Prenatal Cotinine Levels and ADHD Among Offspring

Vaporized nicotine in utero results in reduced birthweight, increased locomotion, and decreased voluntary exercise, dependent on sex and diet in offspring

Rationale Clinical research has shown that prenatal exposure to nicotine may result in increased obesity risk later in life. Preclinical research has corroborated this finding, but few studies have investigated inhaled nicotine or the interaction with diet on obesity risk. Objective The aim of this study was to investigate the effects of prenatal nicotine exposure on both direct and indirect obesity measures, with both sex and diet as factors. Methods Pregnant rats were exposed to either vehicle or nicotine vapor (24 mg/mL or 59 mg/mL) throughout the entire gestational period. Offspring from each treatment group were given either a normal diet or a high fat diet starting at postnatal day 22. Caloric intake, body weight, spontaneous locomotion, sleep/wake activity, and voluntary exercise were measured throughout adolescence. Pregnancy weight gain and pup birthweights were collected to further measure developmental effects of prenatal nicotine exposure. Results Both maternal weight gain during pregnancy and pup weight at birth were decreased with prenatal nicotine exposure. Early adolescent males showed increased spontaneous activity in the open field following prenatal nicotine exposure compared to vehicle counterparts, particularly those given high-fat diet. Additionally, high dose nicotine prenatal treated males ran significantly less distance on the running wheel in late adolescence compared to vehicle counterparts, in the normal diet group only. Conclusion The results presented here show decreased birthweight, hyperactivity, and decreased voluntary exercise in adolescence following prenatal nicotine exposure in dose, sex, and diet dependent manners, which could lead to increased obesity risk in adulthood.

The causal impact of maternal smoking around birth on offspring ADHD: A two-sample Mendelian randomization study

BACKGROUND

The previous literature highlights a relationship between maternal smoking around birth (MSAB) and offspring attention-deficit/hyperactivity disorder (ADHD). These studies have focused on the causal effects of MSAB on offspring ADHD.

METHOD

A Mendelian randomization analysis was conducted using summary statistics. Data on MSAB were obtained from a recent study including 391,992 participants. ADHD data were obtained from six sources for 246,888 participants. The present study used five methods to examine the causal impact from outcomes on exposures. The inverse variance weighted (IVW) was the main method of analysis, while the other four methods were supplementary methods.

RESULT

The IVW revealed that MSAB was a risk factor for offspring ADHD (OR: 2.54; 95 % confidence interval [CI]: 1.61-4.00, p = 6.04 × 10-5). Concerning ADHD in both sexes, MSAB was associated with females (OR = 3.96, 95 % CI: 1.99-7.90, p = 8.98 × 10-5) and males (OR = 3.74, 95 % CI: 1.74-5.72, p = 1.48 × 10-4). In different diagnosis periods for ADHD, MSAB increased the risk of childhood (OR = 3.63, 95 % CI: 2.25-5.87, p = 1.31 × 10-7), late-diagnosed (OR = 2.99, 95 % CI: 1.74-5.14, p = 7.33 × 10-5), and persistent (OR = 4.77, 95 % CI: 1.88-12.14, p = 1.03 × 10-3) ADHD. The final analysis did not reveal heterogeneity.

CONCLUSIONS

A causal impact of MSAB on offspring ADHD was observed. These findings highlight the need for careful consideration of prenatal exposure (MSAB) during the assessment of offspring ADHD. Additionally, it can provide targeted guidance for prenatal interventions. Future studies should analyze the effects of different doses of maternal smoking on ADHD.

Molecular Mechanisms Underlying NMDARs Dysfunction and Their Role in ADHD Pathogenesis

Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders, although the aetiology of ADHD is not yet understood. One proposed theory for developing ADHD is N-methyl-D-aspartate receptors (NMDARs) dysfunction. NMDARs are involved in regulating synaptic plasticity and memory function in the brain. Abnormal expression or polymorphism of some genes associated with ADHD results in NMDAR dysfunction. Correspondingly, NMDAR malfunction in animal models results in ADHD-like symptoms, such as impulsivity and hyperactivity. Currently, there are no drugs for ADHD that specifically target NMDARs. However, NMDAR-stabilizing drugs have shown promise in improving ADHD symptoms with fewer side effects than the currently most widely used psychostimulant in ADHD treatment, methylphenidate. In this review, we outline the molecular and genetic basis of NMDAR malfunction and how it affects the course of ADHD. We also present new therapeutic options related to treating ADHD by targeting NMDAR.

Prenatal nicotine exposure during pregnancy results in adverse neurodevelopmental alterations and neurobehavioral deficits

Maternal tobacco use and nicotine exposure during pregnancy have been associated with adverse birth outcomes in infants and can lead to preventable pregnancy complications. Exposure to nicotine and other compounds in tobacco and electronic cigarettes (e-cigarettes) has been shown to increases the risk of miscarriage, prematurity, stillbirth, low birth weight, perinatal morbidity, and sudden infant death syndrome (SIDS). Additionally, recent data provided by clinical and pre-clinical research demonstrates that nicotine exposure during pregnancy may heighten the risk for adverse neurodevelopmental disorders such as Attention-Deficit Hyperactivity (ADHD), anxiety, and depression along with altering the infants underlying brain circuitry, response to neurotransmitters, and brain volume. In the United States, one in 14 women (7.2%) reported to have smoked cigarettes during their pregnancy with the global prevalence of smoking during pregnancy estimated to be 1.7%. Approximately 1.1% of women in the United States also reported to have used e-cigarettes during the last 3 months of pregnancy. Due to the large percentage of women utilizing nicotine products during pregnancy in the United States and globally, this review seeks to centralize pre-clinical and clinical studies focused on the neurobehavioral and neurodevelopmental complications associated with prenatal nicotine exposure (PNE) such as alterations to the hypothalamic-pituitary-adrenal (HPA) axis and brain regions such as the prefrontal cortex (PFC), ventral tegmental area (VTA), nucleus accumbens (NA), hippocampus, and caudate as well as changes to nAChR and cholinergic receptor signaling, long-term drug seeking behavior following PNE, and other related developmental disorders. Current literature analyzing the association between PNE and the risk for offspring developing schizophrenia, attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), anxiety, and obesity will also be discussed.

