Jane Hammond

The PhenX Toolkit: Get the Most From Your Measures

The potential for genome-wide association studies to relate phenotypes to specific genetic variation is greatly increased when data can be combined or compared across multiple studies. To facilitate replication and validation across studies, RTI International (Research Triangle Park, North Carolina) and the National Human Genome Research Institute (Bethesda, Maryland) are collaborating on the consensus measures for Phenotypes and eXposures (PhenX) project. The goal of PhenX is to identify 15 high-priority, well-established, and broadly applicable measures for each of 21 research domains. PhenX measures are selected by working groups of domain experts using a consensus process that includes input from the scientific community. The selected measures are then made freely available to the scientific community via the PhenX Toolkit. Thus, the PhenX Toolkit provides the research community with a core set of high-quality, well-established, low-burden measures intended for use in large-scale genomic studies. PhenX measures will have the most impact when included at the experimental design stage. The PhenX Toolkit also includes links to standards and resources in an effort to facilitate data harmonization to legacy data. Broad acceptance and use of PhenX measures will promote cross-study comparisons to increase statistical power for identifying and replicating variants associated with complex diseases and with gene-gene and gene-environment interactions.

Impact of prenatal cocaine exposure on child behavior problems through school age.

OBJECTIVE. We examined the trajectory of childhood behavior problems after prenatal cocaine exposure. METHODS. The Maternal Lifestyle Study, a longitudinal cohort study, enrolled children between 1993 and 1995 at 4 centers. Prenatal cocaine exposure was determined from mothers who admitted use and/or meconium results. Exposed children were matched with a group of nonexposed children within site and by gestational age, gender, race, and ethnicity. The study began at the 1-month corrected age with a total of 1388 children enrolled. A total of 1056 were assessed for internalizing, externalizing, and total behavior problems at ages 3, 5, and 7 years using the Child Behavior Checklist. Longitudinal hierarchical linear models were used to determine the effect of prenatal cocaine exposure on behavior problem trajectories while controlling for other prenatal exposures; time-varying covariates, including ongoing caregiver use of legal and illegal substances; demographic factors; family violence; and caregiver psychological distress. RESULTS. High prenatal cocaine exposure was associated with the trajectory of internalizing, externalizing, and total behavior problems; these effects were independent of and less than the significant combined effect of prenatal and postnatal tobacco and alcohol exposures. Caregiver depression and family violence had independent negative influence on all behavior outcomes. CONCLUSIONS. Prenatal cocaine exposure has a negative impact on the trajectories of childhood behavior outcomes. When they co-occur with prenatal cocaine exposure, prenatal and postnatal tobacco and alcohol exposures have added negative effects on behavior outcomes.

PhenX: a toolkit for interdisciplinary genetics research.

Purpose of review To highlight standard PhenX (consensus measures for Phenotypes and eXposures) measures for nutrition, dietary supplements, and cardiovascular disease research and to demonstrate how these and other PhenX measures can be used to further interdisciplinary genetics research. Recent findings PhenX addresses the need for standard measures in large-scale genomic research studies by providing investigators with high-priority, well established, low-burden measurement protocols in a web-based toolkit (https://www.phenxtoolkit.org). Cardiovascular and Nutrition and Dietary Supplements are just 2 of 21 research domains and accompanying measures included in the PhenX Toolkit. Summary Genome-wide association studies (GWAS) provide promise for the identification of genomic markers associated with different disease phenotypes, but require replication to validate results. Cross-study comparisons typically increase statistical power and are required to understand the roles of comorbid conditions and environmental factors in the progression of disease. However, the lack of comparable phenotypic, environmental, and risk factor data forces investigators to infer and to compare metadata rather than directly combining data from different studies. PhenX measures provide a common currency for collecting data, thereby greatly facilitating cross-study analysis and increasing statistical power for identification of associations between genotypes, phenotypes, and exposures.

