Do intrauterine or genetic influences explain the foetal origins of chronic disease? A novel experimental method for disentangling effects

Annual Research Review: Towards a deeper understanding of nature and nurture: combining family-based quasi-experimental methods with genomic data

Distinguishing between the effects of nature and nurture constitutes a major research goal for those interested in understanding human development. It is known, for example, that many parent traits predict mental health outcomes in children, but the causal processes underlying such associations are often unclear. Family-based quasi-experimental designs such as sibling comparison, adoption and extended family studies have been used for decades to distinguish the genetic transmission of risk from the environmental effects family members potentially have on one another. Recently, these designs have been combined with genomic data, and this combination is fuelling a range of exciting methodological advances. In this review we explore these advances - highlighting the ways in which they have been applied to date and considering what they are likely to teach us in the coming years about the aetiology and intergenerational transmission of psychopathology.

Using genetic designs to identify likely causal environmental contributions to psychopathology

The multifactorial nature of psychopathology, whereby both genetic and environmental factors contribute risk, has long been established. In this paper, we provide an update on genetically informative designs that are utilized to disentangle genetic and environmental contributions to psychopathology. We provide a brief reminder of quantitative behavioral genetic research designs that have been used to identify potentially causal environmental processes, accounting for genetic contributions. We also provide an overview of recent molecular genetic approaches that utilize genome-wide association study data which are increasingly being applied to questions relevant to psychopathology research. While genetically informative designs typically have been applied to investigate the origins of psychopathology, we highlight how these approaches can also be used to elucidate potential causal environmental processes that contribute to developmental course and outcomes. We highlight the need to use genetically sensitive designs that align with intervention and prevention science efforts, by considering strengths-based environments to investigate how positive environments can mitigate risk and promote children's strengths.

Systematic Review and Meta-analysis of Genetically Informed Research: Associations Between Parent Anxiety and Offspring Internalizing Problems

OBJECTIVE

Parent anxiety is associated with offspring internalizing problems (emotional problems related to anxiety and depression). This may reflect causal processes, whereby exposure to parent anxiety directly influences offspring internalizing (and/or vice versa). However, parent-offspring associations could also be attributable to their genetic relatedness. A systematic review and meta-analysis were conducted to investigate whether exposure to parent anxiety is associated with offspring internalizing after controlling for genetic relatedness.

METHOD

A literature search across 5 databases identified 429 unique records. Publications were retained if they used a quasi-experimental design in a general population sample to control for participant relatedness in associations between parent anxiety and offspring internalizing outcomes. Publications were excluded if they involved an experimental exposure or intervention. Studies of prenatal and postnatal anxiety exposure were meta-analyzed separately. Pearson's correlation coefficient estimates (r) were pooled using multilevel random-effects models.

RESULTS

Eight publications were retained. Data were drawn from 4 population cohorts, each unique to a quasi-experimental design: adoption, sibling-comparison, children-of-twins or in vitro fertilization. Cohorts were located in northern Europe or America. Families were predominantly of European ancestry. Three publications (Nfamilies >11,700; offspring age range, 0.5-10 years) showed no association between prenatal anxiety exposure and offspring internalizing outcomes after accounting for participant relatedness (r = .04; 95% CI: -.07, .14). Six publications (Nfamilies >12,700; offspring age range, 0.75-22 years) showed a small but significant association between concurrent symptoms in parents and offspring after accounting for participant relatedness (r = .13; 95% CI: .04, .21).

CONCLUSION

Initial literature, derived from homogeneous populations, suggests that prenatal anxiety exposure does not cause offspring internalizing outcomes. However, postnatal anxiety exposure may be causally associated with concurrent offspring internalizing via nongenetic pathways. Longitudinal stability, child-to-parent effects, and the role of moderators and methodological biases require attention.

Maternal Prenatal Smoking and Autism Spectrum Disorder in Offspring: A California Statewide Cohort and Sibling Study

We examined associations between maternal smoking and autism spectrum disorder (ASD) in children in a statewide population-based cohort and sibling-comparison design using California birth records (n = 2,015,104) with information on maternal smoking, demographic factors, and pregnancy (2007-2010). ASD cases (n = 11,722) were identified through California Department of Developmental Services records with diagnoses based on the Diagnostic and Statistical Manual of Mental Disorders-IV-TR. We estimated odds ratios for ASD with and without intellectual disability in the full cohort using logistic regression and in a sibling comparison using conditional logistic regression. In the full cohort, the adjusted odds ratio for ASD and maternal smoking 3 months before/during pregnancy compared with nonsmoking was 1.15 (95% confidence interval (CI): 1.04, 1.26), and it was similar in cases with (odds ratio = 1.12, 95% CI: 0.84, 1.49) and without intellectual disability (odds ratio = 1.15, 95% CI: 1.04, 1.27). Heavy prenatal smoking (≥20 cigarettes/day in any trimester) was related to an odds ratio of 1.55 (95% CI: 1.21, 1.98). In the sibling comparison, the odds ratio for heavy smoking was similarly elevated but the confidence interval was wide. Our findings are consistent with an increased risk for ASD in offspring of mothers who smoked ≥20 cigarettes/day during pregnancy; associations with lighter smoking were weaker.

Family-Based Designs that Disentangle Inherited Factors from Pre- and Postnatal Environmental Exposures: In Vitro Fertilization, Discordant Sibling Pairs, Maternal versus Paternal Comparisons, and Adoption Designs

Identifying environmental risk and protective exposures that have causal effects on health is an important scientific goal. Many environmental exposures are nonrandomly allocated and influenced by dispositional factors including inherited ones. We review family-based designs that can separate the influence of environmental exposures from inherited influences shared between parent and offspring. We focus on prenatal exposures. We highlight that the family-based designs that can separate the prenatal environment from inherited confounds are different to those that are able to pull apart later-life environmental exposures from inherited confounds. We provide a brief review of the literature on maternal smoking during pregnancy and offspring attention-deficit/hyperactivity disorder (ADHD) and conduct problems; these inconsistencies in the literature make a review useful and this illustrates that results of family-based genetically informed studies are inconsistent with a causal interpretation for this exposure and these two offspring outcomes.

Outcomes of pregnancies using donor sperm compared with those using partner sperm: systematic review and meta-analysis

BACKGROUND

Registry data from the Human Fertilisation and Embryology Authority (HFEA) show an increase of 40% in IUI and 377% in IVF cases using donor sperm between 2006 and 2016.

OBJECTIVE AND RATIONALE

The objective of this study was to establish whether pregnancies conceived using donor sperm are at higher risk of obstetric and perinatal complications than those conceived with partner sperm. As more treatments are being carried out using donor sperm, attention is being given to obstetric and perinatal outcomes, as events in utero and at delivery have implications for long-term health. There is a need to know if there is any difference in the outcomes of pregnancies between those conceived using donor versus partner sperm in order to adequately inform and counsel couples.

