Moderate alcohol consumption and depressive symptoms: A marginal structural model approach promoting causal inference

Importance: Prevention of depressive symptoms and disorders is a key public health priority but requires an improved understanding of modifiable risk and protective factors. A salient unanswered question in this context is whether the apparent protective effect of alcohol against depression may be causal.Objective: To compare the effects of consistent abstinence, occasional, moderate, and heavy alcohol consumption throughout early-to-middle adulthood on depressive symptoms at age 50.Design: This secondary analysis of the National Longitudinal Survey of Youth (NLSY79) cohort employed a marginal structural model approach in assessing the relationship between alcohol consumption in early-to-middle adulthood (29-37 through 41-49) and depressive symptoms at age 50. Alcohol consumption was based on measurements at 1994, 2002, and 2006, covariates at 1992, 1994, and age 40 (1998-2006), and outcome at age 50 (2008-2016). Setting: The NLSY79 is a nationally representative, population-based cohort study.Participants: 5,667 eligible participants at baseline provided valid data on alcohol consumption, depressive symptoms, and covariates of interest. Exposure: Alcohol consumption was categorised as either abstinence, occasional, moderate, or heavy drinking in 1994, 2002, and 2006.Main Outcome and Measure: Depressive symptoms at age 50 as measured by the Centre for Epidemiological Studies-Depression Scale short form (CES-D-SF).Results: Of the 5,667 eligible participants at baseline, 2,862 [50.50%] were female and the mean age was 30.81 [2.24], with 3,593 participants providing valid outcome data for analysis. Results of linear contrasts from marginal structural models were consistent with a J-shaped relationship, where both consistent occasional (b=-0.84, CI= -1.47, -.11) and consistent moderate (b=-1.08, CI=-1.88, -.20) drinkers had significantly reduced predicted CES-D-SF scores at age 50 compared to consistent abstainers. Consistent heavy drinkers were predicted to have increased depressive symptoms, but this was not statistically significant (b=0.34, CI=-0.62, 1.25). In sex-stratified analyses, results were similar for females and males.Conclusions and Relevance: In this secondary analysis of longitudinal data accounting for time-varying exposure and confounding, consistent low-to-moderate alcohol consumption in early-to-middle adulthood predicted lower depressive symptoms at age 50, compared with those abstaining from alcohol. This work offers preliminary evidence that such protective effects may be causal.

Testing extra-linearity across a psychosis continuum

Background It is unclear whether psychotic experiences (PEs) gradually merge into states of clinical psychosis along a continuum which correspond to a dimensional classification or whether latent classes appear above a certain severity threshold which correspond better to diagnostic categories of psychosis. Methods Annual cross-sectional surveys, 2014–19, among Chinese undergraduates (N = 47,004) measured PEs, depression and etiological risk factors using standardized self-report instruments. We created a psychosis continuum with five levels and tested linear and extra-linear contrasts in associated etiological risk factors, before and after adjustment for depression. We carried out latent class analysis. Results Categorical expression of psychosis, including hallucinations and delusions, nuclear symptoms, and nuclear symptoms and depression were found at severe level 5. Etiological risk factors which impacted linearly across the continuum were more common for depression. Child maltreatment impacted extra-linearly on both psychosis and depression. Family history of psychosis impacted linearly on psychosis; male sex and urban birth impacted extra-linearly and were specific for psychosis. Four latent classes were found, but only at level 5. These corresponded to nuclear schizophrenia symptoms, nuclear schizophrenia and depressive symptoms, severe depression, and an unclassified category with moderate prevalence of PEs. Conclusion Quantitative and qualitative changes in the underlying structure of psychosis were observed at the most severe level along a psychosis continuum, where four latent classes emerged. These corresponded to existing categorical classifications but require confirmation with clinical interview. PEs are non-specific and our findings suggest some are on a continuum with depression, whilst others are on a continuum with non-affective psychosis. Differing patterns of impact from etiological risk factors across the spectrum of psychopathology determine outcome at the most severe level of these continua.

A Welch-type test for comparing K linear contrasts under heteroscedasticity with applications to meta-analysis

A test for comparing linear contrasts with heteroscedasticity, both across components of each contrast and between the contrasts, is developed under assumption of normality. The test is based on the weighted sums of squares. This is an extension of methods for weighted one-way ANOVA developed in Welch (1951) under the null, and in Kulinskaya et al. (2000) [12] underthe alternatives. We provide very accurate approximations to the null distribution and to the distribution under alter natives. The quality of these approximations is studied by simulation. The main application is the I by 2 layout which is widespread in meta-analysis. Our methods allow the homo-geneity of effect sizes across I studies to be tested, without the assumption of equal variances in the treatment and the control groups.