Associations between prenatal exposure to second hand smoke and infant self-regulation in a New York city longitudinal prospective birth cohort

BACKGROUND

Prenatal exposure to active or passive maternal smoking -also referred to as second hand smoke (SHS) exposure - are associated with externalizing behaviors, hyperactivity and attention deficit hyperactivity disorder, problems which derive in part from altered self-regulation.

OBJECTIVES

Determine the influence of prenatal SHS on infant self-regulation using direct measures of infant behavior in 99 mothers from the Fair Start birth cohort followed at the Columbia Center for Children's Environmental Health.

METHODS

Self-regulation was operationalized with self-contingency, the likelihood of maintaining/changing behavior from second-to-second, measured via split-screen video recordings of mothers playing with their 4-month infants. Mother and infant facial and vocal affect, gaze-on/-off partner, and mother touch were coded on a 1 s time-base. Third trimester prenatal SHS was assessed via self-report of a smoker in the home. Weighted-lag time-series models tested conditional effects of SHS-exposure (vs. non-exposure) on infant self-contingency for eight modality-pairings (e.g., mother gaze-infant gaze). Individual-seconds time-series models and analysis of predicted values at t₀ interrogated significant weighted-lag findings. Because prior findings link developmental risk factors with lowered self-contingency, we hypothesized that prenatal SHSSHS would predict lowered infant self-contingency.

RESULTS

Relative to non-exposed infants, those who were prenatally exposed to SHS had lower self-contingency (more variable behavior) in all eight models. Follow-up analyses showed that, given infants were likely to be in the most negative facial or vocal affect, those with prenatal SHS were more likely to make larger behavioral changes, moving into less negative or more positive affect and to alternate between gaze-on and off mother. Mothers who were exposed to SHS during pregnancy (vs. non-exposed) showed a similar, albeit less prevalent, pattern of larger changes out of negative facial affect.

CONCLUSION

These findings extend prior work linking prenatal SHS with youth dysregulated behavior, showing similar effects in infancy, a critically important period that sthe stage for future child development.

Profile of children assisted in a teaching outpatient clinic of developmental disabilities in São Paulo, Brazil

OBJECTIVE

To analyze the epidemiological and clinical profile of patients with developmental disabilities followed in a university clinic in Brazil.

METHODS

Descriptive, retrospective study, based on medical records. Children aged zero to 18 years with developmental problems, firstly evaluated between 2009 and 2018, were included. Patients with missing data or out of the age and time period established were excluded. There were nine losses and 374 patients constituted the final sample. Linear regression models were performed.

RESULTS

The mean age at the first assessment was 52.2±39.7 months and the age when the parents perceived the symptoms was 20.9±23.8 months. The most common impairment was motor associated with language delay (28.3%). The interval between the parents' perception and the first consultation was associated with the mothers' education and number of pregnancies. The age at first assessment was associated with the disability type. The number of pregnancies was associated with the child's age when the parents noticed the symptoms and at the first consultation.

CONCLUSIONS

Parents' recognition of the symptoms occurred early, however, there was a delay until the arrival at the clinic. Higher maternal education was associated with a shorter gap between perception of the developmental disability and consultation. A greater number of pregnancies was associated with a later perception of the developmental delay by the parents as well as a delay in the assessment and a wider interval between them. Motor problems were the most common in younger children, and language complaints in older ones.

The association between attention deficit hyperactivity disorder (ADHD) and smoking experience or exposure to environmental tobacco smoke among children and adolescents

INTRODUCTION

Direct and indirect smoking exposure is highly related to mental health in children. This study aimed to identify the association between exposure to smoking or secondhand smoke (SHS) and attention deficit hyperactivity disorder (ADHD).

METHODS

We used data from the Korean National Health and Nutrition Examination Survey (KNHANES) from 2007 to 2019, including variables such as diagnosed ADHD, smoking status, SHS, and urine cotinine levels among children and adolescents. We estimated the risk of ADHD according to smoking or SHS exposure in various exposure groups using adjusted logistic or linear regression models.

RESULTS

Among 16434 participants, 133 children were diagnosed with ADHD (0.8%). Of these, 58 (43.6%) were aged <12 years and 75 (56.3%) were aged ≥12 years. Smoking was significantly associated with ADHD (crude odds ratio, OR=1.48; 95% CI: 1.14-3.26 and adjusted odds ratio, AOR=1.22; 95% CI: 1.02- 1.64). SHS exposure and ADHD were attenuated after adjustment (OR=2.42; 95% CI: 1.08-4.02; AOR=1.42; 95% CI: 0.86-2.64) in the logistic regression model. Smoking history was statistically associated with a younger age of ADHD diagnosis in the linear regression model.

CONCLUSIONS

Smoking and the amount of smoking among children and adolescents was associated with ADHD.

A Potential Role for Neuroinflammation in ADHD

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioural disorder in children and adolescents. Although increases in oxidative stress and disturbances of neurotransmitter system such as the dopaminergic and abnormalities in several brain regions have been demonstrated, the pathophysiology of ADHD is not fully understood. Nevertheless, ADHD involves several factors that have been associated with an increase in neuroinflammation. This chapter presents an overview of factors that may increase neuroinflammation and play a potential role in the development and pathophysiology of ADHD. The altered immune response, polymorphisms in inflammatory-related genes, ADHD comorbidity with autoimmune and inflammatory disorders and prenatal exposure to inflammation are associated with alterations in offspring brain development and are a risk factor; genetic and environmental risk factors that may increase the risk for ADHD and medications can increase neuroinflammation. Evidence of an association between these factors has been an invaluable tool for research on inflammation in ADHD. Therefore, evidence studies have made it possible to generate alternative therapeutic interventions using natural products as anti-inflammatories that could have great potential against neuroinflammation in ADHD.