SEARCH METHODS

We performed a systematic review and meta-analysis of the outcomes of pregnancies conceived using donor sperm compared with partner sperm. Searches were performed in the OVID MEDLINE, OVID Embase, CENTRAL and CINAHL databases, including all studies published before 11 February 2019. The search strategy involved search terms for pregnancy, infant, donor sperm, heterologous artificial insemination, donor gametes, pregnancy outcomes and perinatal outcomes. Studies were included if they assessed pregnancies conceived by any method using, or infants born from, donor sperm compared with partner sperm and described early pregnancy, obstetric or perinatal outcomes. The Downs and Black tool was used for quality and bias assessment of studies.

OUTCOMES

Of 3391 studies identified from the search, 37 studies were included in the review and 36 were included in the meta-analysis. For pregnancies conceived with donor sperm, versus partner sperm, there was an increase in the relative risk (RR) (95% CI) of combined hypertensive disorders of pregnancy: 1.44 (1.17-1.78), pre-eclampsia: 1.49 (1.05-2.09) and small for gestational age (SGA): 1.42 (1.17-1.79) but a reduced risk of ectopic pregnancy: 0.69 (0.48-0.98). There was no difference in the overall RR (95% CI) of miscarriage: 0.94 (0.80-1.11), gestational diabetes: 1.49 (0.62-3.59), pregnancy-induced hypertension (PIH): 1.24 (0.87-1.76), placental abruption: 0.65 (0.04-10.37), placenta praevia: 1.19 (0.64-2.21), preterm birth: 0.98 (0.88-1.08), low birth weight: 0.97 (0.82-1.15), high birthweight: 1.28 (0.94-1.73): large for gestational age (LGA): 1.01 (0.84-1.22), stillbirth: 1.23 (0.97-1.57), neonatal death: 0.79 (0.36-1.73) and congenital anomaly: 1.15 (0.86-1.53).

WIDER IMPLICATIONS

The majority of our findings are reassuring, except for the mild increased risk of hypertensive disorders of pregnancy and SGA in pregnancies resulting from donor sperm. However, the evidence for this is limited and should be interpreted with caution because the evidence was based on observational studies which varied in their quality and risk of bias. Further high-quality population-based studies reporting obstetric outcomes in detail are required to confirm these findings.

Do natural experiments have an important future in the study of mental disorders?

There is an enormous interest in identifying the causes of psychiatric disorders but there are considerable challenges in identifying which risks are genuinely causal. Traditionally risk factors have been inferred from observational designs. However, association with psychiatric outcome does not equate to causation. There are a number of threats that clinicians and researchers face in making causal inferences from traditional observational designs because adversities or exposures are not randomly allocated to individuals. Natural experiments provide an alternative strategy to randomized controlled trials as they take advantage of situations whereby links between exposure and other variables are separated by naturally occurring events or situations. In this review, we describe a growing range of different types of natural experiment and highlight that there is a greater confidence about findings where there is a convergence of findings across different designs. For example, exposure to hostile parenting is consistently found to be associated with conduct problems using different natural experiment designs providing support for this being a causal risk factor. Different genetically informative designs have repeatedly found that exposure to negative life events and being bullied are linked to later depression. However, for exposure to prenatal cigarette smoking, while findings from natural experiment designs are consistent with a causal effect on offspring lower birth weight, they do not support the hypothesis that intra-uterine cigarette smoking has a causal effect on attention-deficit/hyperactivity disorder and conduct problems and emerging findings highlight caution about inferring causal effects on bipolar disorder and schizophrenia.

Maternal psychological distress during pregnancy and childhood health outcomes: a narrative review

Maternal psychological distress is common in pregnancy and may influence the risk of adverse outcomes in children. Psychological distress may cause a suboptimal intrauterine environment leading to growth and developmental adaptations of the fetus and child. In this narrative review, we examined the influence of maternal psychological distress during pregnancy on fetal outcomes and child cardiometabolic, respiratory, atopic and neurodevelopment-related health outcomes. We discussed these findings from an epidemiological and life course perspective and provided recommendations for future studies. The literature in the field of maternal psychological distress and child health outcomes is extensive and shows that exposure to stress during pregnancy is associated with multiple adverse child health outcomes. Because maternal psychological distress is an important and potential modifiable factor during pregnancy, it should be a target for prevention strategies in order to optimize fetal and child health. Future studies should use innovative designs and strategies in order to address the issue of causality.

Identifying the contribution of prenatal risk factors to offspring development and psychopathology: What designs to use and a critique of literature on maternal smoking and stress in pregnancy

Identifying prenatal environmental factors that have genuinely causal effects on psychopathology is an important research priority, but it is crucial to select an appropriate research design. In this review we explain why and what sorts of designs are preferable and focus on genetically informed/sensitive designs. In the field of developmental psychopathology, causal inferences about prenatal risks have not always been based on evidence generated from appropriate designs. We focus on reported links between maternal smoking during pregnancy and offspring attention-deficit/hyperactivity disorder or conduct problems. Undertaking a systematic review of findings from genetically informed designs and “triangulating” evidence from studies with different patterns of bias, we conclude that at present findings suggest it is unlikely that there is a substantial causal effect of maternal smoking in pregnancy on either attention-deficit/hyperactivity disorder or conduct problems. In contrast, for offspring birth weight (which serves as a positive control) findings strongly support a negative causal effect of maternal smoking in pregnancy. For maternal pregnancy stress, too few studies use genetically sensitive designs to draw firm conclusions, but continuity with postnatal stress seems important. We highlight the importance of moving beyond observational designs, for systematic evaluation of the breadth of available evidence and choosing innovative designs. We conclude that a broader set of prenatal risk factors should be examined, including those relevant in low- and middle-income contexts. Future directions include a greater use of molecular genetically informed designs such as Mendelian randomization to test causal hypotheses about prenatal exposure and offspring outcome.

Pregnancy risk factors in relation to oppositional-defiant and conduct disorder symptoms in the Avon Longitudinal Study of Parents and Children

BACKGROUND

Pregnancy factors have been implicated in offspring oppositional-defiant disorder (ODD) and conduct disorder (CD) symptoms. Literature still holds notable limitations, such as studying only a restricted set of pregnancy factors, use of screening questionnaires which assess broadly defined outcome measures, and lack of control for disruptive behavior comorbidity and genetic confounds. We aimed to address these gaps by prospectively studying a broad range of pregnancy factors in relation to both offspring ODD and CD symptomatology in the Avon Longitudinal Study of Parent and Children.

METHODS

Outcomes were ODD and CD symptom scores at age 7;9 years using the Development and Well-Being Assessment interview. We analyzed maternal (N ≈ 6300) and teacher ratings (N ≈ 4400) of ODD and CD scores separately using negative binomial regression in multivariable models. Control variables included comorbid attention-deficit/hyperactivity disorder symptoms, ODD or CD symptoms as appropriate, and genetic risk scores based on an independent CD genome-wide association study.

RESULTS

Higher ODD symptom scores were linked to paracetamol use (IRR = 1.24 [98.3% confidence interval 1.05-1.47], P = 0.002, teacher ratings) and life events stress (IRR = 1.22 [1.07-1.39], P = 0.002, maternal ratings) during pregnancy. Higher CD symptom scores were linked to maternal smoking (IRR = 1.33 [1.18-1.51], P < 0.001, maternal ratings), life events stress (IRR = 1.24 [1.11-1.38], P < 0.001, maternal ratings) and depressive symptoms (IRR = 1.14 [1.01-1.30], P = 0.006, maternal ratings) during pregnancy.