Developmental associations between joint engagement and autistic children’s vocabulary: A cross-lagged panel analysis

Cross-lagged panel analysis was used to examine associations between two joint engagement variables; higher order supported joint engagement and higher order supported joint engagement that co-occurs with caregiver’s follow-in talk (higher order supported joint engagement + follow-in), and expressive and receptive vocabulary in a group of young autistic children ( n = 91) with language delay (mean chronological age = 39 months). Variables were measured twice, 8 months apart. Coefficients for cross-lagged variable pairs were derived from structural equation models. Early higher order supported joint engagement was significantly associated with later expressive and receptive vocabulary ( bs = 0.18 and 0.26, respectively), and early higher order supported joint engagement + follow-in was significantly associated with later expressive and receptive vocabulary ( bs = 0.14 and 0.15, respectively). Associations between early vocabulary and later joint engagement were not significant. Linear contrasts between cross-lagged associations did not show a significantly superior association for any early joint engagement variables and later vocabulary variables. However, our results suggest that higher order supported joint engagement and higher order supported joint engagement + follow-in may be useful initial intervention targets for developmental interventions aimed at promoting autistic children’s language development who are initially language delayed. Lay abstract In this study, we used a cross-lagged panel analysis to examine correlations over time between two types of engagement between children and their parents and children’s later expressive and receptive vocabularies. This kind of design can help researchers understand which early developmental achievements “drive” later developmental achievements. It is important for intervention researchers to know which developmental achievements happen first, so that they can set intervention goals appropriately. The two joint engagement variables we examined were (a) higher order supported joint engagement, which occurs when caregivers influence their child’s play with toys and the child reciprocally responds to the caregiver, but does not manage the interaction by shifting gaze between the toys and the caregiver, and (b) higher order supported joint engagement that co-occurs with caregiver’s follow-in talk (higher order supported joint engagement + follow-in). Follow-in talk occurs when the caregiver talks about objects and events that the child is focused on. Ninety-one autistic children ( n = 91) with language delay (mean chronological age = 39 months) participated, along with their primary caregivers. Each of the four variables was measured twice, 8 months apart. Our statistical procedures showed that early higher order supported joint engagement and early higher order supported joint engagement + follow-in were significantly associated with later expressive and receptive vocabulary. In contrast, associations between early vocabulary variables and later joint engagement variables were not significant. Our results suggest that higher order supported joint engagement and higher order supported joint engagement + follow-in may be useful initial intervention targets, for developmental interventions aimed at promoting language development in autistic children who are initially language delayed.

ExploreModelMatrix: Interactive exploration for improved understanding of design matrices and linear models in R

Linear and generalized linear models are used extensively in many scientific fields, to model observed data and as the basis for hypothesis tests. The use of such models requires specification of a design matrix, and subsequent formulation of contrasts representing scientific hypotheses of interest. Proper execution of these steps requires a thorough understanding of the meaning of the individual coefficients, and is a frequent source of uncertainty for end users. Here, we present an R/Bioconductor package, ExploreModelMatrix, which enables interactive exploration of design matrices and linear model diagnostics. Given a sample data table and a desired design formula, the package displays how the model coefficients are combined to give the fitted values for each combination of predictor variables, which allows users to both extract the interpretation of each individual coefficient, and formulate desired linear contrasts. In addition, the interactive interface displays informative characteristics for the regular linear model corresponding to the provided design, such as variance inflation factors and the pseudoinverse of the design matrix. We envision the package and the built-in collection of common types of linear model designs to be useful for teaching and self-learning purposes, as well as for assisting more experienced users in the interpretation of complex model designs.