Gender differences in the association between biomarkers of environmental smoke exposure and developmental disorders in children and adolescents

Effects of environmental tobacco smoke (ETS) exposure on children and adolescent health outcomes have been attracted more and more attention. In the present study, we seek to examine the gender-specific difference association of environmental smoke exposure biomarkers and developmental disorders in children and adolescents aged 6-15 years. US nationally representative sample collected from the National Health and Nutrition Examination Survey (NHANES) 2007-2014 was enrolled (N = 4428). Developmental disorders (DDs) are defined as a positive answer to the question, "Does your child receive special education or early intervention services?" Serum cotinine and urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) were utilized as acute and chronic exposure biomarkers of ETS, respectively. Participants with serum cotinine >0.015 ng/mL were considered as with acute ETS exposure, and participants with creatinine-adjusted NNAL >0.0006 ng/mL were considered as with chronic ETS exposure. A survey logistic regression model was used to estimate the association between ETS exposure biomarkers and DDs. Additive interaction was utilized to examine the interaction of gender and biomarkers of ETS. Overall, approximately 9% of children were defined as DDs, and 65% of children had serum cotinine and urinary NNAL levels above the limit of detection. In the adjusted models, the association of ETS exposure biomarkers with DDs was only observed in girls. Girls with low cotinine levels and high urinary NNAL levels had 2.074 (95% CI: 1.012-4.247) and 1.851 (95% CI: 1.049-3.265) times higher odds of being DDs than those without ETS exposure, respectively. However, the effects of boys and NNAL exposure on DDs have additively interacted. Our findings first provided strong evidence for gender differences in the association between two tobacco metabolites and DDs in children, disclosing the public health implications and economic burdens of environmental tobacco smoke exposure.

Prenatal smoking, alcohol and caffeine exposure and offspring externalizing disorders: a systematic review and meta-analysis

BACKGROUND AND AIMS

Several studies have indicated an association between maternal prenatal substance use and offspring externalizing disorders; however, it is uncertain whether this relationship is causal. We conducted a systematic review to determine: (1) if the literature supports a causal role of maternal prenatal substance use on offspring externalizing disorders diagnosis and (2) whether these associations differ across externalizing disorders.

METHODS

We searched Web of Science, Embase, PsycINFO and Medline databases. Risk of bias assessment was conducted using the Newcastle-Ottawa Scale (NOS), and where possible meta-analysis was conducted for studies classed as low risk of bias. We included studies of any design that examined prenatal smoking, alcohol or caffeine use. Studies in non-English language, fetal alcohol syndrome and comorbid autism spectrum disorders were excluded. Participants in the included studies were mothers and their offspring. Measurements included prenatal smoking, alcohol or caffeine use as an exposure, and diagnosis of attention-deficit hyperactivity disorder (ADHD), conduct disorder (CD) and oppositional defiant disorder (ODD) in offspring as an outcome.

RESULTS

We included 63 studies, 46 of which investigated smoking and ADHD. All studies were narratively synthesized, and seven studies on smoking and ADHD were meta-analysed. The largest meta-analysis based on genetically sensitive design included 1 011 546 participants and did not find evidence for an association [odds ratio (OR)_{1-9 cigarettes}  = 0.90, 95% confidence interval (CI) = 0.83-1.11; OR _{> 10 cigarettes}  = 1.04, 95% CI = 0.79-1.36). Studies on alcohol exposure in all the outcomes reported inconsistent findings and no strong conclusions on causality can be made. Studies on caffeine exposure were mainly limited to ADHD and these studies do not support a causal effect.

CONCLUSIONS

There appears to be no clear evidence to support a causal relationship between maternal prenatal smoking and offspring attention-deficit hyperactivity disorder. Findings with alcohol and caffeine exposures and conduct disorder and oppositional-defiant disorder need more research, using more genetically sensitive designs.

Dietary and Antioxidant Vitamins Limit the DNA Damage Mediated by Oxidative Stress in the Mother-Newborn Binomial

During pregnancy, appropriate nutritional support is necessary for the development of the foetus. Maternal nutrition might protect the foetus from toxic agents such as free radicals due to its antioxidant content. In this study, 90 mothers and their children were recruited. DNA damage mediated by oxidative stress (OS) was determined by the levels of 8-hidroxy-2′-deoxyguanosine (8-OHdG) in the plasma of women and umbilical cord blood. The mothers and newborns were categorised into tertiles according to their 8-OHdG levels for further comparison. No relevant clinical differences were observed in each group. A strong correlation was observed in the mother−newborn binomial for 8-OHdG levels (Rho = 0.694, p < 0.001). In the binomial, a lower level of 8-OHdG was associated with higher consumption of calories, carbohydrates, lipids, and vitamin A (p < 0.05). In addition, the levels of 8-OHdG were only significantly lower in newborns from mothers with a higher consumption of vitamin A and E (p < 0.01). These findings were confirmed by a significant negative correlation between the 8-OHdG levels of newborns and the maternal consumption of vitamins A and E, but not C (Rho = −0.445 (p < 0.001), −0.281 (p = 0.007), and −0.120 (p = 0.257), respectively). Multiple regression analysis showed that the 8-OHdG levels in mothers and newborns inversely correlated with vitamin A (β = −1.26 (p = 0.016) and −2.17 (p < 0.001), respectively) and pregestational body mass index (β = −1.04 (p = 0.007) and −0.977 (p = 0.008), respectively). In conclusion, maternal consumption of vitamins A and E, but not C, might protect newborns from DNA damage mediated by OS.

Informing women about the risks of exposing babies to tobacco smoke: outreach and education efforts using Facebook "boost posts"

Maternal smoking is associated with a host of negative health outcomes, including an increased risk of children developing attention-deficit/hyperactivity disorder (ADHD). This study evaluated the efficacy of health messages disseminated through Facebook Ads focused on reducing tobacco smoke exposure during pregnancy. Two message versions were promoted via post advertisements on Facebook-a static infographic and a video containing an animated version of the infographic. The reach of and engagement with each message version was evaluated. Comments made to the posts were assessed using content analysis. The infographic reached approximately 60,000 people and the video reached about 16,000 people. The average costs were $10.00 and $40.00 per 1,000 people reached for the infographic- and video-based posts, respectively. While there was no engagement with the video, the infographic was liked (n = 157), given alternative likes (n = 59), shared (n = 171 to 341), and commented on (n = 221). About one-quarter of comments contained a personal narrative and mentions of health history related to ADHD and/or smoking. Comments were more often negative (than positive) (16.6% vs 3.9%) and expressed skepticism more often than message acceptance (21.5% vs 12.2%). Facebook users were more responsive to the infographic (compared to the video) and static posts were a preferred channel (i.e., higher engagement at a lower cost) to disseminate messages when using the boost post feature on Facebook for health education. Our review of the comments provided insights into message acceptance and guidance for future social media-based health message campaigns. However, it is not known whether and if so, how, these findings on message exposure would correlate with behavioral intentions or changes in behavior, such as intentions to quit smoking or smoking cessation.

