Sibling differences in low birth weight, dopaminergic polymorphisms, and ADHD symptomatology: evidence of GxE

The Interplay Between Prenatal Adversity, Offspring Dopaminergic Genes, and Early Parenting on Toddler Attentional Function

Background: Few studies have explored the complex gene-by-prenatal environment-by-early postnatal environment interactions that underlie the development of attentional competence. Here, we examined if variation in dopamine-related genes interacts with prenatal adversity to influence toddler attentional competence and whether this influence is buffered by early positive maternal behavior. Methods: From the Maternal Adversity, Vulnerability and Neurodevelopment cohort, 134 participants (197 when imputing missing data) had information on prenatal adversity (prenatal stressful life events, prenatal maternal depressive symptoms, and birth weight), five dopamine-related genes (DAT1, DRD4, DRD2, COMT, BDNF), observed maternal parenting behavior at 6 months and parent-rated toddler attentional competence at 18 and 24 months. The Latent Environmental and Genetic Interaction (LEGIT) approach was used to examine genes-by-prenatal environment-by-postnatal environment interactions while controlling for sociodemographic factors and postnatal depression. Results: Our hypothesis of a three-way interaction between prenatal adversity, dopamine-related genes, and early maternal parenting behavior was not confirmed. However, consistent two-way interactions emerged between prenatal adversity and dopamine-related genes; prenatal adversity and maternal parenting behavior, and dopamine-related genes and maternal parenting behavior in relation to toddler attentional competence. Significant interaction effects were driven by the DAT1, COMT, and BDNF genotypes; prenatal stressful life events; maternal sensitivity, tactile stimulation, vocalization, and infant-related activities. Conclusions: Multiple dopamine-related genes affected toddler attentional competence and they did so in interaction with prenatal adversity and the early rearing environment, separately. Effects were already visible in young children. Several aspects of early maternal parenting have been identified as potential targets for intervention.

Physical Activity in 6.5-Year-Old Children Born Extremely Preterm

Physical activity (PA) can prevent cardiovascular diseases. Because of increased risks of impairments affecting motor activity, PA in children born preterm may differ from that in children born at term. In this prospective cohort study, we compared objectively measured PA in 71 children born extremely preterm (<27 weeks gestational age), to their 87 peers born at term, at 6.5 years of age. PA measured with accelerometer on the non-dominant wrist for 7 consecutive days was compared between index and control children and analyzed for associations to prenatal growth, major neonatal brain injury, bronchopulmonary dysplasia and neonatal septicemia, using ANOVA. Boys born extremely preterm spent on average 22 min less time per day in moderate to vigorous physical activity (MVPA) than control boys (95% CI: -8, -37). There was no difference in girls. Amongst children born extremely preterm, major neonatal brain injury was associated with 56 min less time in MVPA per day (95%CI: -88, -26). Subgroups of children born extremely preterm exhibit lower levels of physical activity which may be a contributory factor in the development of cardiovascular diseases as adults.

Disadvantaged neighborhoods, birth weight, and problem behavior in five- and six-year-old pre-school children: Evidence from a cohort born in Amsterdam

RATIONALE

Low birth weight has been found to increase the problem behavior of children. Yet, little attention has been given to adequately account for the impact of the child's neighborhood on this relation. The residential neighborhood is a choice, based on factors that are usually not observed that may also influence birth weight and problem behavior.

OBJECTIVE

Using a model that accounts for such endogeneity of both neighborhood choice and birth weight, we have analyzed behavioral problems in 4210 pre-school children between the ages of 5 and 6, birth weight, and neighborhood status, simultaneously.

METHOD

The data used are from the Amsterdam Born Children and their Development (ABCD) cohort for whom a complete prospective record of birth outcomes, pregnancy, socio-demographic characteristics, and indicators of problem behavior are available. Neighborhood data obtained from Statistics Netherlands are merged with the ABCD data file.

RESULTS

Our results suggest that ignoring endogeneity attenuates the effect of disadvantaged neighborhoods on both birth weight and problem behavior in pre-school children. Living in a disadvantaged neighborhood decreases the birth weight and increases the probability of problem behavior. Accounting for the endogeneity of neighborhood choice increases the estimated impacts (marginal effects: from -10% to -44% for birth weight and from 3% to 11% for problem behavior). Lower birth weight increases the probability of problem behavior, but it is only significant after adjusting for endogeneity. The coefficients of other factors have the expected associations with problem behavior.

CONCLUSIONS

These significant effects of disadvantaged neighborhood on birth weight and problem behavior could inform policies and practices that improve neighborhood development for children born in Amsterdam.