CONCLUSIONS

Common and potentially preventable pregnancy risk factors were independently related to both offspring ODD and CD symptomatology in children from the general population. Future studies should further address genetic confounds and confounding by environmental factors later in life.

Naturalistic Experimental Designs as Tools for Understanding the Role of Genes and the Environment in Prevention Research

Before genetic approaches were applied in experimental studies with human populations, they were used by animal and plant breeders to observe, and experimentally manipulate, the role of genes and environment on specific phenotypic or behavioral outcomes. For obvious ethical reasons, the same level of experimental control is not possible in human populations. Nonetheless, there are natural experimental designs in human populations that can serve as logical extensions of the rigorous quantitative genetic experimental designs used by animal and plant researchers. Applying concepts such as cross-fostering and common garden rearing approaches from the life science discipline, we describe human designs that can serve as naturalistic proxies for the controlled quantitative genetic experiments facilitated in life sciences research. We present the prevention relevance of three such human designs: (1) children adopted at birth by parents to whom they are not genetically related (common garden approach); (2) sibling designs where one sibling is reared from birth with unrelated adoptive parents and the other sibling is reared from birth by the biological mother of the sibling pair (cross-fostering approach); and (3) in vitro fertilization designs, including egg donation, sperm donation, embryo donation, and surrogacy (prenatal cross-fostering approach). Each of these designs allows for differentiation of the effects of the prenatal and/or postnatal rearing environment from effects of genes shared between parent and child in naturalistic ways that can inform prevention efforts. Example findings from each design type are provided and conclusions drawn about the relevance of naturalistic genetic designs to prevention science.

Cross-fostering: Elucidating the effects of gene×environment interactions on phenotypic development

Cross-fostering of litters from soon after birth until weaning is a valuable tool to study the ways in which gene×environment interactions program the development of neural, physiological and behavioral characteristics of mammalian species. In laboratory mice and rats, the primary focus of this review, cross-fostering of litters between mothers of different strains or treatment groups (intraspecific) or between mothers of different species (interspecific) has been conducted over the past 9 decades. Areas of particular interest have included maternal effects on emotionality, social preferences, responses to stressful stimulation, nutrition and growth, blood pressure regulation, and epigenetic effects on brain development and behavior. Results from these areas of research highlight the critical role of the postnatal maternal environment in programming the development of offspring phenotypic characteristics. In addition, experimental paradigms that have included cross-fostering have permitted investigators to tease apart prenatal versus postnatal effects of various treatments on offspring development and behavior.

A meta-analysis of sperm donation offspring health outcomes

Although the use of donor sperm as a treatment modality for male infertility has become common place, the health outcomes for those conceived has been poorly studied. A structured search of the literature using PubMed, EMBASE and Cochrane Reviews was performed to investigate the health outcomes of offspring conceived from donor sperm. Eight studies were eligible and included in the review, and of these, three were included in a meta-analysis. Meta-analysis of clinical outcomes showed that donor sperm neonates are not at increased risk of being born of low birth weight (<2500 g), preterm (<37 weeks) or with increased incidences of birth defects, than spontaneously conceived neonates.

Explaining risk for suicidal ideation in adolescent offspring of mothers with depression

BACKGROUND

It is well-established that offspring of depressed mothers are at increased risk for suicidal ideation. However, pathways involved in the transmission of risk for suicidal ideation from depressed mothers to offspring are poorly understood. The aim of this study was to examine the contribution of potential mediators of this association, including maternal suicide attempt, offspring psychiatric disorder and the parent-child relationship.

METHOD

Data were utilized from a population-based birth cohort (ALSPAC). Three distinct classes of maternal depression symptoms across the first 11 years of the child's life had already been identified (minimal, moderate, chronic-severe). Offspring suicidal ideation was assessed at age 16 years. Data were analysed using structural equation modelling.

RESULTS

There was evidence for increased risk of suicidal ideation in offspring of mothers with chronic-severe depression symptoms compared to offspring of mothers with minimal symptoms (odds ratio 3.04, 95% confidence interval 2.19-4.21). The majority of this association was explained through maternal suicide attempt and offspring psychiatric disorder. There was also evidence for an independent indirect effect via the parent-child relationship in middle childhood. There was no longer evidence of a direct effect of maternal depression on offspring suicidal ideation after accounting for all three mediators. The pattern of results was similar when examining mechanisms for maternal moderate depression symptoms.

CONCLUSIONS

Findings highlight that suicide prevention efforts in offspring of depressed mothers should be particularly targeted at both offspring with a psychiatric disorder and offspring whose mothers have made a suicide attempt. Interventions aimed at improving the parent-child relationship may also be beneficial.

A meta-analysis of neonatal health outcomes from oocyte donation

Donated oocytes are a treatment modality for female infertility which is also associated with increased risks of preeclampsia. Subsequently it is important to evaluate if there is concomitant increased risks for adverse neonatal events in donated oocyte neonates. A structured search of the literature using PubMed, EMBASE and Cochrane Reviews was performed to investigate the perinatal health outcomes of offspring conceived from donor oocytes compared with autologous oocytes. Meta-analysis was performed on comparable outcomes data. Twenty-eight studies were eligible and included in the review, and of these, 23 were included in a meta-analysis. Donor oocyte neonates are at increased risk of being born with low birth weight (<2500 g) [risk ratio (RR): 1.18, 95% confidence interval (CI): 1.14–1.22, P-value (P)<0.00001], very low birth weight (<1500 g) (RR: 1.24, CI: 1.15–1.35, P<0.00001), preterm (<37 weeks) (RR: 1.26, CI: 1.23–1.30, P<0.00001), of lower gestational age (mean difference −0.3 weeks, CI: −0.35 weeks to −0.25 weeks, P<0.00001), and preterm with low birth weight (RR: 1.24, CI: 1.19–1.29, P<0.00001), when compared with autologous oocyte neonates. Conversely, low birth weight outcomes were improved in term donor oocyte neonates (RR: 0.86, CI: 0.8–0.93, P=0.0003). These negative outcomes remained significant when controlling for multiple deliveries. The donor oocyte risk rates are higher than those found in general ART outcomes, are important considerations for the counselling of infertile patients and may also influence the long term health of the offspring.

Translational Epidemiologic Approaches to Understanding the Consequences of Early-Life Exposures

Prominent developmental theories posit a causal link between early-life exposures and later functioning. Yet, observed associations with early exposures may not reflect causal effects because of genetic and environmental confounding. The current manuscript describes how a systematic series of epidemiologic analyses that combine several genetically-informative designs and statistical approaches can help distinguish between competing theories. In particular, the manuscript details how combining the use of measured covariates with sibling-comparisons, cousin-comparisons, and additional designs can help elucidate the sources of covariation between early-life exposures and later outcomes, including the roles of (a) factors that are not shared in families, including a potential causal effect of the exposure; (b) carryover effects from the exposure of one child to the next; and (c) familial confounding. We also describe key assumptions and how they can be critically evaluated. Furthermore, we outline how subsequent analyses, including effect decomposition with respect to measured, plausible mediators, and quantitative genetic models can help further specify the underlying processes that account for the associations between early-life exposures and offspring outcomes.

