Predicting and explaining incident and ongoing depression in U.S. Army National Guard members: a lifecourse perspective

The National Guard is a unique, part-time subset of the U.S. military that has been increasingly deployed during recent conflicts, often has a different set of life circumstances compared to full-time Active Duty servicemembers, and is studied much less frequently than are Active Duty populations. Depression, one of the most common mental disorders among both civilian and military populations in the United States (US), is associated with a range of comorbid mental and physical health conditions. The associations between stressful life events throughout the civilian lifecourse—including during childhood—and adult-onset and persistent depression have been documented in some demographic groups, but have not yet been studied in a National Guard population. Stressful civilian life events may be particularly important in this population, due to frequent transitions between military and civilian employment and engagement among Guard members. We used data from the Ohio Army National Guard Mental Health Initiative to investigate the relationship between two domains of civilian life experiences from across the lifecourse and adult depression: (1) early-life adverse experiences, such as being mistreated during childhood, and (2) more recent stressful experiences outside of deployment, such as financial problems or divorce. First, we estimated the relationships between each of these two domains of exposure and the rates of incident depression across four years using Cox proportional hazards models. We found that male servicemembers who reported at least one out of four traumatic childhood events assessed had a 77% higher rate of incident depression during follow-up compared to those who reported no traumatic childhood events, after adjusting for race and age group (95% CI (confidence interval): 1.33, 2.49). When further adjusting for posttraumatic stress disorder (PTSD) in the time between childhood events and depression, this relationship only slightly attenuated (aHR (adjusted hazard ratio) = 1.71, 95% CI: 1.24, 2.35), suggesting that the relationship between traumatic childhood events and adult depression is not driven by PTSD. Furthermore, when stratified by income level, the association between traumatic childhood events and depression was stronger among men making $40,000 per year or less, with an adjusted hazard ratio of 2.06 (95$40,000 per year (aHR = 1.63, 95% CI: 1.09, 2.45). We also found that men who reported at least one out of nine stressful events assessed in the prior year (a time-varying exposure updated over time) had twice the rate of incident of depression overall compared to men who reported no past-year stressful events (95% CI: 1.52, 2.72), adjusting for race, age group, and past-year PTSD. We observed imprecise associations between these exposures and incident depression among women that should be interpreted with caution due to the small sample size (aHR for one or more childhood events: 0.74, 95% CI: 0.35, 1.61 and aHR for past-year stressors: 1.07, 95% CI: 0.57, 2.01). Our second study departed from traditional epidemiologic null hypothesis testing methods, taking instead a prediction approach to studying incident depression. Supervised machine learning—including methods such as tree classification and random forests—have the flexibility to identify predictors that are not pre-specified, and can be used for hypothesis generation. Among both male and female soldiers, we found that reporting verbal abuse by a parent or guardian during childhood, being of mid-level rank status in the military, recently deploying to a non-conflict area, having been robbed, and having been mistreated were all important predictors of incident depression across five years of follow-up. PTSD and traumatic events in adulthood (including combat-related experiences) as well as having children appeared more important for prediction among men compared to women, while military characteristics (e.g., years of service) as well as hearing about traumatic events happening to others (e.g., learning that a family member was in a serious car accident) appeared more predictive of depression for women compared to men. We also identified subgroups of individuals with certain combinations of predictors who were at high risk of depression onset, such as men with both past-year PTSD and a casualty in their unit during their most recent deployment. Overall, prediction accuracies of our algorithms were moderate to good when cross-validated. Our third study returned the specific focus to our two main exposure domains of interest, childhood traumas and adult civilian stressors, but took a different approach for understanding depression as an outcome. While our first two studies assessed depression as a binary construct, our third study identified latent sub-groups of depression symptom patterns—or trajectories—across follow-up using latent class growth analysis, and estimated the associations between life stressors and membership into these different trajectory groups. For both men and women, a four-group depression model was identified, including a stable, symptom free group (showing essentially no depression symptoms at any point during follow-up) that included about 62% of the overall sample, an increasing depression symptom group including 13% of the sample, a decreasing depression symptom group with 16% of the sample, and a “chronic” depression symptom group representing 9% of the sample (staying essentially steady around 4-5 symptoms throughout follow-up). After controlling for sex, race, and age group, soldiers who reported one or more traumatic childhood events had 3.57 times the odds (95% CI: 2.53, 5.05) of belonging to the chronic depression symptom group compared to the symptom free group. Reporting childhood events was also associated with being in the decreasing and increasing depression symptom trajectory groups compared to the symptom free group (aOR (adjusted odds ratio): 2.33, 95% CI: 1.75, 3.11 for the decreasing symptom group and OR: 1.78, 95% CI: 1.29, 2.45 for the increasing symptom group). When controlling for sex, race, age group, and past-year PTSD, time-varying adult stressors had the largest effect on depression symptoms for the increasing depression symptom group compared to other groups, particularly in the last two years of follow-up (where there was an adjusted difference of 1.02 symptoms at each year, for stressors compared to no stressors). The decreasing depression symptom and symptom free groups saw a negligible difference in symptoms when comparing one or more stressors to no stressors, while about a half of a symptom difference was seen for the chronic depression symptom group, unchanging across the follow-up time. All three studies in this dissertation indicated the importance of considering stressful life events that occur outside of deployment when studying the mental health of National Guard servicemembers. These findings may be particularly relevant given the frequent switch between military and civilian engagement in the National Guard, and the relative neglect of this group within military research. Furthermore, our novel machine learning findings helped to bridge the gap between population-level and individual-level prediction of depression among National Guard members. Although replication studies are needed, the results of this dissertation may help inform potential intervention strategies for depression in order to reduce the overall disease burden of the U.S. Army National Guard