The Association between ADHD and Environmental Chemicals-A Scoping Review

The role of environmental chemicals in the etiology of attention deficit hyperactivity disorder (ADHD) has been of interest in recent research. This scoping review aims to summarize known or possible associations between ADHD and environmental exposures to substances selected as priority chemicals of the European Human Biomonitoring Initiative (HBM4EU). Literature searches were performed in PubMed to identify relevant publications. Only meta-analyses and review articles were included, as they provide more extensive evidence compared to individual studies. The collected evidence indicated that lead (Pb), phthalates and bisphenol A (BPA) are moderately to highly associated with ADHD. Limited evidence exists for an association between ADHD and polycyclic aromatic hydrocarbons (PAHs), flame retardants, mercury (Hg), and pesticides. The evidence of association between ADHD and cadmium (Cd) and per- and polyfluoroalkyl substances (PFASs) based on the identified reviews was low but justified further research. The methods of the individual studies included in the reviews and meta-analyses covered in the current paper varied considerably. Making precise conclusions in terms of the strength of evidence on association between certain chemicals and ADHD was not straightforward. More research is needed for stronger evidence of associations or the lack of an association between specific chemical exposures and ADHD.

Maternal tobacco smoking and offspring autism spectrum disorder or traits in ECHO cohorts

Given inconsistent evidence on preconception or prenatal tobacco use and offspring autism spectrum disorder (ASD), this study assessed associations of maternal smoking with ASD and ASD-related traits. Among 72 cohorts in the Environmental Influences on Child Health Outcomes consortium, 11 had ASD diagnosis and prenatal tobaccosmoking (n = 8648). and 7 had Social Responsiveness Scale (SRS) scores of ASD traits (n = 2399). Cohorts had diagnoses alone (6), traits alone (2), or both (5). Diagnoses drew from parent/caregiver report, review of records, or standardized instruments. Regression models estimated smoking-related odds ratios (ORs) for diagnoses and standardized mean differences for SRS scores. Cohort-specific ORs were meta-analyzed. Overall, maternal smoking was unassociated with child ASD (adjusted OR, 1.08; 95% confidence interval [CI], 0.72-1.61). However, heterogeneity across studies was strong: preterm cohorts showed reduced ASD risk for exposed children. After excluding preterm cohorts (biased by restrictions on causal intermediate and exposure opportunity) and small cohorts (very few ASD cases in either smoking category), the adjusted OR for ASD from maternal smoking was 1.44 (95% CI, 1.02-2.03). Children of smoking (versus non-smoking) mothers had more ASD traits (SRS T-score + 2.37 points, 95% CI, 0.73-4.01 points), with results homogeneous across cohorts. Maternal preconception/prenatal smoking was consistently associated with quantitative ASD traits and modestly associated with ASD diagnosis among sufficiently powered United States cohorts of non-preterm children. Limitations resulting from self-reported smoking and unmeasured confounders preclude definitive conclusions. Nevertheless, counseling on potential and known risks to the child from maternal smoking is warranted for pregnant women and pregnancy planners. LAY SUMMARY: Evidence on the association between maternal prenatal smoking and the child's risk for autism spectrum disorder has been conflicting, with some studies reporting harmful effects, and others finding reduced risks. Our analysis of children in the ECHO consortium found that maternal prenatal tobacco smoking is consistently associated with an increase in autism-related symptoms in the general population and modestly associated with elevated risk for a diagnosis of autism spectrum disorder when looking at a combined analysis from multiple studies that each included both pre- and full-term births. However, this study is not proof of a causal connection. Future studies to clarify the role of smoking in autism-like behaviors or autism diagnoses should collect more reliable data on smoking and measure other exposures or lifestyle factors that might have confounded our results.

Prenatal nicotine alters development of the laterodorsal tegmentum: Possible role for attention-deficit/hyperactivity disorder and drug dependence

As we cycle between the states of wakefulness and sleep, a bilateral cholinergic nucleus in the pontine brain stem, the laterodorsal tegmentum (LDT), plays a critical role in controlling salience processing, attention, behavioral arousal, and electrophysiological signatures of the sub- and microstates of sleep. Disorders involving abnormal alterations in behavioral and motivated states, such as drug dependence, likely involve dysfunctions in LDT signaling. In addition, as the LDT exhibits connectivity with the thalamus and mesocortical circuits, as well as receives direct, excitatory input from the prefrontal cortex, a role for the LDT in cognitive symptoms characterizing attention-deficit/hyperactivity disorder (ADHD) including impulsivity, inflexibility, and dysfunctions of attention is suggested. Prenatal nicotine exposure (PNE) is associated with a higher risk for later life development of drug dependence and ADHD, suggesting alteration in development of brain regions involved in these behaviors. PNE has been shown to alter glutamate and cholinergic signaling within the LDT. As glutamate and acetylcholine are major excitatory mediators, these alterations would likely alter excitatory output to target regions in limbic motivational circuits and to thalamic and cortical networks mediating executive control. Further, PNE alters neuronal development and transmission within prefrontal cortex and limbic areas that send input to the LDT, which would compound effects of differential processing within the PNE LDT. When taken together, alterations in signaling in the LDT are likely to play a role in negative behavioral outcomes seen in PNE individuals, including a heightened risk of drug dependence and ADHD behaviors.