Separating Family-Level and Direct Exposure Effects of Smoking During Pregnancy on Offspring Externalizing Symptoms: Bridging the Behavior Genetic and Behavior Teratologic Divide

Maternal smoking during pregnancy (MSDP) has been robustly associated with externalizing problems and their developmental precursors in offspring in studies using behavioral teratologic designs (Wakschlag et al., Am J Public Health 92(6):966-974, 2002; Espy et al., Dev Psychol 47(1):153-169, 2011). In contrast, the use of behavior genetic approaches has shown that the effects commonly attributed to MSDP can be explained by family-level variables (D'Onofrio et al., Dev Psychopathol 20(01):139-164, 2008). Reconciling these conflicting findings requires integration of these study designs. We utilize longitudinal data on a preschool proband and his/her sibling from the Midwest Infant Development Study-Preschool (MIDS-P) to test for teratologic and family level effects of MSDP. We find considerable variation in prenatal smoking patterns both within and across pregnancies within families, indicating that binary smoking measures are not sufficiently capturing exposure. Structural equation models indicate that both conduct disorder and oppositional defiant disorder symptoms showed unique effects of MSDP over and above family level effects. Blending high quality exposure measurement with a within-family design suggests that it is premature to foreclose the possibility of a teratologic effect of MSDP on externalizing problems. Implications and recommendations for future studies are discussed.

Raised by depressed parents: is it an environmental risk?

The mechanisms explaining how parental depression compromises healthy child development are complex and multifaceted, with genetic and environmental pathways intertwined. Reexamination of whether and how maternal and paternal depression serve as environmental risk factors is important because such an investigation can be helpful to identify modifiable mechanisms that are accessible to interventions. We review studies that have employed designs that isolate the effects of the environment from genetic influences, including adoption studies and children of twins studies. Findings indicate that maternal depression is an environmental risk factor for the emotional, behavioral, and neurobiological development of children. Although more studies are needed, preliminary findings suggest that paternal depression appears to be a weaker environmental risk as compared to maternal depression, at least during infancy and toddlerhood. Implications for theory and future research are discussed.

Testing the Developmental Origins of Health and Disease Hypothesis for Psychopathology Using Family-Based Quasi-Experimental Designs

The Developmental Origin of Health and Disease (DOHaD) hypothesis is a broad theoretical framework that emphasizes how early risk factors have a causal influence on psychopathology. Researchers have raised concerns about the causal interpretation of statistical associations between early risk factors and later psychopathology because most existing studies have been unable to rule out the possibility of environmental and genetic confounding. In this paper we illustrate how family-based quasi-experimental designs can test the DOHaD hypothesis by ruling out alternative hypotheses. We review the logic underlying sibling-comparison, co-twin control, offspring of siblings/twins, adoption, and in vitro fertilization designs. We then present results from studies using these designs focused on broad indices of fetal development (low birth weight and gestational age) and a particular teratogen, smoking during pregnancy. The results provide mixed support for the DOHaD hypothesis for psychopathology, illustrating the critical need to use design features that rule out unmeasured confounding.

Maternal smoking during pregnancy and offspring conduct problems: evidence from 3 independent genetically sensitive research designs

IMPORTANCE

Several studies report an association between maternal smoking during pregnancy and offspring conduct disorder. However, past research evidences difficulty in disaggregating prenatal environmental influences from genetic and postnatal environmental influences.

OBJECTIVE

To examine the relationship between maternal smoking during pregnancy and offspring conduct problems among children reared by genetically related mothers and genetically unrelated mothers.

DESIGN, SETTING, AND PARTICIPANTS

The following 3 studies using distinct but complementary research designs were used: The Christchurch Health and Development Study (a longitudinal cohort study that includes biological and adopted children), the Early Growth and Development Study (a longitudinal adoption-at-birth study), and the Cardiff IVF (In Vitro Fertilization) Study (an adoption-at-conception study among genetically related families and genetically unrelated families). Maternal smoking during pregnancy was measured as the mean number of cigarettes per day (0, 1-9, or 10) smoked during pregnancy. Possible covariates were controlled for in the analyses, including child sex, birth weight, race/ethnicity, placement age, and breastfeeding, as well as maternal education and maternal age at birth and family breakdown, parenting practices, and family socioeconomic status.

MAIN OUTCOMES AND MEASURE

Offspring conduct problems (age range, 4-10 years) reported by parents or teachers using the behavior rating scales by Rutter and Conners, the Child Behavior Checklist and the Children's Behavior Questionnaire Short Form, and the Strengths and Difficulties Questionnaire.

RESULTS

A significant association between maternal smoking during pregnancy and offspring conduct problems was observed among children reared by genetically related mothers and genetically unrelated mothers. Results from a meta-analysis affirmed this pattern of findings across pooled study samples.

CONCLUSIONS AND RELEVANCE

Findings across 3 studies using a complement of genetically sensitive research designs suggest that smoking during pregnancy is a prenatal risk factor for offspring conduct problems when controlling for specific perinatal and postnatal confounding factors.

Critical need for family-based, quasi-experimental designs in integrating genetic and social science research

Researchers have identified environmental risks that predict subsequent psychological and medical problems. Based on these correlational findings, researchers have developed and tested complex developmental models and have examined biological moderating factors (e.g., gene-environment interactions). In this context, we stress the critical need for researchers to use family-based, quasi-experimental designs when trying to integrate genetic and social science research involving environmental variables because these designs rigorously examine causal inferences by testing competing hypotheses. We argue that sibling comparison, offspring of twins or siblings, in vitro fertilization designs, and other genetically informed approaches play a unique role in bridging gaps between basic biological and social science research. We use studies on maternal smoking during pregnancy to exemplify these principles.

Prenatal adversity: a risk factor in borderline personality disorder?

BACKGROUND

Patients with borderline personality disorder (BPD) show a high prevalence of early adversity, such as childhood trauma. It has also been reported that prenatal adverse conditions, such as prenatal maternal stress, drug taking, tobacco smoking or medical complications, may be associated with an increased risk of mental disorders in the offspring. Prenatal adversity is investigated here for the first time as a potential risk factor in the diagnosis of BPD. Method A total of 100 patients with a DSM-IV diagnosis of BPD and 100 matched healthy controls underwent semi-structured interviews about the course of pregnancy, maternal stressors, birth complications and childhood trauma. Further information was obtained from the participants' mothers and from prenatal medical records.

RESULTS

Borderline patients were significantly more often exposed to adverse intrauterine conditions, such as prenatal tobacco exposure (p=0.004), medical complications (p=0.008), prenatal maternal traumatic stress (p=0.015), familial conflicts (p=0.004), low social support (p=0.004) and partnership problems during pregnancy (p=0.014). Logistic regression analyses revealed that the reported prenatal risk factors accounted for 25.7% of the variance in BPD. Prenatal tobacco exposure [odds ratio (OR) 3.37, 95% confidence interval (CI) 1.49-7.65, p=0.004] and medical complications (OR 2.87, 95% CI 1.29-6.38, p=0.010) emerged as important predictors. After controlling for childhood adversity and parental socio-economic status (SES), prenatal risk factors predicted relevant borderline subdomains, such as impulsivity, affective instability, identity disturbance, dissociation and severity of borderline symptoms.

