Prenatal smoking and genetic risk: examining the childhood origins of externalizing behavioral problems

A Critical Review of Statistical Methods for Twin Studies Relating Exposure to Early Life Health Conditions

When investigating disease etiology, twin data provide a unique opportunity to control for confounding and disentangling the role of the human genome and exposome. However, using appropriate statistical methods is fundamental for exploiting such potential. We aimed to critically review the statistical approaches used in twin studies relating exposure to early life health conditions. We searched PubMed, Scopus, Web of Science, and Embase (2011–2021). We identified 32 studies and nine classes of methods. Five were conditional approaches (within-pair analyses): additive-common-erratic (ACE) models (11 studies), generalized linear mixed models (GLMMs, five studies), generalized linear models (GLMs) with fixed pair effects (four studies), within-pair difference analyses (three studies), and paired-sample tests (two studies). Four were marginal approaches (unpaired analyses): generalized estimating equations (GEE) models (five studies), GLMs with cluster-robust standard errors (six studies), GLMs (one study), and independent-sample tests (one study). ACE models are suitable for assessing heritability but require adaptations for binary outcomes and repeated measurements. Conditional models can adjust by design for shared confounders, and GLMMs are suitable for repeated measurements. Marginal models may lead to invalid inference. By highlighting the strengths and limitations of commonly applied statistical methods, this review may be helpful for researchers using twin designs.

Parent Exposure to Drugs: A “New” Adverse Childhood Experience With Devastating Behavioral Consequences

Household drug abuse is one of the seminal forms of adverse childhood experiences, but it does not fully capture the severity of parents that actively provide or even administer drugs to their children. Drawing on a near population of federal supervised release offenders, the current study examined this “new” adverse childhood experience and its association with antisociality. Multiple analytical techniques (e.g., correlation, binary and multinomial logistic regression, and negative binomial regression) indicated that parent exposure to drugs was significantly associated with current drug status while on supervision, three forms of drug offending, and Cannabis, Cocaine, Methamphetamine, Opiate, and Alcohol Dependence even while controlling for age of arrest onset, sex, race, and current age. We concur with other scholars that more conceptualization and measurement-refinement of adverse childhood experiences is needed to fully understand how early-life trauma shapes the contours of the criminal career.

Statistical Approaches for Estimating Sex-Specific Effects in Endocrine Disruptors Research

BACKGROUND

When a biologic mechanism of interest is anticipated to operate differentially according to sex, as is often the case in endocrine disruptors research, investigators routinely estimate sex-specific associations. Less attention has been given to potential sexual heterogeneity of confounder associations with outcomes. When relationships of covariates with outcomes differ according to sex, commonly applied statistical approaches for estimating sex-specific endocrine disruptor effects may produce divergent estimates.

OBJECTIVES

We discuss underlying assumptions and evaluate the performance of two traditional approaches for estimating sex-specific effects, stratification and product terms, and introduce a simple modeling alternative: an augmented product term approach.

METHODS

We describe the impact of assumptions regarding sexual heterogeneity of confounder relationships on estimates of sex-specific effects of the exposure of interest for three approaches: stratification, traditional product terms, and augmented product terms. Using simulated and applied examples, we demonstrate properties of each approach under a range of scenarios.

RESULTS

In simulations, sex-specific exposure effects estimated using the traditional product term approach were biased when confounders had sex-dependent associations with the outcome. Sex-specific estimates from stratification and the augmented product term approach were unbiased but less precise. In the applied example, the three approaches yielded similar estimates, but resulted in some meaningful differences in conclusions based on statistical significance.

CONCLUSIONS

Investigators should consider sexual heterogeneity of confounder associations when choosing an analytic approach to estimate sex-specific effects of endocrine disruptors on health. In the presence of sex-dependent confounding, our augmented product term approach may be advantageous over stratification when there is prior knowledge available to fit reduced models or when investigators seek an automated test for effect measure modification. https://doi.org/10.1289/EHP334.

Breastfeeding duration and offspring conduct problems: The moderating role of genetic risk

RATIONALE

A sizable body of research has examined associations between breastfeeding and various facets of offspring development, including childhood behavioral problems. Notwithstanding the number of studies on the topic, breastfeeding has not consistently been linked to child misbehaviors. Moreover, empirical examinations of whether breastfeeding is differentially predictive of conduct problems among individuals with varying degrees of genetic risk are lacking.

OBJECTIVE

The present study examines whether a short duration of breastfeeding and genetic risk interact to predict conduct problems during childhood.

METHODS

A genetically informative design is employed to examine a subsample of twins from the Early Childhood Longitudinal Study: Birth Cohort (ECLS-B), a nationally representative sample of American children.

RESULTS

The findings suggest that a shorter duration of breastfeeding only enhances the risk of offspring conduct problems among children who possess high levels of genetic risk. Conversely, longer breastfeeding durations were found to protect against childhood behavioral problems when genetic risk was high.

CONCLUSIONS

Indicators of genetic risk may help to distinguish individuals whose behavioral development is most sensitive to the duration of breastfeeding. Future research should seek to replicate and extend these findings by considering genetic factors as potential markers of differential susceptibility to breastfeeding duration.