Contamination bias in the estimation of child maltreatment causal effects on adolescent internalizing and externalizing behavior problems.

BACKGROUND: When unaddressed, contamination in child maltreatment research, in which some proportion of children recruited for a nonmaltreated comparison group are exposed to maltreatment, downwardly biases the significance and magnitude of effect size estimates. This study extends previous contamination research by investigating how a dual-measurement strategy of detecting and controlling contamination impacts causal effect size estimates of child behavior problems. METHODS: This study included 634 children from the LONGSCAN study with 63 cases of confirmed child maltreatment after age 8 and 571 cases without confirmed child maltreatment. Confirmed child maltreatment and internalizing and externalizing behaviors were recorded every 2 years between ages 4 and 16. Contamination in the nonmaltreated comparison group was identified and controlled by either a prospective self-report assessment at ages 12, 14, and 16 or by a one-time retrospective self-report assessment at age 18. Synthetic control methods were used to establish causal effects and quantify the impact of contamination when it was not controlled, when it was controlled for by prospective self-reports, and when it was controlled for by retrospective self-reports. RESULTS: Rates of contamination ranged from 62% to 67%. Without controlling for contamination, causal effect size estimates for internalizing behaviors were not statistically significant. Causal effects only became statistically significant after controlling contamination identified from either prospective or retrospective reports and effect sizes increased by between 17% and 54%. Controlling contamination had a smaller impact on effect size increases for externalizing behaviors but did produce a statistically significant overall effect, relative to the model ignoring contamination, when prospective methods were used. CONCLUSIONS: The presence of contamination in a nonmaltreated comparison group can underestimate the magnitude and statistical significance of causal effect size estimates, especially when investigating internalizing behavior problems. Addressing contamination can facilitate the replication of results across studies.

Controlling contamination in child maltreatment research: Impact on effect size estimates for child behavior problems measured throughout childhood and adolescence.

Contamination, when members of a comparison or control condition are exposed to the event or intervention under scientific investigation, is a methodological phenomenon that downwardly biases the magnitude of effect size estimates. This study tested a novel approach for controlling contamination in observational child maltreatment research. Data from The Longitudinal Studies of Child Abuse and Neglect (LONGSCAN; N = 1354) were obtained to estimate the risk of confirmed child maltreatment on trajectories of internalizing and externalizing behaviors before and after controlling contamination. Baseline models, where contamination was uncontrolled, demonstrated a risk for greater internalizing (b = .29, p < .001, d = .40) and externalizing (b = .14, p = .040, d = .19) behavior trajectories. Final models, where contamination was controlled by separating the comparison condition into subgroups that did or did not self-report maltreatment, also demonstrated risks for greater internalizing (b = .37, p < .001, d = .51) and externalizing (b = .22, p = .028, d = .29) behavior trajectories. However, effect size estimates in final models were 27.5%-52.6% larger compared to baseline models. Controlling contamination in child maltreatment research can strengthen effect size estimates for child behavior problems, aiding future child maltreatment research design and analysis.

Contamination in Observational Research on Child Maltreatment: A Conceptual and Empirical Review With Implications for Future Research.

Contamination is a methodological phenomenon occurring in child maltreatment research when individuals in an established comparison condition have, in reality, been exposed to maltreatment during childhood. The current paper: (1) provides a conceptual and methodological introduction to contamination in child maltreatment research, (2) reviews the empirical literature demonstrating that the presence of contamination biases causal estimates in both prospective and retrospective cohort studies of child maltreatment effects, (3) outlines a dual measurement strategy for how child maltreatment researchers can address contamination, and (4) describes modern statistical methods for generating causal estimates in child maltreatment research after contamination is controlled. Our goal is to introduce the issue of contamination to researchers examining the effects of child maltreatment in an effort to improve the precision and replication of causal estimates that ultimately inform scientific and clinical decision-making as well as public policy.

Patterns of literacy among U.S. students.

How well do U.S. students read? In this article, Sean Reardon, Rachel Valentino, and Kenneth Shores rely on studies using data from national and international literacy assessments to answer this question. In part, the answer depends on the specific literacy skills assessed. The authors show that almost all U.S. students can "read" by third grade, if reading is defined as proficiency in basic procedural word-reading skills. But reading for comprehension--integrating background knowledge and contextual information to make sense of a text--requires a set of knowledge-based competencies in addition to word-reading skills. By the standards used in various large-scale literacy assessments, only about a third of U.S. students in middle school possess the knowledge-based competencies to "read" in this more comprehensive sense. This low level of literacy proficiency does not appear to be a result of declining performance over time. Literacy skills of nine-year-olds in the United States have increased modestly over the past forty years, while the skills of thirteen- and seventeen-year-olds have remained relatively flat. Literacy skills vary considerably among students, however. For example, the literacy skills of roughly 10 percent of seventeen-year-olds are at the level of the typical nine-year-old. This variation is patterned in part by race, ethnicity, and socioeconomic background. Black and Hispanic students enter high school with average literacy skills three years behind those of white and Asian students; students from low-income families enter high school with average literacy skills five years behind those of high-income students. These are gaps that no amount of remedial instruction in high school is likely to eliminate. And while the racial and ethnic disparities are smaller than they were forty to fifty years ago, socioeconomic disparities in literacy skills are growing. Nor is the low level of literacy skills particularly a U.S. phenomenon. On international comparisons, American students perform modestly above average compared with those in other developed countries (and well above average among a larger set of countries). Moreover, there is no evidence that U.S. students lose ground relative to those in other countries during the middle school years. Thus, although literacy skills in the United States are lower than needed to meet the demands of modern society, the same is true in most other developed countries.