CONCLUSIONS

This study provides evidence of an association between prenatal adversity and the diagnosis of BPD. Our findings suggest that prenatal adversity may constitute a potential risk factor in the pathogenesis of BPD.

Interparental conflict, parent psychopathology, hostile parenting, and child antisocial behavior: examining the role of maternal versus paternal influences using a novel genetically sensitive research design

Past research has linked interparental conflict, parent psychopathology, hostile parenting, and externalizing behavior problems in childhood. However, few studies have examined these relationships while simultaneously allowing the contribution of common genetic factors underlying associations between family- and parent-level variables on child psychopathology to be controlled. Using the attributes of a genetically sensitive in vitro fertilization research design, the present study examined associations among interparental conflict, parents' antisocial behavior problems, parents' anxiety symptoms, and hostile parenting on children's antisocial behavior problems among genetically related and genetically unrelated mother-child and father-child groupings. Path analyses revealed that for genetically related mothers, interparental conflict and maternal antisocial behavior indirectly influenced child antisocial behavior through mother-to-child hostility. For genetically unrelated mothers, effects were apparent only for maternal antisocial behavior on child antisocial behavior through mother-to-child hostility. For both genetically related and genetically unrelated fathers and children, interparental conflict and paternal antisocial behavior influenced child antisocial behavior through father-to-child hostility. Effects of parental anxiety symptoms on child antisocial behavior were apparent only for genetically related mothers and children. Results are discussed with respect to the relative role of passive genotype-environment correlation as a possible confounding factor underlying family process influences on childhood psychopathology.

The epigenetics of maternal cigarette smoking during pregnancy and effects on child development

The period of in utero development is one of the most critical windows during which adverse intrauterine conditions and exposures can influence the growth and development of the fetus as well as the child's future postnatal health and behavior. Maternal cigarette smoking during pregnancy remains a relatively common but nonetheless hazardous in utero exposure. Previous studies have associated prenatal smoke exposure with reduced birth weight, poor developmental and psychological outcomes, and increased risk for diseases and behavioral disorders later in life. Researchers are now learning that many of the mechanisms whereby maternal smoke exposure may affect key pathways crucial for proper fetal growth and development are epigenetic in nature. Maternal cigarette smoking during pregnancy has been associated with altered DNA methylation and dysregulated expression of microRNA, but a deeper understanding of the epigenetics of maternal cigarette smoking during pregnancy as well as how these epigenetic changes may affect later health and behavior remain to be elucidated. This article seeks to explore many of the previously described epigenetic alterations associated with maternal cigarette smoking during pregnancy and assess how such changes may have consequences for both fetal growth and development, as well as later child health, behavior, and well-being. We also outline future directions for this new and exciting field of research.

Is maternal smoking during pregnancy a causal environmental risk factor for adolescent antisocial behavior? Testing etiological theories and assumptions

BACKGROUND

Although many studies indicate that maternal smoking during pregnancy (SDP) is correlated with later offspring antisocial behavior (ASB), recent quasi-experimental studies suggest that background familial factors confound the association. The present study sought to test alternative etiological hypotheses using multiple indices of adolescent ASB, comparing differentially exposed siblings, and testing assumptions in the sibling-comparison design.

METHOD

The study examined the association between maternal SDP and adolescent-reported ASB, criminal convictions and membership in a group of individuals with early-starting and chronic ASB among 6066 offspring of women from the National Longitudinal Survey of Youth, a representative sample of women in the USA. The analyses controlled for statistical covariates and examined associations while comparing differentially exposed siblings.

RESULTS

At the population level, each additional pack of cigarettes per day predicted greater mean adolescent-reported ASB symptoms [ratio of means 1.15, 95% confidence interval (CI) 1.08-1.22], odds of being in the top 10% of ASB [odds ratio (OR) 1.34, 95% CI 1.10-1.65], hazard of a criminal conviction [hazard ratio (HR) 1.51, 95% CI 1.34-1.68] and odds of chronic ASB (OR 1.57, 95% CI 1.25-1.99). SDP robustly predicted most assessments of ASB while controlling for measured covariates. When siblings exposed to differing levels of SDP were compared, however, all of the associations were attenuated and were not statistically significant: adolescent-reported mean ASB (ratio of means 0.86, 95% CI 0.74-1.01), high ASB (OR 0.67, 95% CI 0.41-1.12), criminal conviction (HR 0.98, 95% CI 0.66-1.44) and chronic ASB (OR 0.80, 95% CI 0.46-1.38).

CONCLUSIONS

The results strongly suggest that familial factors account for the correlation between SDP and offspring adolescent ASB, rather than a putative causal environmental influence of SDP.

Analysis of genetic interactions involving maternal and offspring genotypes at different Loci: power simulation and application to testicular cancer

The analyses of genetic interaction between maternal and offspring genotypes are usually conducted considering a single locus. Here, we propose testing maternal × offspring (M×O) and maternal × maternal (M×M) genotype interactions involving two unlinked loci. We reformulate the log-linear approach of analyzing cases and their parents (family trios) to accommodate two loci, fit fuller models to avoid confounding in a first analysis step and propose that the model be reduced to the most prominent effects in a second step. We conduct extensive simulations to assess the validity and power of this approach under various model assumptions. We show that the approach is valid and has good power to detect M×O and M×M interactions. For example, the power to detect a dominant interaction relative risk of 1.5 (both M×O and M×M) is 70% with 300 trios and approaches 100% with 1,000 trios. Unlike the main effects, M×O and M×M interactions are conditionally independent of mating types, and consequently, their power is not affected by missing paternal genotypes. When applied to single-locus M×O interaction, our method is as powerful as other existing methods. Applying the method to testicular cancer, we found a nominally significant M×M interaction between single nucleotide polymorphisms from C-Kit Ligand (KITLG) and Sex Hormone Binding Globulin (SHBG) using 210 families (relative risk 2.2, P = 0.03). This finding supports a role of maternal hormones in offspring testicular cancer and warrants confirmation in a larger dataset.

Short- and long-term reproductive effects of prenatal and lactational growth restriction caused by maternal diabetes in male rats

BACKGROUND

A suboptimal intrauterine environment may have a detrimental effect on gonadal development and thereby increases the risk for reproductive disorders and infertility in adult life. Here, we used uncontrolled maternal diabetes as a model to provoke pre- and perinatal growth restriction and evaluate the sexual development of rat male offspring.

METHODS

Maternal diabetes was induced in the dams through administration of a single i.v. dose of 40 mg/kg streptozotocin, 7 days before mating. Female rats presenting glycemic levels above 200 mg/dL after the induction were selected for the experiment. The male offspring was analyzed at different phases of sexual development, i.e., peripuberty, postpuberty and adulthood.

RESULTS

Body weight and blood glucose levels of pups, on the third postnatal day, were lower in the offspring of diabetic dams compared to controls. Maternal diabetes also provoked delayed testicular descent and preputial separation. In the offspring of diabetic dams the weight of reproductive organs at 40, 60 and 90 days-old was lower, as well as sperm reserves and sperm transit time through the epididymis. However the plasma testosterone levels were not different among experimental groups.

