to identify parental mechanisms influencing the continuity of externalizing behavior across generations.

Gender, reasoning ability, and scholastic achievement: A multilevel mediation analysis

The present study investigated gender differences in scholastic achievement (school grades in sciences and languages) as mediated by reasoning ability in a large sample with a clustered data structure from an educational context. Whereas girls outperformed boys in languages, boys excelled in sciences and reasoning. Multilevel analyses indicated a small indirect effect of gender on school grades mediated by reasoning ability. Gender differences in sciences, but not in languages were largely explained by reasoning ability, but not by factors such as gender ratio in the classroom or mental speed. The predictive power of reasoning ability for languages, but not sciences was larger in classrooms with higher mean reasoning ability. Further, gender differences in languages, but not sciences varied significantly across classrooms. Reasoning ability appears to be important for predicting scholastic achievement in sciences, whereas languages are more affected by gender-related attributes.