Controlling for Unobserved Confounds in Classification Using Correlational Constraints

As statistical classifiers become integrated into real-world applications, it is important to consider not only their accuracy but also their robustness to changes in the data distribution. In this paper, we consider the case where there is an unobserved confounding variable $z$ that influences both the features $\mathbf{x}$ and the class variable $y$. When the influence of $z$ changes from training to testing data, we find that the classifier accuracy can degrade rapidly. In our approach, we assume that we can predict the value of $z$ at training time with some error. The prediction for $z$ is then fed to Pearl's back-door adjustment to build our model. Because of the attenuation bias caused by measurement error in $z$, standard approaches to controlling for $z$ are ineffective. In response, we propose a method to properly control for the influence of $z$ by first estimating its relationship with the class variable $y$, then updating predictions for $z$ to match that estimated relationship. By adjusting the influence of $z$, we show that we can build a model that exceeds competing baselines on accuracy as well as on robustness over a range of confounding relationships.Comment: 9 page

Gender discrimination in hiring across occupations: a nationally-representative vignette study

We investigate gender discrimination in a nationally-representative sample of German firms using a factorial survey design. Short CVs of fictitious applicants for apprenticeship positions are presented to human resource managers who are asked to evaluate the applicants. Women are evaluated worse than men on average, controlling for all attributes of the CV. This measure of discrimination is robust to differences in the variance of unobservable productivity characteristics ("Heckman critique"). Discrimination against women varies across industries and occupations. Controlling for all occupation- and firm-related variables that we observe, only the share of women in an occupation correlates with discrimination

How do childhood ADHD and stress relate to adult wellbeing and educational attainment? A data science investigation using the 1970 British Cohort Study

Background: Attention Deficit Hyperactivity Disorder (ADHD) is a childhood and adult disorder characterised by nonnormative inattentive, impulsive, and hyperactive behaviour. Over time the condition has become increasingly medicalised, and whilst it is estimated to affect 5-7% of schoolchildren internationally (Sayal et al., 2018), only 1.6% are diagnosed with ADHD in the UK (NHS Digital, 2018). Reviews report that childhood ADHD leads to poor adult outcomes in all areas of life (e.g. Costello & Maughan, 2015; Erskine et al., 2016). Although about 50% of ADHD children function well as adults, knowledge is limited about psychosocial factors in outcomes, (Costello & Maughan, 2015) such as those related to stress. State regulation theory, (Sanders, 1983; Sergeant, 2000) was the basis for an investigation using data from the age 0, 5, 10, 34, and 42 sweeps of the 1970 British Cohort Study (BCS70; Centre for Longitudinal Studies: UCL/IoE, 2019). Stress and protective factors were operationalised as stressful life events, chronic stressors, self-esteem, and locus of control. The following questions were examined : 1) What robust measures of DSM-5 ADHD can be retrospectively measured and validated? 2) What is the relationship between childhood ADHD and stress? 3) What is the effect of childhood ADHD on adult a) subjective wellbeing, and b) educational attainment, the latter as a proxy for SES and objective wellbeing? Method: Innovative data science methods were applied, including: 1) A data mining framework (Kurgan & Musilek, 2006) to derive new constructs in old data; 2) Robust linear and logistic regression models (e.g. MLR, FIML; Muthen & Muthen, 2017); 3) Zero-inflated mixture modelling (Wall et al., 2015) to estimate an ADHD severity score; 4) Machine learning (vselect; Lindsey & Sheather, 2010) to aid selection of an optimal set of covariates for quasi-experimental matching; and 5) Coarsened Exact Matching (CEM; Iacus et al., 2014) to derive a weighted matched sample of ADHD children and similar controls. Key findings: A DSM-5 ADHD subgroup and subtypes were retrospectively derived and validated using age 10 BCS70 data (N=11,426; nADHD=594, 5.2% prevalence, 30% girls, 46% inattentive subtype). Overall prevalence aligned with epidemiology estimates, but the relatively high percentages of ADHD girls and inattentive cases enabled rare new insights for these groups. The distribution of the ADHD severity score (N=11,426, M=0.06, SD=0.91) supported dimensionality of the construct. Stressful life events, chronic stressors, self-esteem and locus of control significantly predicted DSM-5 ADHD symptomatology and explained 19.5% of the ADHD severity score at age 10 (N=11,426), supporting State Regulation Theory at the psychosocial construct level. Quasi-experimental methods were employed to create a pruned longitudinal sample of ADHD and control cohort members matched on evidence-based confounds (N=6,207). Regression models on this sample did not support a significant effect of childhood ADHD on adult outcomes, contrary to prevailing evidence from mostly clinical samples matched on fewer confounds. Matching confounds used were sex, father’s education, depressed mother, mother smoked during pregnancy, childhood wheezing, and low standard home. Replication and refinement are needed, but the finding suggests future experimental studies should consider stratifying samples on these factors, and that ADHD per se may not drive poor outcomes. In the matched sample (N=6,207), age 10 maths scores (boys and girls), externalising problems, and engagement in leisure activity (girls only), were significant factors predicting a continuous composite measure of adult subjective wellbeing. Parent education, age 10 maths, reading (boys and girls), locus of control, and authoritarian child-rearing views (girls only), were significant childhood factors predicting a dichotomous academic qualification measure of adult educational attainment, as a proxy for SES/objective wellbeing. All effect sizes were small . In a longitudinal ADHD subsample (n=369), age 10 chronic stressors, externalising problems, and reading significantly predicted adult subjective wellbeing, explaining 7.1% of variance (boys and girls). Father’s education and age 10 reading significantly predicted adult educational attainment. The effects of chronic stressors and reading, and the higher proportion of girls and inattentive ADHD cases in the sample provide novel insights which should be translatable into teacher training and practice. Findings are applicable internationally, subject to demographic generalisability parameters.ESRC Advanced Quantitative Methods Studentship, Hughes Hall Scholarshi