Constraining the Solution to the Last Parsec Problem with Pulsar Timing

The detection of a stochastic gravitational-wave signal from the superposition of many inspiraling supermassive black holes with pulsar timing arrays (PTAs) is likely to occur within the next decade. With this detection will come the opportunity to learn about the processes that drive black-hole-binary systems toward merger through their effects on the gravitational-wave spectrum. We use Bayesian methods to investigate the extent to which effects other than gravitational-wave emission can be distinguished using PTA observations. We show that, even in the absence of a detection, it is possible to place interesting constraints on these dynamical effects for conservative predictions of the population of tightly bound supermassive black-hole binaries. For instance, if we assume a relatively weak signal consistent with a low number of bound binaries and a low black-hole-mass to galaxy-mass correlation, we still find that a non-detection by a simulated array, with a sensitivity that should be reached in practice within a few years, disfavors gravitational-wave-dominated evolution with an odds ratio of $\sim$30:1. Such a finding would suggest either that all existing astrophysical models for the population of tightly bound binaries are overly optimistic, or else that some dynamical effect other than gravitational-wave emission is actually dominating binary evolution even at the relatively high frequencies/small orbital separations probed by PTAs.Comment: 14 pages, 8 figure

Gravitational Wave Tests of General Relativity with the Parameterized Post-Einsteinian Framework

Gravitational wave astronomy has tremendous potential for studying extreme astrophysical phenomena and exploring fundamental physics. The waves produced by binary black hole mergers will provide a pristine environment in which to study strong field, dynamical gravity. Extracting detailed information about these systems requires accurate theoretical models of the gravitational wave signals. If gravity is not described by General Relativity, analyses that are based on waveforms derived from Einstein's field equations could result in parameter biases and a loss of detection efficiency. A new class of "parameterized post-Einsteinian" (ppE) waveforms has been proposed to cover this eventuality. Here we apply the ppE approach to simulated data from a network of advanced ground based interferometers (aLIGO/aVirgo) and from a future spaced based interferometer (LISA). Bayesian inference and model selection are used to investigate parameter biases, and to determine the level at which departures from general relativity can be detected. We find that in some cases the parameter biases from assuming the wrong theory can be severe. We also find that gravitational wave observations will beat the existing bounds on deviations from general relativity derived from the orbital decay of binary pulsars by a large margin across a wide swath of parameter space.Comment: 16 pages, 10 figures. Modified in response to referee comment

New record of Hyachelia tortugae Barnard, 1967, an amphipod epibiont on green turtles Chelonia mydas (LINNAEUS, 1758) from Gorgona island (colombian pacific)

Objetivos: Caracterizar los anfípodos recolectados en lavados esofágicos de la tortuga verde Chelonia mydas (Linnaeus, 1758). Alcance: Incremento de la caracterización de la diversidad de un grupo poco estudiado, pero de gran importancia en ambientes bentónicos, en Colombia. Metodología: Los anfípodos fueron recolectados a partir de lavados esofágicos realizados a 77 juveniles de tortuga verde entre febrero y diciembre 2012 en Isla Gorgona, Pacífico Colombiano. Principales resultados: Se reporta por primera vez para el Pacífico Colombiano el anfípodo Hyachelia tortugae Barnard, 1967, una especie que se encuentra exclusivamente como epibionte de tortugas marinas. Se registraron tres individuos en total de H. tortugae en dos de las tortugas analizadas. Adicionalmente, los anfípodos hipéridos Paralycaea gracilis Claus, 1879, Schizoscelus ornatus Claus, 1879 y Parascelus sp. fueron registrados en los contenidos esofágicos de las tortugas. Conclusiones: Este trabajo resalta la necesidad de implementarestudios sistemáticos que permitan caracterizar la fauna asociada a tortugas marinas en el Pacífico colombiano.Objectives: Characterize the amphipods collected in esophageal lavages of the green turtle Chelonia mydas (Linnaeus, 1758). Scope: Increase the characterization of diversity of a poorly known group, but of great importance in benthic environments, in Colombia. Methodology: Amphipods were collected from esophageal lavages carried out on 77 green turtles between February and December 2012 at Gorgona Island, Colombian Pacific. Main results: We report the occurrence of the amphipod Hyachelia tortugae Barnard, 1967, a species that lives exclusively as an epibiont of sea turtles, for the first time for the Colombian Pacific. Three H. tortugae individuals occurred in two of the analyzed turtles. The hyperiid amphipods Paralycaea gracilis Claus, 1879, Schizoscelus ornatus Claus, 1879, and Parascelus sp. were also collected in the esophageal contents of the turtles. Conclusions: This study highlights that systematic studies should be carried out to characterize the associated fauna in sea turtles in the Colombian Pacific