CONCLUSIONS

It is difficult to isolate the effects directly from diabetes and those from IUGR. Although the exposure to hyperglycemic environment during prenatal life and lactation delayed the onset of puberty in male rats, the IUGR, in the studied model, did not influenced the structural organization of the male gonads of the offspring at any point during sexual development. However the decrease in sperm reserves in epididymal cauda and the acceleration in sperm transit time in this portion of epididymis may lead to an impairment of sperm quality and fertility potential in these animals. Additional studies are needed in attempt to investigate the fertility of animals with intrauterine growth restriction by maternal diabetes and possible multigenerational effects.

Using a genetically informative design to examine the relationship between breastfeeding and childhood conduct problems

A number of public health interventions aimed at increasing the uptake of breastfeeding are in place in the United States and other Western countries. While the physical health and nutritional benefits of breastfeeding for the mother and child are relatively well established, the evidence for psychological effects is less clear. This study aimed to examine whether there is an association between breastfeeding and later conduct problems in children. It also considered the extent to which any relationship is attributable to maternally-provided inherited characteristics that influence both likelihood of breastfeeding and child conduct problems. A prenatal cross-fostering design with a sample of 870 families with a child aged 4-11 years was used. Mothers were genetically related or unrelated to their child as a result of assisted reproductive technologies. The relationship between breastfeeding and conduct problems was assessed while controlling for theorised measured confounders by multivariate regression (e.g. maternal smoking, education, and antisocial behaviour), and for unmeasured inherited factors by testing associations separately for related and unrelated mother-child pairs. Breastfeeding was associated with lower levels of conduct disorder symptoms in offspring in middle childhood. Breastfeeding was associated with lower levels of conduct problems even after controlling for observed confounders in the genetically related group, but not in the genetically unrelated group. In contrast, maternal antisocial behaviour showed robust associations with child conduct problems after controlling for measured and inherited confounders. These findings highlight the importance of using genetically sensitive designs in order to test causal environmental influences.

Dissecting prenatal, postnatal, and inherited effects: ART and design

With the failure of common variants alone to explain the bulk of trait heritability, it becomes more important to understand the contribution of maternally inherited effects, prenatal effects, and postnatal environmental effects. These effects can be disentangled by studying families containing children conceived by assisted reproductive technologies (ART). We propose and develop a model that is an extension of the variance component model commonly used in pedigree analysis. Our model is flexible enough to allow any number of family members and degrees of relationship; thus, researchers can use both small and extended families simultaneously. Simulations demonstrate that our method has appropriate statistical properties and is robust to model misspecification and accurate in the presence of missing data. Most importantly, our method is able to disentangle maternally inherited effects from prenatal effects, which are confounded in traditional family studies. Our analyses also provide guidance to researchers designing studies that will use ART families to clarify genetic and environmental factors underlying traits.

Familial transmission of depression and antisocial behavior symptoms: disentangling the contribution of inherited and environmental factors and testing the mediating role of parenting

BACKGROUND

Genetic and environmental influences on child psychopathology have been studied extensively through twin and adoption designs. We offer a novel methodology to examine genetic and environmental influences on the intergenerational transmission of psychopathology using a sample of parents and children conceived through in vitro fertilization (IVF).

METHOD

The sample included families with children born through IVF methods, who varied as to whether the child was genetically related or unrelated to the rearing mother and father (mother genetically related, n=434; mother genetically unrelated, n=127; father genetically related, n=403; father genetically unrelated, n=156). Using standardized questionnaires, mothers and fathers respectively reported on their own psychopathology (depression, aggression), their parenting behavior toward their child (warmth, hostility) and their child's psychopathology (depression, aggression). A cross-rater approach was used, where opposite parents reported on child symptoms (i.e. fathers reported on symptoms for the mother-child dyad, and vice versa).

RESULTS

For mother-child dyads, a direct association between mother depression and child depression was observed among genetically unrelated dyads, whereas a fully mediated path was observed among genetically related dyads through mother-to-child hostility and warmth. For father-child dyads, direct and mediated pathways were observed for genetically related father-child dyads. For aggression, the direct association between parent aggression and child aggression was fully mediated by parent-to-child hostility for both groups, indicating the role of parent-to-child hostility as a risk mechanism for transmission.

CONCLUSIONS

A differential pattern of genetic and environmental mediation underlying the intergenerational transmission of psychopathology was observed among genetically related and genetically unrelated father-child and mother-child dyads.

What are the causal effects of breastfeeding on IQ, obesity and blood pressure? Evidence from comparing high-income with middle-income cohorts

BACKGROUND

A novel approach is explored for improving causal inference in observational studies by comparing cohorts from high-income with low- or middle-income countries (LMIC), where confounding structures differ. This is applied to assessing causal effects of breastfeeding on child blood pressure (BP), body mass index (BMI) and intelligence quotient (IQ).

METHODS

Standardized approaches for assessing the confounding structure of breastfeeding by socio-economic position were applied to the British Avon Longitudinal Study of Parents and Children (ALSPAC) (N ≃ 5000) and Brazilian Pelotas 1993 cohorts (N ≃ 1000). This was used to improve causal inference regarding associations of breastfeeding with child BP, BMI and IQ. Analyses were extended to include results from a meta-analysis of five LMICs (N ≃ 10 000) and compared with a randomized trial of breastfeeding promotion. Findings Although higher socio-economic position was strongly associated with breastfeeding in ALSPAC, there was little such patterning in Pelotas. In ALSPAC, breastfeeding was associated with lower BP, lower BMI and higher IQ, adjusted for confounders, but in the directions expected if due to socioeconomic patterning. In contrast, in Pelotas, breastfeeding was not strongly associated with BP or BMI but was associated with higher IQ. Differences in associations observed between ALSPAC and the LMIC meta-analysis were in line with those observed between ALSPAC and Pelotas, but with robust evidence of heterogeneity detected between ALSPAC and the LMIC meta-analysis associations. Trial data supported the conclusions inferred by the cross-cohort comparisons, which provided evidence for causal effects on IQ but not for BP or BMI.

CONCLUSION

While reported associations of breastfeeding with child BP and BMI are likely to reflect residual confounding, breastfeeding may have causal effects on IQ. Comparing associations between populations with differing confounding structures can be used to improve causal inference in observational studies.

Genetics of childhood and adolescent depression: insights into etiological heterogeneity and challenges for future genomic research

There is heterogeneity between depression in childhood, adolescence and adulthood in terms of the gender composition of affected cases, prevalence, rates of recurrence and risk factors. This raises complex questions for refining the phenotype for molecular genetic studies of depression and the selection of appropriate proband groups. This article aims to provide a review of issues arising from family, twin and adoption studies of relevance to molecular genetic studies, and to summarize molecular genetic findings on childhood/adolescent depression. While retrospective studies of adults suggest greater familial aggregation among those with an earlier age of onset, prospective studies do not confirm this association. In fact, taken together, evidence from family and twin studies suggests that prepubertal depression is more strongly associated with psychosocial adversity, is less heritable and shows lower levels of continuity with adult depression than either adolescent or adult depression. Adolescent depressive symptoms and disorder show similar levels of heritability to depression in adult life, although there is only one twin study of adolescent depressive disorder, and heritability estimates of depressive symptoms vary widely between studies. This variability in heritability estimates is partly attributable to age and informant effects. Adoption studies and other intergenerational transmission designs show that the transmission of depression between parents and children involves genetic and environmental processes, with converging evidence that environmental processes are most important. Molecular genetic studies of childhood/adolescent depression have to date used a candidate gene approach and focused on genes already examined in adult studies. Prospective longitudinal studies of community and high-risk samples are needed to clarify issues of etiological heterogeneity in depression, and these should in turn inform the planning of molecular genetic studies.