The Combined Effects of Prenatal Drug Exposure and Early Adversity on Neurobehavioral Disinhibition in Childhood and Adolescence

The negative effects of prenatal substance exposure on neurobiological and psychological development and of early adversity are clear, but little is known about their combined effects. In this study, multilevel analyses of the effects of prenatal substance exposure and early adversity on the emergence of neurobehavioral disinhibition in adolescence were conducted. Neurobehavioral disinhibition has previously been observed to occur frequently in multiproblem youth from high-risk backgrounds. In the present study, neurobehavioral disinhibition was assessed via behavioral dysregulation and poor executive function composite measures. Data were drawn from a prospective longitudinal investigation of prenatal substance exposure that included 1,073 participants followed from birth through adolescence. The results from latent growth modeling analyses showed mean stability but significant individual differences in behavioral dysregulation and mean decline with individual differences in executive function difficulties. Prior behavioral dysregulation predicted increased executive function difficulties. Prenatal drug use predicted the emergence and growth in neurobehavioral disinhibition across adolescence (directly for behavioral dysregulation and indirectly for executive function difficulties via early adversity and behavioral dysregulation). Prenatal drug use and early adversity exhibited unique effects on growth in behavioral dysregulation; early adversity uniquely predicted executive function difficulties. These results are discussed in terms of implications for theory development, social policy, and prevention science.

Differential Relationships Between Personal and Community Stressors and Children’s Neurocognitive Functioning

Early adversity can alter development of neurocognition, including executive cognitive and emotional regulatory functions. This is the first study to explore differential relationships between personal (physical and emotional abuse and neglect, school and parental stressors) and community (neighborhood problems and witnessing neighborhood violence) stressors and neurocognition. Predominantly Latino children ( n = 553) aged 10 to 12 years completed tasks measuring intelligence, impulsivity, problem solving, cognitive flexibility, decision making, and emotion attributions. Adjusting for age and parent education, bivariate regression analyses found exposure to personal stressors to be associated with relative deficits in at least one neurocognitive function. Community stressors were related to relative deficits in emotion attributions and problem solving. In multivariate analyses, neglect was related to misattributions of emotion and IQ deficits, and physical abuse was related to problem solving. Community stressors were not correlated with neurocognition when viewed relative to personal stressors. Stressor types were differentially associated with performance on specific neurocognitive tasks.

Cognitive Outcomes After Neonatal Encephalopathy

OBJECTIVES: To describe the spectrum of cognitive outcomes of children with and without cerebral palsy (CP) after neonatal encephalopathy, evaluate the prognostic value of early developmental testing and report on school services and additional therapies. METHODS: The participants of this study are the school-aged survivors of the National Institute of Child Health and Human Development Neonatal Research Network randomized controlled trial of whole-body hypothermia. Children underwent neurologic examinations and neurodevelopmental and cognitive testing with the Bayley Scales of Infant Development–II at 18 to 22 months and the Wechsler intelligence scales and the Neuropsychological Assessment–Developmental Neuropsychological Assessment at 6 to 7 years. Parents were interviewed about functional status and receipt of school and support services. We explored predictors of cognitive outcome by using multiple regression models. RESULTS: Subnormal IQ scores were identified in more than a quarter of the children: 96% of survivors with CP had an IQ <70, 9% of children without CP had an IQ <70, and 31% had an IQ of 70 to 84. Children with a mental developmental index <70 at 18 months had, on average, an adjusted IQ at 6 to 7 years that was 42 points lower than that of those with a mental developmental index >84 (95% confidence interval, −49.3 to −35.0; P < .001). Twenty percent of children with normal IQ and 28% of those with IQ scores of 70 to 84 received special educational support services or were held back ≥1 grade level. CONCLUSIONS: Cognitive impairment remains an important concern for all children with neonatal encephalopathy.

Neurobehavioral Disinhibition Predicts Initiation of Substance Use in Children with Prenatal Cocaine Exposure

BACKGROUND In previous work we (Fisher et al., 2011) examined the emergence of neurobehavioral disinhibition (ND) in adolescents with prenatal substance exposure. We computed ND factor scores at three age points (8/9, 11 and 13/14 years) and found that both prenatal substance exposure and early adversity predicted ND. The purpose of the current study was to determine the association between these ND scores and initiation of substance use between ages 8 and 16 in this cohort as early initiation of substance use has been related to later substance use disorders. Our hypothesis was that prenatal cocaine exposure predisposes the child to ND, which, in turn, is associated with initiation of substance use by age 16. METHODS We studied 386 cocaine exposed and 517 unexposed children followed since birth in a longitudinal study. Five dichotomous variables were computed based on the subjects report of substance use: alcohol only; tobacco only; marijuana only; illicit substances and any substance. RESULTS Cox proportional hazard regression showed that the 8/9 year ND score was related to initiation of alcohol, tobacco, illicit and any substance use but not marijuana use. The trajectory of ND across the three age periods was related to substance use initiation in all five substance use categories. Prenatal cocaine exposure, although initially related to tobacco, marijuana and illicit substance initiation, was no longer significant with ND scores in the models. CONCLUSION Prenatal drug exposure appears to be a risk pathway to ND, which by 8/9 years portends substance use initiation.