A Vegetarian-Style Dietary Pattern Is Associated with Lower Energy, Saturated Fat, and Sodium Intakes; and Higher Whole Grains, Legumes, Nuts, and Soy Intakes by Adults: National Health and Nutrition Examination Surveys 2013–2016

Consumer demand for plant-based foods is increasing though the reasons may vary. Plant foods are sole sources of dietary fiber, vitamin C, and flavonoids and good sources of vitamin B1, folic acid, potassium, and magnesium. They are low in saturated fat, and do not contain cholesterol and vitamin B12. Plant foods are associated with better body weight and healthy blood lipid profile. This cross-sectional study used nationally representative National Health and Nutrition Examination Survey 2013–2016 data and compared nutrient and food pattern food group intakes of adults eating a vegetarian-style diet with adults eating a nonvegetarian diet. Adults 20+ years (N = 10,064) were grouped using the Dietary Guidelines for Americans 2015–2020 definition of vegetarian-style diet, which is modelled as lacto-ovo-vegetarian diet. Trained dietary interviewers collected self-reported dietary intake data using a 24-h recall and an automated multi-pass method. Means were compared using linear contrasts (p < 0.01). On average, the vegetarians ate an estimated 419 fewer kilocalories, 7 g less saturated fat, and 1274 mg less sodium. The vegetarian-style diet was higher in micronutrient density, except for vitamin B12 and zinc. The vegetarians ate more whole grains, legumes, nuts, and soy products. Fruit, vegetables, and dairy intakes were similar for both groups. A vegetarian-style diet may be advocated to control energy, saturated fat, and sodium intakes.

ExploreModelMatrix: Interactive exploration for improved understanding of design matrices and linear models in R

Linear and generalized linear models are used extensively in many scientific fields, to model observed data and as the basis for hypothesis tests. The use of such models requires specification of a design matrix, and subsequent formulation of contrasts representing scientific hypotheses of interest. Proper execution of these steps requires a thorough understanding of the meaning of the individual coefficients, and is a frequent source of uncertainty for end users. Here, we present an R/Bioconductor package, ExploreModelMatrix, which enables interactive exploration of design matrices and linear model diagnostics. Given a sample annotation table and a desired design formula, the package displays how the model coefficients are combined to give the fitted values for each combination of predictor variables, which allows users to both extract the interpretation of each individual coefficient, and formulate desired linear contrasts. In addition, the interactive interface displays informative characteristics for the regular linear model corresponding to the provided design, such as variance inflation factors and the pseudoinverse of the design matrix.

Mineral Soil Chemical Properties as Influenced by Long-Term Use of Prescribed Fire with Differing Frequencies in a Southeastern Coastal Plain Pine Forest

Recent studies suggest increased fire frequency may impair soil chemistry, but few studies have examined long-term effects of repeated, frequent prescribed fires on forest soil properties in the southeastern Coastal Plain, USA. In this study, forest soil chemistry at the 0–10 and 10–20 cm mineral soil depths of sandy surface horizons (Entisols and Spodosols) were compared among units burned 0, 4, 6, and 8 times between 2004 and 2015 and 0 and 20 times between 1978 and 2015 in a longleaf (Pinus palustris Mill.)–loblolly (Pinus taeda L.) pine savanna at the Tom Yawkey Wildlife Center (Georgetown, SC, USA). At the 0–10 cm soil depth, soil pH (p = 0.00), sulfur (p = 0.01), calcium (p = 0.01), iron (p < 0.01), manganese (p < 0.01), and aluminum (p = 0.02) treatment means differed (2004–2015). Calcium and manganese displayed positive, significant relationships and sulfur displayed a negative, significant relationship with increasing fire frequency (p < 0.05). However, correlation of these relationships was low (r2 ≤ 0.23). Using linear contrasts to compare the mean of all fire treatments (20 fires from 1978 to 2015) to the mean of the unburned compartment, sulfur (p = 0.01) and iron (p < 0.01) were less in soils from the burned compartments. At the 10–20 cm soil depth, soil pH (p = 0.01), manganese (p = 0.04), phosphorus (p = 0.01), potassium (p = 0.02), and iron (p < 0.01) treatment means differed (2004–2015). Potassium displayed a negative, significant relationship and soil pH displayed a positive, significant relationship with increasing fire frequency (p < 0.05). Correlation of these relationships was low (r2 ≤ 0.16), however. Using linear contrasts to compare the mean of all fire treatments (20 fires from 1978 to 2015) to the unburned compartment, potassium (p = 0.00) and iron (p < 0.01) were less in soils from burned compartments. These results are inconsistent with studies suggesting that forest soil chemistry is substantially altered by increased fire frequency and support other studies from this region that have documented minimal or temporary soil chemical changes associated with frequent prescribed fires.