Interaction of prenatal exposure to cigarettes and MAOA genotype in pathways to youth antisocial behavior

Genetic susceptibility to antisocial behavior may increase fetal sensitivity to prenatal exposure to cigarette smoke. Testing putative gene x exposure mechanisms requires precise measurement of exposure and outcomes. We tested whether a functional polymorphism in the gene encoding the enzyme monoamine oxidase A (MAOA) interacts with exposure to predict pathways to adolescent antisocial behavior. We assessed both clinical and information-processing outcomes. One hundred seventy-six adolescents and their mothers participated in a follow-up of a pregnancy cohort with well-characterized exposure. A sex-specific pattern of gene x exposure interaction was detected. Exposed boys with the low-activity MAOA 5' uVNTR (untranslated region variable number of tandem repeats) genotype were at increased risk for conduct disorder (CD) symptoms. In contrast, exposed girls with the high-activity MAOA uVNTR genotype were at increased risk for both CD symptoms and hostile attribution bias on a face-processing task. There was no evidence of a gene-environment correlation (rGE). Findings suggest that the MAOA uVNTR genotype, prenatal exposure to cigarettes and sex interact to predict antisocial behavior and related information-processing patterns. Future research to replicate and extend these findings should focus on elucidating how gene x exposure interactions may shape behavior through associated changes in brain function.

Estimating the relative contributions of maternal genetic, paternal genetic and intrauterine factors to offspring birth weight and head circumference

BACKGROUND

Genetic factors and the prenatal environment contribute to birth weight. However, very few types of study design can disentangle their relative contribution.

AIMS

To examine maternal genetic and intrauterine contributions to offspring birth weight and head circumference. To compare the contribution of maternal and paternal genetic effects.

STUDY DESIGN

Mothers and fathers were either genetically related or unrelated to their offspring who had been conceived by in vitro fertilization.

SUBJECTS

423 singleton full term offspring, of whom 262 were conceived via homologous IVF (both parents related), 66 via sperm donation (mother only related) and 95 via egg donation (father only related).

MEASURES

Maternal weight at antenatal booking, current weight and maternal height. Paternal current weight and height were all predictors. Infant birth weight and head circumference were outcomes.

RESULTS

Genetic relatedness was the main contributing factor between measures of parental weight and offspring birth weight as correlations were only significant when the parent was related to the child. However, there was a contribution of the intrauterine environment to the association between maternal height and both infant birth weight and infant head circumference as these were significant even when mothers were unrelated to their child.

CONCLUSIONS

Both maternal and paternal genes made contributions to infant birth weight. Maternal height appeared to index a contribution of the intrauterine environment to infant growth and gestational age. Results suggested a possible biological interaction between the intrauterine environment and maternal inherited characteristics which suppresses the influence of paternal genes.

The links between prenatal stress and offspring development and psychopathology: disentangling environmental and inherited influences

BACKGROUND

Exposure to prenatal stress is associated with later adverse health and adjustment outcomes. This is generally presumed to arise through early environmentally mediated programming effects on the foetus. However, associations could arise through factors that influence mothers' characteristics and behaviour during pregnancy which are inherited by offspring.

METHOD

A 'prenatal cross-fostering' design where pregnant mothers are related or unrelated to their child as a result of in vitro fertilization (IVF) was used to disentangle maternally inherited and environmental influences. If links between prenatal stress and offspring outcome are environmental, association should be observed in unrelated as well as related mother-child pairs. Offspring birth weight and gestational age as well as mental health were the outcomes assessed.

RESULTS

Associations between prenatal stress and offspring birth weight, gestational age and antisocial behaviour were seen in both related and unrelated mother-offspring pairs, consistent with there being environmental links. The association between prenatal stress and offspring anxiety in related and unrelated groups appeared to be due to current maternal anxiety/depression rather than prenatal stress. In contrast, the link between prenatal stress and offspring attention deficit hyperactivity disorder was only present in related mother-offspring pairs and therefore was attributable to inherited factors.

CONCLUSIONS

Genetically informative designs can be helpful in testing whether inherited factors contribute to the association between environmental risk factors and health outcomes. These results suggest that associations between prenatal stress and offspring outcomes could arise from inherited factors and post-natal environmental factors in addition to causal prenatal risk effects.

Prenatal smoking might not cause attention-deficit/hyperactivity disorder: evidence from a novel design

BACKGROUND

It is widely considered that exposure to maternal cigarette smoking in pregnancy has risk effects on offspring attention-deficit/hyperactivity disorder (ADHD). This view is supported by consistent observations of association. It is, however, impossible to be certain of adequate control for confounding factors with observational designs. We use a novel "natural experiment" design that separates prenatal environmental from alternative inherited effects.

METHODS

The design is based on offspring conceived with Assisted Reproductive Technologies recruited from 20 fertility clinics in the United Kingdom and United States who were: 1) genetically unrelated, and 2) related to the woman who underwent the pregnancy. If maternal smoking in pregnancy has true risk effects, association will be observed with ADHD regardless of whether mother and offspring are related or unrelated. Data were obtained from 815 families of children ages 4 years-11 years with parent questionnaires and antenatal records. Birth weight was used as a comparison outcome. The key outcome considered was child ADHD symptoms.

RESULTS

Association between smoking in pregnancy and lower birth weight was found in unrelated and related mother-offspring pairs, consistent with a true risk effect. However, for ADHD symptoms, the magnitude of association was significantly higher in the related pairs (beta = .102, p < .02) than in the unrelated pairs (beta= -.052, p > .10), suggesting inherited effects.

CONCLUSIONS

Our findings highlight the need to test causal hypotheses with genetically sensitive designs. Inherited confounds are not necessarily removed by statistical controls. The previously observed association between maternal smoking in pregnancy and ADHD might represent an inherited effect.

Fetal origins of mental health: evidence and mechanisms

The concept of fetal programming states that changes in the fetal environment during sensitive periods of organ development may cause long-lasting changes in the structure and functioning of these organs later in life and influence the risk for chronic diseases such as coronary heart disease and type 2 diabetes. Fetal growth is a summary marker of the fetal environment and is reflected by relatively easy-to-obtain measures of size at birth such as birth weight. In the last two decades, a body of evidence emerged linking fetal growth with behavioural and mental health outcomes later in life. Cognitive functioning and behavioural problems in childhood, in particular inattention/hyperactivity, have been shown to be inversely related to fetal growth. Although results are mixed, risk for personality disorders and schizophrenia seems to be linked with fetal growth and adversity, while the evidence for mood disorders is weak. Vulnerability for psychopathology may also be influenced by prenatal adversity. There is evidence for associations of fetal growth with temperament in childhood as well as stress reactivity and distress. The associations of fetal growth with mental health later in life are potentially caused by specific prenatal factors such as maternal smoking, alcohol, toxins/drugs, nutrition, psychosocial stress and infection during pregnancy. The mechanisms likely involve changes in neurodevelopment and in the set point of neuroendocrine systems, and there is evidence that prenatal adversity interacts with genetic and postnatal environmental factors. Future studies should examine the effects of specific prenatal factors and attempt to disentangle genetic and prenatal environmental effects.