Violence and Delinquency, Early Onset Drug Use, and Psychopathology in Drug-Exposed Youth at 11 Years

Abstract:  In this first study of violence and resilience in 517 youth exposed to cocaine and other drugs during pregnancy, we identified specific links between four types of violence and delinquency, drug use, and psychopathology in early adolescence. Further, positive and interpersonal attributes promoted resilience in the face of exposure to violence and other risks. This study provides new evidence for the impact of violence as well as resilience against disruptive forms of psychopathology and behavior.

Protective factors can mitigate behavior problems after prenatal cocaine and other drug exposures

BACKGROUND: We determined the role of risk and protective factors on the trajectories of behavior problems associated with high prenatal cocaine exposure (PCE)/polydrug exposure. METHODS: The Maternal Lifestyle Study enrolled 1388 children with or without PCE, assessed through age 15 years. Because most women using cocaine during pregnancy also used other substances, we analyzed for the effects of 4 categories of prenatal drug exposure: high PCE/other drugs (OD), some PCE/OD, OD/no PCE, and no PCE/no OD. Risks and protective factors at individual, family, and community levels that may be associated with behavior outcomes were entered stepwise into latent growth curve models, then replaced by cumulative risk and protective indexes, and finally by a combination of levels of risk and protective indexes. Main outcome measures were the trajectories of externalizing, internalizing, total behavior, and attention problems scores from the Child Behavior Checklist (parent). RESULTS: A total of 1022 (73.6%) children had known outcomes. High PCE/OD significantly predicted externalizing, total, and attention problems when considering the balance between risk and protective indexes. Some PCE/OD predicted externalizing and attention problems. OD/no PCE also predicted behavior outcomes except for internalizing behavior. High level of protective factors was associated with declining trajectories of problem behavior scores over time, independent of drug exposure and risk index scores. CONCLUSIONS: High PCE/OD is a significant risk for behavior problems in adolescence; protective factors may attenuate its detrimental effects. Clinical practice and public health policies should consider enhancing protective factors while minimizing risks to improve outcomes of drug-exposed children.

Risk-Taking Behavior Among Adolescents with Prenatal Drug Exposure and Extrauterine Environmental Adversity

Objective: High-risk environments characterized by familial substance use, poverty, inadequate parental monitoring, and violence exposure are associated with an increased propensity for adolescents to engage in risk-taking behaviors (e.g., substance use, sexual behavior, and delinquency). However, additional factors such as drug exposure in utero and deficits in inhibitory control among drug-exposed youth may further influence the likelihood that adolescents in high-risk environments will engage in risk-taking behavior. This study examined the influence of prenatal substance exposure, inhibitory control, and sociodemographic/environmental risk factors on risk-taking behaviors in a large cohort of adolescents with and without prenatal cocaine exposure (PCE). Method: Risk-taking behavior (delinquency, substance use, and sexual activity) was assessed in 963 adolescents (433 cocaine-exposed, 530 nonexposed) at 15 years of age. Results: Prenatal cocaine exposure predicted later arrests and early onset of sexual behavior in controlled analyses. Associations were partially mediated, however, by adolescent inhibitory control problems. PCE was not associated with substance use at this age. In addition, male gender, low parental involvement, and violence exposure were associated with greater odds of engaging in risk-taking behavior across the observed domains. Conclusions: Study findings substantiate concern regarding the association between prenatal substance exposure and related risk factors and the long-term outcomes of exposed youth. Access to the appropriate social, educational, and medical services is essential in preventing and intervening with risk-taking behaviors and the potential consequences (e.g., adverse health outcomes and incarceration), especially among high-risk adolescent youth and their families.