Reestruturação de um distrito escolar no nível do condado: uma análise crítica do desenvolvimento de políticas e políticas para a descentralização

Policymakers and educational leaders continue to use school district decentralization as a reform effort that attempts to shift power and authority from central office administration to school-level leadership. In 2015, the Nevada Legislature passed legislation to restructure the Clark County School District (CCSD), the state’s largest school district, with the intent of breaking it up into smaller districts but instead evolving to decentralization. In this article, we use case study methods to explore the events leading up to the reorganization of CCSD. We take a critical perspective on Kingdon’s multiple streams framework to analyze the reorganization efforts, focusing specifically on how Nevada’s political context provided a window of opportunity for the reorganization to occur. We also examine the extent to which equitable educational opportunity was a factor in these efforts. Our analysis of the reorganization of CCSD contributes to a wider understanding of state-level policy development and politics within contemporary educational contexts. In this case, we find that state-level policymakers successfully leveraged the opportunity to enact the power and authority necessary to significantly and rapidly impact the structure of one of the largest school districts in the United States.  Los formuladores de póliticas y los líderes educativos continúan con el uso de la descentralización del distrito escolar como un esfuerzo de reforma que intenta cambiar el poder y la autoridad de la administración de la oficina central al liderazgo a nivel escolar. Durante 2015, la Legislatura de Nevada aprobó una ley para reestructurar el Distrito Escolar del Condado de Clark (CCSD), el distrito escolar más grande del estado, con la intención de dividirlo en distritos más pequeños, pero se desarrolló hacia la descentralización. En este artículo, usamos métodos de estudio de caso para explorar los eventos que causaron la reorganización de CCSD. Tomamos una perspectiva crítica sobre el multiple streams framework de Kingdon para analizar los esfuerzos de reorganización, centrándonos específicamente en como el contexto político de Nevada creo oportunidades para que se produzca la reorganización. También examinamos el punto en cual la oportunidad educativa equitativa fue un factor en estos esfuerzos. Nuestro análisis de la reorganización de CCSD contribuye a una comprensión más amplia del desarrollo de la política y las pólizas a nivel estatal dentro de contextos educativos contemporáneos. En este caso, encontramos que los legisladores a nivel estatal exitosamente aprovecharon la oportunidad de representar el poder y la autoridad necesaria para tener un impacto significativo y rápido en la estructura de uno de los distritos escolares más grandes de los Estados Unidos.Os formuladores de políticas e os líderes educacionais continuam a usar a descentralização do distrito escolar como um esforço de reforma que tenta mudar o poder e a autoridade da administração do escritório central para a liderança do nível escolar. Em 2015, o Legislativo de Nevada aprovou uma lei para reestruturar o Distrito Escolar do Condado de Clark (CCSD), o maior distrito escolar do estado, com a intenção de dividi-lo em distritos menores, mas desenvolvido para a descentralização. Neste artigo, utilizamos métodos de estudo de caso para explorar os eventos que causaram a reorganização do CCSD. Nós tomamos uma perspectiva crítica sobre o quadro de múltiplos fluxos de Kingdon para analisar os esforços de reorganização, enfocando especificamente sobre como o contexto político em Nevada cria oportunidades de reorganização. Nós também examinamos o ponto em que a igualdade de oportunidades educacionais foi um fator nesses esforços. Nossa análise da reorganização do CCSD contribui para uma compreensão mais ampla do desenvolvimento de políticas e políticas a nível estadual no contexto educacional contemporâneo. Nesse caso, descobrimos que os legisladores estaduais conquistaram com sucesso a oportunidade de representar o poder e a autoridade necessários para ter um impacto significativo e rápido na estrutura de um dos maiores distritos escolares nos Estados Unidos