The origins and consequences of attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is characterized by developmentally inappropriate levels of inattention, hyperactivity, and impulsivity, and is the most common neurodevelopmental disorder of childhood. This highly prevalent disorder is estimated to affect about 5% of school-age children worldwide, with a substantial degree of persistence over time. Although the specific cause of ADHD is still largely unknown, despite a long history of research, it is believed to involve multiple genetic and environmental factors. ADHD is also associated with considerable comorbidities and functional impairments, which place a substantial burden on affected individuals, their families and society. Stimulant medication is considered as one of the most important treatments for ADHD, but the increased use over the years has also raised numerous public concerns. Therefore, the general aim of this thesis was to investigate how genetic and environmental factors contribute to the development of ADHD, as well as to investigate the consequences of ADHD and potential effects of ADHD medication. Study I explored the relative contribution of genetic and environmental influences of ADHD from childhood through early adulthood. The study found that the shared view of self- and informant-rated ADHD is highly heritable in childhood, adolescence, and early adulthood. It also found evidence of both stable and dynamic genetic influences on ADHD over the course of the development. Study II examined the association between young maternal age at childbearing and subsequent risk for ADHD in offspring, using a genetically-informative design. The study found that maternal age at first birth, not maternal age at the current birth, predicted offspring ADHD. Thus, all offspring born to teenage mothers were at increased risk of ADHD. The association was mainly explained by passive gene-environment correlations. That is, genetic factors transmitted from mothers to children contribute to both mothers’ age at childbearing and ADHD in offspring. Study III investigated how the two symptom dimensions of ADHD (hyperactivity-impulsivity and inattention) are associated with early-onset substance use. The study found that that hyperactivity-impulsivity, but not inattention, independently predicted early-onset tobacco use, even after controlling for conduct problems. Twin analyses showed that the association between hyperactivity-impulsivity and early-onset substance use were mainly influenced by genetic factors. Study IV estimated the association between ADHD and the risk of serious transport accidents, and explored the extent to which ADHD medication influenced this risk among ADHD patients. The study found that ADHD patients were at increased risk for serious transport accidents, and that ADHD medication was associated with a significant reduction of accidents, among males patients, even when using within-individual analyses to control for confounding. Study V explored whether stimulant ADHD medication is associated with risk for long-term substance abuse. The study found no indication of increased substance abuse at follow-up. Rather, the results suggested there was a decrease in substance abuse for up to four years after taking ADHD medications, and that patients who took ADHD medication for longer durations had lower rates of substance abuse. In conclusion, ADHD is a prevalent, persistent and impairing disorder. Genetic factors play an important role in the development of the disorder from childhood to adulthood. ADHD predicts poor developmental and health outcomes, and ADHD medications appear to be useful in reducing some serious adverse outcomes, such as transport accidents and substance abuse. The findings in this thesis highlight the importance of using quasi-experimental designs, including genetically-informative studies, when exploring how risk factors and adverse consequences are associated with ADHD