Identification and Characterization of Influential Factors in Susceptibility to Attention Deficit Hyperactivity Disorder Among Preschool-Aged Children

Attention deficit hyperactivity disorder (ADHD) is the most common childhood-onset neurodevelopmental disorder. Currently, increasing amounts of attention have been focused on the epidemiologic profiling of ADHD in children, viewed as a continuously distributed risk dimension throughout the whole lifespan. This study aimed to identify and characterize potential influential factors susceptible to ADHD-related symptoms among preschool-aged children. A comprehensive questionnaire was self-designed for both children and their parents or guardians and was distributed to 30 kindergartens from Beijing and Hebei, collecting potential influential factors in susceptibility to ADHD. ADHD was assessed by the Conner’s Abbreviated Symptom Questionnaire (C-ASQ), and 7,938 children were analyzed. Least absolute shrinkage and selection operator (LASSO) regression and hierarchical degree of adjustment were used to control possible covariates. Five factors, namely, children’s secondhand smoking exposure, breastfeeding duration, sleep mode, maternal pregnancy smoking exposure, and parental self-rating for patience, were identified to be independently and significantly associated with ADHD susceptibility. Meanwhile, dose–response relationships were observed between breastfeeding duration, parental self-rating for patience, and ADHD-related symptoms. Finally, a nomogram model was created for predicting ADHD susceptibility based on significant and conventional attributes under each criterion.

Familial confounding affected the associations between maternal smoking during pregnancy and offspring speech and language, scholastic and coordination disorders

AIM

This study examined the associations between prenatal smoking and speech and language, scholastic, coordination and mixed developmental disorders in offspring, using sibling and population controls.

METHODS

National Finnish registers were used to identify all 690 654 singletons born between 1996 and 2007 and any cases diagnosed with speech and language, scholastic, coordination and mixed developmental disorders by the end of 2012. Cases were compared to population controls, biological full-siblings and maternal half-siblings born during the same period. Conditional logistic regression was used to assess any associations between smoking during pregnancy and the selected developmental disorders.

RESULTS

Prenatal smoking was higher in the mothers of the 27 297 cases (21.7%) than the 99 876 population controls (14.5%). The adjusted odds ratio for smoking throughout pregnancy, and any diagnosis of speech and language, scholastic, coordination or mixed developmental disorders, was 1.29 (95% confidence interval 1.24-1.34). However, when we compared a subsample of 15 406 cases and their 20 657 siblings, the association was no longer statistically significant (odds ratio 1.09, 95% confidence interval 0.98-1.21).

CONCLUSION

The sibling comparisons suggested that the associations between prenatal smoking and speech and language, scholastic, coordination and mixed developmental disorders were confounded by familial factors shared by differentially exposed siblings.

Time of onset and/or diagnosis of ADHD in European children: a systematic review

BACKGROUND

Attention-Deficit/ Hyperactivity Disorder (ADHD) is one of the most common childhood neurobehavioral conditions. Symptoms related to this disorder cause a significant impairment in school tasks and in the activities of children's daily lives; an early diagnosis and appropriate treatment could almost certainly help improve their outcomes. The current study, part of the Models Of Child Health Appraised (MOCHA) project, aims to explore the age at which children experience the onset or diagnosis of ADHD in European countries.

METHODS

A systematic review was done examining the studies reporting the age of onset/diagnosis (AO/AD) of ADHD in European countries (28 European Member States plus 2 European Economic Area countries), published between January 1, 2010 and December 31, 2019. Of the 2276 identified studies, 44 met all the predefined criteria and were included in the review.

RESULTS

The lowest mean AO in the children diagnosed with ADHD alone was 2.25 years and the highest was 7.5 years. It was 15.3 years in the children with ADHD and disruptive behaviour disorder. The mean AD ranges between 6.2 and 18.1 years.

CONCLUSIONS

Our findings indicate that there is a wide variability in both the AO and AD of ADHD, and a too large distance between AO and AD. Since studies in the literature suggest that an early identification of ADHD symptoms may facilitate early referral and treatment, it would be important to understand the underlying reasons behind the wide variability found.

TRIAL REGISTRATION

PROSPERO registration: CRD42017070631 .

Prenatal environmental tobacco smoke exposure alters children's cognitive control circuitry: A preliminary study

BACKGROUND AND OBJECTIVES

Prenatal exposure to environmental tobacco smoke (ETS) is associated with increased attention problems in children, however, the effects of such exposure on children's brain structure and function have not been studied. Herein, we probed effects of prenatal ETS on children's cognitive control circuitry and behavior.

METHODS

Forty-one children (7-9 years) recruited from a prospective longitudinal birth cohort of non-smoking mothers completed structural and task-functional magnetic resonance imaging to evaluate effects of maternal ETS exposure, measured by maternal prenatal urinary cotinine. Attention problems and externalizing behaviors were measured by parent report on the Child Behavior Checklist.

RESULTS

Compared to non-exposed children, exposed children had smaller left and right thalamic and inferior frontal gyrus (IFG) volumes, with large effect sizes (p-FDR < .05, Cohen's D range from 0.79 to 1.07), and increased activation in IFG during the resolution of cognitive conflict measured with the Simon Spatial Incompatibility Task (38 voxels; peak t(25) = 5.25, p-FWE = .005). Reduced thalamic volume was associated with increased IFG activation and attention problems, reflecting poor cognitive control. Mediation analyses showed a trend toward left thalamic volume mediating the association between exposure and attention problems (p = .05).

CONCLUSIONS

Our findings suggest that maternal ETS exposure during pregnancy has deleterious effects on the structure and function of cognitive control circuitry which in turn affects attentional capacity in school-age children. These findings are consistent with prior findings documenting the effects of active maternal smoking on chidlren's neurodevleoment, pointing to the neurotixicity of nicotine regardless of exposure pathway.