Early environmental risk factors for neurodevelopmental disorders - a systematic review of twin and sibling studies

While neurodevelopmental disorders (NDDs) are highly heritable, several environmental risk factors have also been suggested. However, the role of familial confounding is unclear. To shed more light on this, we reviewed the evidence from twin and sibling studies. A systematic review was performed on case control and cohort studies including a twin or sibling within-pair comparison of neurodevelopmental outcomes, with environmental exposures until the sixth birthday. From 7,315 screened abstracts, 140 eligible articles were identified. After adjustment for familial confounding advanced paternal age, low birth weight, birth defects, and perinatal hypoxia and respiratory stress were associated with autism spectrum disorder (ASD), and low birth weight, gestational age and family income were associated with attention-deficit/hyperactivity disorder (ADHD), categorically and dimensionally. Several previously suspected factors, including pregnancy-related factors, were deemed due to familial confounding. Most studies were conducted in North America and Scandinavia, pointing to a global research bias. Moreover, most studies focused on ASD and ADHD. This genetically informed review showed evidence for a range of environmental factors of potential casual significance in NDDs, but also points to a critical need of more genetically informed studies of good quality in the quest of the environmental causes of NDDs.

A Meta-Analysis of the Association Between Birth Weight and Attention Deficit Hyperactivity Disorder

A large body of work has investigated the association between birth weight and ADHD and has resulted in mixed findings with regard to the direction and magnitude of this association. Despite the vast amount of research on this topic, a comprehensive and systematic quantification of the association between birth weight and ADHD has yet to be undertaken. A meta-analysis of 88 unique studies (N = 4,645,482) was conducted to quantify the overall effect size of birth weight on ADHD symptoms. Several variables were examined as moderators that may contribute to systematic variation in effect sizes. Overall, birth weight was found to have a small, but significant, association with ADHD symptoms such that individuals born at lower birth weights manifested greater symptoms of ADHD (r = -0.15). Sample type, mean birth weight of the sample, geographic region, the informant of ADHD symptoms, ADHD symptom measurement method, and race were all found to contribute significantly to heterogeneity in effect sizes. Notably, several early life risk factors previously found to be associated with both ADHD and birth weight, gestational age and prenatal smoking exposure, were not found to contribute to heterogeneity in effect sizes. The findings of the current analyses align with the growing recognition that early life adversity contributes to neurodevelopmental difficulties, and the findings highlight the importance of a better understanding of the mechanisms underlying the association between early life risk factors and adverse neurodevelopmental sequela, such as that observed in ADHD.

[Topics on Child Development in Pediatrics]

Over the past few decades, advances in neonatal medicine have increased survival rates among very-low-birth-weight (VLBW) babies. Despite improvements in short-term outcomes, there is increasing concern about the probability of mild cognitive dysfunction in this population. Our analysis of VLBW babies born in our hospital revealed that the incidence of mild developmental disorders including autism spectrum disorder (ASD) and attention deficit hyperactive disorder (ADHD) at the age of 3 years is 7.2%, which is markedly higher than the 2.8% incidence of ASD in the general population. Because problems related to ASD or ADHD tend to become more prominent as children grow up, the ages at diagnosis of developmental disorders are generally 6 years or above. Thus, in our follow up study of VLBW babies at age 6, the incidence of these developmental disorders had risen to 30%. These patients are apparently obstinate and difficult to train, causing parental problems with child care. It is important to support these children and help them establish good relationships with their parents. Given these problems, it is necessary to follow up VLBW children in the longterm, at least until they are elementary school students.

The Interplay Between Early Father Involvement and Neonatal Medical Risk in the Prediction of Infant Neurodevelopment

The current study examines the association between early father involvement and infant neurodevelopment, and whether neonatal medical risk moderates this association. Data from approximately 6000 fathers and their children were obtained from the Early Childhood Longitudinal Study: Birth Cohort (ECLS-B). Hierarchical regression was employed to analyze the data. The findings reveal that the association between early father involvement and infant neurodevelopment is contingent on both the timing of involvement (i.e., prenatal/perinatal or infancy) and offspring medical status at birth. The neurodevelopment of medically at-risk neonates was enhanced when fathers were involved during the gestational period and at the time of their birth. This relationship was not detected, however, in the case of infants who did not experience medical risks as neonates. Neonatal medical risk appears to be an important moderating factor in the link between father involvement during pregnancy and childbirth and infant neurodevelopment. Practitioners should continue to make efforts to involve fathers during gestation and childbirth. The findings of the present study suggest that doing so may protect against neurodevelopmental delays in neonates with medical risks.

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.