Is police misconduct contagious? Non-trivial null findings from Dallas, Texas

Objectives: Understanding if police malfeasance might be “contagious” is vital to identifying efficacious paths to police reform. Accordingly, we investigate whether an officer’s propensity to engage in misconduct is associated with her direct, routine interaction with colleagues who have themselves engaged in misbehavior in the past. Methods: Recognizing the importance of analyzing the actual social networks spanning a police force, we use data on collaborative responses to 1,165,136 “911” calls for service by 3475 Dallas Police Department (DPD) officers across 2013 and 2014 to construct daily networks of front-line interaction. And we relate these cooperative networks to reported and formally sanctioned misconduct on the part of the DPD officers during the same time period using repeated-events survival models. Results: Estimates indicate that the risk of a DPD officer engaging in misconduct is not associated with the disciplined misbehavior of her ad hoc, on-the-scene partners. Rather, a greater risk of misconduct is associated with past misbehavior, officer-specific proneness, the neighborhood context of patrol, and, in some cases, officer race, while departmental tenure is a mitigating factor. Conclusions: Our observational findings—based on data from one large police department in the United States—ultimately suggest that actor-based and ecological explanations of police deviance should not be summarily dismissed in favor of accounts emphasizing negative socialization, where our study design also raises the possibility that results are partly driven by unobserved trait-based variation in the situations that officers find themselves in. All in all, interventions focused on individual officers, including the termination of deviant police, may be fruitful for curtailing police misconduct—where early interventions focused on new offenders may be key to avoiding the escalation of deviance

Protocol for investigating genetic determinants of posttraumatic stress disorder in women from the Nurses' Health Study II

<p>Abstract</p> <p>Background</p> <p>One in nine American women will meet criteria for the diagnosis of posttraumatic stress disorder (PTSD) in their lifetime. Although twin studies suggest genetic influences account for substantial variance in PTSD risk, little progress has been made in identifying variants in specific genes that influence liability to this common, debilitating disorder.</p> <p>Methods and design</p> <p>We are using the unique resource of the Nurses Health Study II, a prospective epidemiologic cohort of 68,518 women, to conduct what promises to be the largest candidate gene association study of PTSD to date. The entire cohort will be screened for trauma exposure and PTSD; 3,000 women will be selected for PTSD diagnostic interviews based on the screening data. Our nested case-control study will genotype1000 women who developed PTSD following a history of trauma exposure; 1000 controls will be selected from women who experienced similar traumas but did not develop PTSD.</p> <p>The primary aim of this study is to detect genetic variants that predict the development of PTSD following trauma. We posit inherited vulnerability to PTSD is mediated by genetic variation in three specific neurobiological systems whose alterations are implicated in PTSD etiology: the hypothalamic-pituitary-adrenal axis, the locus coeruleus/noradrenergic system, and the limbic-frontal neuro-circuitry of fear. The secondary, exploratory aim of this study is to dissect genetic influences on PTSD in the broader genetic and environmental context for the candidate genes that show significant association with PTSD in detection analyses. This will involve: conducting conditional tests to identify the causal genetic variant among multiple correlated signals; testing whether the effect of PTSD genetic risk variants is moderated by age of first trauma, trauma type, and trauma severity; and exploring gene-gene interactions using a novel gene-based statistical approach.</p> <p>Discussion</p> <p>Identification of liability genes for PTSD would represent a major advance in understanding the pathophysiology of the disorder. Such understanding could advance the development of new pharmacological agents for PTSD treatment and prevention. Moreover, the addition of PTSD assessment data will make the NHSII cohort an unparalleled resource for future genetic studies of PTSD as well as provide the unique opportunity for the prospective examination of PTSD-disease associations.</p