A biomarker-based study of prenatal smoking exposure and autism in a Finnish national birth cohort

Maternal exposure to tobacco smoke during pregnancy is a common and persistent exposure linked to adverse neurodevelopmental outcomes in the offspring. However, previous studies provide mixed evidence regarding the relationship between prenatal smoking and offspring autism. This study used cotinine level, a biomarker for nicotine, to investigate the relationship between prenatal smoking and autism. The authors conducted a population-based case-control study nested in a national cohort of all births in Finland from 1987 to 2005. Cases diagnosed with childhood autism (ICD-10/9 code F84.0/299.0) through 2007 were identified using data from linked national registers. Each case was matched with a control on date of birth (±30 days), sex, and place of birth (N = 962 pairs). Maternal serum cotinine levels were prospectively measured in first- to early second-trimester serum samples archived in a national biobank using a quantitative immunoassay. Data were analyzed using conditional logistic regression. Prenatal maternal levels of serum cotinine were not associated with the odds of autism, whether cotinine was classified continuously, by deciles, or using previously defined categories corresponding to probable maternal smoking status. After adjusting for maternal age, paternal age, previous births, and any history of parental psychiatric disorder, the odds ratio for categorical high versus low cotinine, using a 3-level exposure variable, was 0.98 (95% CI = 0.76, 1.26; p = 0.88). In conclusion, this national birth cohort-based study does not provide evidence for an association between maternal cotinine, a biomarker of maternal smoking, and risk of autism. LAY SUMMARY: This study explored whether prenatal exposure to tobacco smoke in mothers is related to the diagnosis of autism in their children, by measuring the levels of cotinine, a biomarker for tobacco exposure, in stored serum samples drawn from mothers during pregnancy. The levels of cotinine in the mothers of children diagnosed with autism were similar to those in the mothers of control children of similar age and gender distribution.

Association of Prenatal, Early Postnatal, or Current Exposure to Secondhand Smoke With Attention-Deficit/Hyperactivity Disorder Symptoms in Children

IMPORTANCE

Few studies have investigated the association between the exposure window (prenatal, early postnatal, and current period) of secondhand smoke (SHS) and attention-deficit/hyperactivity disorder (ADHD) symptoms and subtypes in children.

OBJECTIVE

To evaluate the associations of prenatal, early postnatal, or current SHS exposure with ADHD symptoms and subtypes among school-aged children.

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study, 48 612 children aged 6 to 18 years from elementary and middle schools in Liaoning province, China, between April 2012 and January 2013 were eligible for participation. Data on SHS exposure and ADHD symptoms and subtypes for each child were collected via questionnaires administered to parents or guardians by school teachers. Data were analyzed from September 14 to December 2, 2020.

MAIN OUTCOMES AND MEASURES

The ADHD symptoms and subtypes (inattention, hyperactivity-impulsivity, and combined) were measured based on a validated tool developed from the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition). Generalized linear mixed models were evaluated to estimate the association of SHS exposure with ADHD symptoms and subtypes.

RESULTS

A total of 45 562 participants completed the questionnaires and were included in this study (22 905 girls [50.3%]; mean [SD] age, 11.0 [2.6] years; 2170 [4.8%] with ADHD symptoms). Compared with their unexposed counterparts, children who were ever exposed (odds ratio [OR], 1.50; 95% CI, 1.36-1.66) or always exposed to SHS (OR, 2.88; 95% CI, 2.55-3.25) from pregnancy to childhood had higher odds of having ADHD symptoms and subtypes (ORs ranged from 1.46 [95% CI, 1.31-1.62] to 2.94 [95% CI, 2.09-4.13]). Compared with their unexposed counterparts, children with SHS exposure had higher odds of having ADHD symptoms when exposed in the prenatal period (OR, 2.28; 95% CI, 2.07-2.51), early postnatal period (OR, 1.47; 95% CI, 1.29-1.68), or current period (OR, 1.20; 95% CI, 1.09-1.31). Compared with their unexposed counterparts, children whose fathers smoked 10 or more cigarettes/d on both weekdays and weekends had higher odds of having ADHD symptoms and subtypes (ORs ranged from 1.48 [95% CI, 1.28-1.70] to 2.25 [95% CI, 1.29-3.93]).

CONCLUSIONS AND RELEVANCE

Being exposed to SHS from pregnancy to childhood was associated with higher odds of having ADHD symptoms and subtypes among school-aged children, and the associations were somewhat stronger for SHS exposure during prenatal and early postnatal periods. Our findings highlight the important public health implications of reducing SHS exposure, which may decrease the health and economic burdens of individuals with ADHD.

Suicidal ideation and attempt in adolescents exposed to maternal smoking across pregnancy and childhood: A 20-year prospective cohort study

BACKGROUND

Few studies investigated the association between maternal smoking during pregnancy and offspring suicide risk, none considering postnatal smoking exposure. We investigated associations between maternal smoking patterns during the pre- and postnatal periods and adolescent suicidal ideation and attempt.

METHODS

We identified longitudinal patterns of maternal smoking from the prenatal period to the end of childhood (children's age 12 years, 10 assessments) among participants in the Québec Longitudinal Study of Child Development (N = 1623). We estimated associations between maternal smoking patterns and offspring self-reported suicidal ideation and attempt (ages 13-20). Background confounding factors (e.g., socioeconomic, familial, mental health) were controlled using propensity score inverse-probability weighting (IPW).

RESULTS

Participants reporting suicidal ideation and attempt were 9.3% and 8.4%, respectively. We identified four maternal smoking patterns: non-smoking (66.5%), increasing (5.5%), decreasing (9.3%), persistent (18.5%). Children exposed to persistent (OR=2.92, CI=1.99-4.30) and increasing (OR=2.06, CI=1.13-3.74) maternal smoking were more likely to attempt suicide, compared to non-exposed children. Accounting for confounding factors using IPW fully explained the association between increasing smoking and suicide attempt (OR=0.95, CI=0.39-2.09) but only reduced the association between persistent exposure and suicide attempt (OR=2.30, CI=1.04-4.99). No increased suicide attempt risk was found for children of mothers with a decreased smoking pattern. We found no associations for suicidal ideation.

LIMITATIONS

Propensity score cannot account for unmeasured confounding factors; attrition limits generalizability.

CONCLUSIONS

Offspring of mothers who smoked persistently and heavily prenatally and postnatally were at increased risk of suicide attempt in adolescence. Future studies should elucidate biological and psychosocial mechanisms potentially at play in these associations.