Examining differences in psychological adjustment problems among children conceived by assisted reproductive technologies

The aim of this study was to examine whether there was variation in levels of psychological adjustment among children conceived through Assisted Reproductive Technologies using the parents’ gametes (homologous), sperm donation, egg donation, embryo donation and surrogacy. Information was provided by parents about the psychological functioning of 769 children aged 5 to 9 years who had been born using ART (from the five groups described). Comparisons were made between the different conception groups, to UK national norms and, for a sub-sample of multiple births, to an age-matched twin sample. No differences were found between the conception groups except that fathers from the egg donation group rated children higher in conduct problems compared to other ART groups. No effects were observed by ART treatment type (ICSI vs. IVF, GIFT and IUI). There was some evidence of lower conduct problems and prosocial behaviour among children conceived through homologous IVF compared to national norms. Taken together, however, consistent differences between groups and in comparison to naturally conceived children were not apparent for mother- or father-rated adjustment problems. Children conceived with assisted reproductive technologies, regardless of whether they are genetically related or unrelated to their parents or born by gestational surrogacy do not differ in their levels of psychological adjustment. Nor do they appear to be at greater risk of psychological adjustment problems in middle childhood compared to naturally conceived children.

Associations between maternal older age, family environment and parent and child wellbeing in families using assisted reproductive techniques to conceive

Maternal age effects on parenting and family outcomes are of increasing interest because of the demographic shift toward older maternal age at first birth. Maternal age is also of interest because of the greater use of assisted reproductive techniques (ART) to bypass age-related infertility in couples trying to conceive late in the reproductive life cycle of the woman. The aim of the present study was to investigate maternal age effects associated with delayed parenting by comparing families of mothers who gave birth at a younger (<31 years) or older (>38 years) age and to ascertain whether associations were linear associations by comparing these groups to women who had conceived in between these ages (i.e., >31 and <38 years). All children (4-11 year olds) were first-born and conceived using ART. Participants were recruited from one of 20 fertility clinics and mothers (n=642) and fathers (n=439) completed a postal questionnaire about demographic and reproductive characteristics, family environment as well as parent and child wellbeing. Our results demonstrate that parenthood via assisted conception later in the reproductive life cycle is not associated with a negative impact on child wellbeing. Despite maternal age-group differences on demographic (education, income) and reproductive characteristics (bleeding during pregnancy, caesarean rate, breast feeding), and parental warmth and depressive symptoms, child wellbeing was similar across mother age groups. We conclude that the parenting context is different for older mother families (more depressive symptoms in mothers and fathers, less expressed warmth in the couple) but that this difference is not associated with child wellbeing in early and middle childhood.

Disentangling prenatal and inherited influences in humans with an experimental design

Exposure to adversity in utero at a sensitive period of development can bring about physiological, structural, and metabolic changes in the fetus that affect later development and behavior. However, the link between prenatal environment and offspring outcomes could also arise and confound because of the relation between maternal and offspring genomes. As human studies cannot randomly assign offspring to prenatal conditions, it is difficult to test whether in utero events have true causal effects on offspring outcomes. We used an unusual approach to overcome this difficulty whereby pregnant mothers are either biologically unrelated or related to their child as a result of in vitro fertilization (IVF). In this sample, prenatal smoking reduces offspring birth weight in both unrelated and related offspring, consistent with effects arising through prenatal mechanisms independent of the relation between the maternal and offspring genomes. In contrast, the association between prenatal smoking and offspring antisocial behavior depended on inherited factors because association was only present in related mothers and offspring. The results demonstrate that this unusual prenatal cross-fostering design is feasible and informative for disentangling inherited and prenatal effects on human health and behavior. Disentangling these different effects is invaluable for pinpointing markers of prenatal adversity that have a causal effect on offspring outcomes. The origins of behavior and many common complex disorders may begin in early life, therefore this experimental design could pave the way for identifying prenatal factors that affect behavior in future generations.

Effects of bisphenol-A and other endocrine disruptors compared with abnormalities of schizophrenia: an endocrine-disruption theory of schizophrenia

In recent years, numerous substances have been identified as so-called "endocrine disruptors" because exposure to them results in disruption of normal endocrine function with possible adverse health outcomes. The pathologic and behavioral abnormalities attributed to exposure to endocrine disruptors like bisphenol-A (BPA) have been studied in animals. Mental conditions ranging from cognitive impairment to autism have been linked to BPA exposure by more than one investigation. Concurrent with these developments in BPA research, schizophrenia research has continued to find evidence of possible endocrine or neuroendocrine involvement in the disease. Sufficient information now exists for a comparison of the neurotoxicological and behavioral pathology associated with exposure to BPA and other endocrine disruptors to the abnormalities observed in schizophrenia. This review summarizes these findings and proposes a theory of endocrine disruption, like that observed from BPA exposure, as a pathway of schizophrenia pathogenesis. The review shows similarities exist between the effects of exposure to BPA and other related chemicals with schizophrenia. These similarities can be observed in 11 broad categories of abnormality: physical development, brain anatomy, cellular anatomy, hormone function, neurotransmitters and receptors, proteins and factors, processes and substances, immunology, sexual development, social behaviors or physiological responses, and other behaviors. Some of these similarities are sexually dimorphic and support theories that sexual dimorphisms may be important to schizophrenia pathogenesis. Research recommendations for further elaboration of the theory are proposed.

Intrauterine growth and infant temperamental difficulties: the Generation R Study

OBJECTIVE

To determine whether intrauterine growth trajectories are associated with temperamental difficulties in infancy.

METHOD

The Generation R Study is a population-based cohort study from fetal life onward. Size at different time points during gestation and growth trajectories, calculated on the basis of repeatedly measured fetal growth characteristics, were related to temperamental dimensions, assessed with the Infant Behavior Questionnaire-Revised, in 3,792 infants age 6 months.

RESULTS

Birth weight, adjusted for gestational age, was negatively associated with activity level and duration of orienting. These associations disappeared after additional adjustment for maternal height, age, educational level, and national origin. Similarly, the negative associations between intrauterine total body weight gain and falling reactivity and activity level diminished after correction for maternal and child characteristics. After full adjustment, reduced fetal weight gain was only related to prolonged duration of orienting. Children scored 0.38 (95% confidence interval 0.09-0.68) points higher on duration of orienting per SD decrease in total body weight gain from mid-pregnancy to birth.

CONCLUSIONS

After controlling for several genetic and socioeconomic status related factors, we found little indication of an association between intrauterine growth trajectories and temperamental difficulties in infants.