Prenatal and perinatal factors associated with ADHD risk in schoolchildren: EPINED epidemiological study

The aim of this study is to assess the relationship between pre- and perinatal factors and ADHD in a sample of scholars exploring differences between ADHD presentations and spectrum of severity. A total of 6720 scholars (aged 3-4 and 10-11) participated in a double-phase epidemiologic cross-sectional study (Epidemiological Study of Neurodevelopmental Disorders, EPINED), and a sample of 646 scholars (ADHD risk, ASD risk and controls without risk) were individually assessed in the second phase of the study. The ADHD diagnosis, based on DSM-5 criteria, was performed with the Kiddie-Schedule for Affective Disorders & Schizophrenia, Present & Lifetime Version. Associations for the different ADHD presentations between prenatal, perinatal and postnatal factors and ADHD (n = 168), subclinical ADHD (n = 88) and non-ADHD (n = 310) were analysed. Logistic regression models showed that gestational diabetes (p = 0.012), instrumental delivery (p = 0.011), family history of psychopathology (p = 0.033) and maternal ADHD phenotype (p = 0.023) were associated with ADHD. These factors were related to the hyperactive-impulsive and combined presentations, but they were not related to the inattentive presentation. Maternal weight gain was associated with subclinical ADHD. In conclusion, metabolic disorder in the pregnancy, difficulties in childbirth and specific family phenotype were related to ADHD, specifically with hyperactive-impulsive presentation, but not in subclinical ADHD.

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.

Maternal Vitamin D Levels and the Risk of Offspring Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Recent evidence has highlighted the importance of vitamin D in the development of the central nervous system. Some studies have shown an association between maternal vitamin D deficiency during pregnancy and offspring attention-deficit/hyperactivity disorder (ADHD) symptoms based on parent or teacher ratings. There are no previous studies on early pregnancy 25-hydroxyvitamin D [25(OH)D] levels and the risk of diagnosed offspring ADHD. Our aim was to examine maternal 25(OH)D levels in early pregnancy and offspring ADHD.

METHOD

In this nationwide population-based case-control study, 1,067 ADHD cases (born between 1998 and 1999 and diagnosed according to the International Classification of Diseases) and 1,067 matched controls were identified from Finnish registers. Maternal 25(OH)D levels were measured using quantitative immunoassay from maternal sera, collected during the first trimester and archived in the national biobank. Conditional logistic regression was used to examine the association between maternal 25(OH)D and offspring ADHD.

RESULTS

There was a significant association between decreasing log-transformed maternal 25(OH)D levels and offspring ADHD both in the unadjusted analyses (odds ratio 1.65; 95% CI 1.33-2.05; p < .001) and in the analyses adjusting for maternal socioeconomic status and age (odds ratio 1.45; 95% CI 1.15-1.81; p = .002). Analyses by quintiles of maternal 25(OH)D levels in the lowest versus highest quintile revealed an adjusted odds ratio for offspring ADHD of 1.53 (95% CI 1.11-2.12; p = .010).

CONCLUSION

This study demonstrated an association between low maternal 25(OH)D during pregnancy and an elevated risk for offspring ADHD. If replicated in independent samples, this finding may have significant public health implications.

Maternal serum Vitamin B12 and offspring attention-deficit/hyperactivity disorder (ADHD)

Maternal Vitamin B12 deficiency during pregnancy is associated with offspring neuropsychiatric disorders. Few previous studies examining this association with attention-deficit/hyperactivity disorder (ADHD) report inconsistent findings. The study examines the association between maternal serum Vitamin B12 levels and offsprings' risk of ADHD. This study is based on the Finnish Prenatal Study of ADHD with a nested case-control design. All the singleton children born in Finland between January 1998 and December 1999 and diagnosed with ADHD were included in the study. A total of 1026 cases were matched with an equal number of controls on sex, date of birth and place of birth. Maternal Vitamin B12 levels were assessed using a chemiluminescence microparticle immunoassay and archived from maternal serum banks, collected during the first and early second trimester of pregnancy. Lower maternal Vitamin B12 levels when analyzed as a continuous variable was not associated with offspring ADHD (aOR 0.97, 95% CI 0.79-1.18, p = 0.75). No significant associations were seen in the lowest quintile of Vitamin B12 levels (aOR 0.96, 95% CI 0.73-1.27, p = 0.80). This is the first study examining maternal sera Vitamin B12 levels during early pregnancy and offspring ADHD. The result suggests that Vitamin B12 deficiency during early pregnancy has specificity for some disorders but not with offspring ADHD.

Association between postnatal second-hand smoke exposure and ADHD in children: a systematic review and meta-analysis

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder which is caused by the interplay of genetic and environmental risk factors such as second-hand smoke (SHS). The association between postnatal exposure to SHS and ADHD risk in children was still inconclusive. We performed a systematic review and meta-analysis to explore the definite association. We searched for relevant studies from PubMed, Embase, Ovid, and Web of Science databases up to January 2020. We used random effect models to calculate pooled odds ratio (OR) with 95% confidence interval (CI). Subgroup analyses and sensitive analyses were also performed to solve the heterogeneity. According to our inclusion criteria, 9 studies including 6 cross-sectional studies, 2 cohort studies, and 1 case-control study were included in the final analysis. Postnatal exposure to SHS increased the risk of ADHD in children (OR: 1.60; 95% CI: 1.37-1.87). Children who exposed to SHS were found a slight risk for conduct problems (OR: 1.33, 95% CI: 1.00-1.77). Among the studies which used cotinine as a biomarker for SHS exposure, a lower pooled OR (OR = 1.16, 95%CI = 1.01, 1.33) was observed between cotinine and ADHD in children. Our meta-analysis results suggested that SHS exposure may be a risk factor for ADHD. We also found that SHS exposure may be associated with some adverse behavioral outcomes. More prospective studies should be conducted to confirm the relationship between SHS exposure and ADHD in children.

Health Disparities in Tobacco Use and Exposure: A Structural Competency Approach

Fourteen percent of US adults use tobacco products. Because many of those who use tobacco are parents and/or caregivers, children are disproportionately exposed to tobacco smoke. People who use tobacco products often become addicted to nicotine, resulting in tobacco dependence, a chronic, relapsing disease. Tobacco use and exposure are more likely to occur in vulnerable and marginalized groups, including those living in poverty. Although some view tobacco use as a personal choice, evidence suggests that structural forces play an important role in tobacco uptake, subsequent nicotine addiction, and perpetuation of use. Viewing tobacco use and tobacco dependence through a structural competency lens promotes recognition of the larger systemic forces perpetuating tobacco use, including deliberate targeting of groups by the tobacco industry, lack of enforcement of age-for-sale laws, inferior access to health insurance and health care, poor access to cessation resources, and economic stress. Each of these forces perpetuates tobacco initiation and use; in turn, tobacco use perpetuates the user's adverse health and economic conditions. Pediatricians are urged to view family tobacco use as a social determinant of health. In addition to screening adolescents for tobacco use and providing resources and treatment of tobacco dependence, pediatricians are encouraged to systematically screen children for secondhand smoke exposure and support family members who smoke with tobacco cessation. Additionally, pediatricians can address the structural issues perpetuating tobacco use by becoming involved in policy and advocacy initiatives.

Prenatal and perinatal risk factors for anxiety disorders among children and adolescents: A systematic review

BACKGROUND

Prenatal and perinatal risk factors for anxiety disorders have rarely been studied, even though they are highly prevalent in children and adolescents. It is important to identify the common risk factors, so that targeted preventive care and early interventions can be provided.

METHODS

A systematic review of the PubMed and PsycInfo databases was conducted to 25 October 2019, according to the Preferred Reporting Items of Systematic Reviews and Meta-analyses guidelines. The protocol was registered on the Prospective Register of Systematic Reviews and the quality assessment was carried out using the Joanna Briggs tools.

RESULTS

The review identified 31 studies from eight countries, including three register studies. Cohort sizes ranged from 69 to 89,404 and diagnoses cases ranged from 4 to 7867. Although various risk factors had been researched, only few of them had been repeatedly studied and the findings were highly inconsistent. The associations between the different risk factors and anxiety disorders seemed weak compared to many other psychiatric disorders, but preterm birth and maternal somatic illnesses may increase the risk for anxiety disorders in offspring.

LIMITATIONS

The studies varied considerably by study design, risk factors and anxiety disorders studied, sample sizes and follow up periods.

CONCLUSIONS

Prenatal and perinatal risk factors for anxiety disorders have been under-researched, compared to other psychiatric disorders. Our systematic review found weak links to prenatal events, but flagged up preterm birth and maternal somatic illnesses as possible avenues for future research.

The effects of prenatal cigarette and e-cigarette exposure on infant neurobehaviour: A comparison to a control group

BACKGROUND

Infant neurobehaviour provides an insight into the development of the central nervous system during infancy, with behavioural abnormalities highlighting a cause for concern. Research has demonstrated that prenatal exposure to cigarettes leads to deficits within neurobehavioural development, along with negative birth outcomes detrimental to subsequent development. With the growing use of e-cigarettes amongst pregnant women, this study explores how prenatal e-cigarette exposure compares to prenatal cigarette exposure.

METHODS

Eighty-three infants were involved in the study, either exposed prenatally to cigarettes or e-cigarettes or not exposed to either. Differences were assessed between these three groups for birth outcomes and scores on the Neonatal Behavioural Assessment Scale (NBAS) at one month of age.

FINDINGS

Both cigarette and e-cigarette exposed infants had a significantly greater number of abnormal reflexes (p = ·001; p  =  ·002). For both self-regulation and motor maturity, cigarette exposed infants performed significantly worse (p = ·010; p = ·002), with e-cigarette exposed infants having decreased motor maturity (p = ·036) abilities and marginally decreased for self-regulation (p = ·057). Birth outcomes, namely birthweight, gestation and head circumference, did not differ for e-cigarette exposed infants compared with infants who were not prenatally exposed to nicotine. Cigarette exposed infants had a significantly lower birthweight (p = ·021) and reduced head circumference (p = ·008) in comparison to non-exposed infants.

INTERPRETATION

To our knowledge, this is the first research study assessing a neurological outcome as a result of e-cigarette exposure. Findings of this have potentially important implications for public health policies regarding the safety and use of e-cigarettes throughout pregnancy.

FUNDING

This research was funded by a doctoral training partnership scholarship via the ESRC, ES/P000762/1.

Gender Differences in the Outcome of Offspring Prenatally Exposed to Drugs of Abuse

Despite great efforts to warn pregnant women that drugs of abuse impact development of the embryo and the fetus, the use of legal and illegal drugs by childbearing women is still a major public health concern. In parallel with well-established teratogenic effects elicited by some drugs of abuse, epidemiological studies show that certain psychoactive substances do not induce birth defects but lead to subtle neurobehavioral alterations in the offspring that manifest as early as during infancy. Although gender differences in offspring susceptibility have not been fully investigated, a number of longitudinal studies indicate that male and female progeny exposed in utero to drugs of abuse show different vulnerabilities to deleterious effects of these substances in cognitive, executive, and behavioral domains. Here, we briefly review the existing literature focusing on gender differences in the neurobehavioral consequences of maternal exposure to drugs of abuse. Overall, the data strongly indicate that male exposed progeny are more susceptible than female to dysfunctions in cognitive processing and emotional regulation. However, insights into the mechanisms determining this natural phenomenon are not currently available. Our analysis prompts future investigations to implement clinical studies including the influence of gender/sex as a biological variable in the outcome of offspring prenatally exposed to drugs of abuse.

The role of teratogens in neural crest development

The neural crest (NC), discovered by Wilhelm His 150 years ago, gives rise to a multipotent migratory embryonic cell population that generates a remarkably diverse and important array of cell types during the development of the vertebrate embryo. These cells originate in the neural plate border (NPB), which is the ectoderm between the neural plate and the epidermis. They give rise to the neurons and glia of the peripheral nervous system, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies are a class of congenital diseases resulting from the abnormal induction, specification, migration, differentiation or death of NC cells (NCCs) during embryonic development and have an important medical and societal impact. In general, congenital defects affect an appreciable percentage of newborns worldwide. Some of these defects are caused by teratogens, which are agents that negatively impact the formation of tissues and organs during development. In this review, we will discuss the teratogens linked to the development of many birth defects, with a strong focus on those that specifically affect the development of the NC, thereby producing neurocristopathies. Although increasing attention is being paid to the effect of teratogens on embryonic development in general, there is a strong need to critically evaluate the specific role of these agents in NC development. Therefore, increased understanding of the role of these factors in NC development will contribute to the planning of strategies aimed at the prevention and treatment of human neurocristopathies, whose etiology was previously not considered.