Autistic traits are continuously distributed in the general population. The associations between autistic traits and intellectual functioning and/or behavioural difficulties, and the impact of intellectual functioning on behavioural difficulties are unclear. The study aims to describe the distribution of autistic traits in a population-based cross-sectional sample of children. Further aims are to examine the association between intellectual functioning and autistic traits, and between autistic traits and behavioural difficulties. Wechsler scales and ratings of autistic traits and behavioural problems in 874 children aged 7-9 years in the Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy (SELMA) study were assessed. We found a continuous distribution of autistic traits. Intellectual functioning was negatively associated with autistic traits but not with behavioural difficulties. Behavioural difficulties were associated with autistic traits.

Low motor competence (MC) has been associated with lower physical activity (PA) and long-term health risks in children. Less is known about sex-specific patterns and associations during early school age. The aim of this study was to explore how motor difficulties are associated with PA levels, screen time, and organised sports participation (OSP). Data from 479 children, seven years of age, participating in the Swedish Environmental, Longitudinal, Mother and child, Asthma, and allergy (SELMA) pregnancy cohort study were used. MC and activity-related outcomes were assessed with questionnaires answered by parents. Associations between MC and outcomes were evaluated using logistic regression models adjusted for sex, overweight, and parental education level. Sex differences were investigated with interaction analyses and in stratified models. Children with motor difficulties had the same level of PA as their peers, but more screen time and lower OSP. Compared with children with normal MC, boys with motor difficulties had lower rates of OSP, but girls did not. This indicates that the identification and compensatory support for motor difficulties for boys at an early age, as well as the development of inclusive leisure time activities, are of importance to facilitate health-promoting activities on equal terms.

Intelligence tests predict academic achievement in typically developed children, however if this is the case also in children with attention-deficit/hyperactivity disorder (ADHD) and/or autism spectrum disorder (ASD) is not clear. This systematic review and meta-analysis examined if Wechsler intelligence scales predict academic achievement and/or grades in children, ages 6-16 years, with ADHD and/or ASD. We searched the databases PubMed, PsycINFO and Education Research Complete for studies published between 2000 and 2023. We used the Newcastle-Ottawa Scale to assess risk of bias. Narrative synthesis and meta-analysis were performed. Twelve studies (ADHD n = 1,834, ASD n = 176) were included in the review, and six samples (ADHD n = 1,112) of those were included in the meta-analyses. The results of the meta-analyses showed moderate overall weighted correlations between IQ and word reading, written language, and mathematics respectively. Similarly, the overall weighted correlations between processing speed and the aforementioned domains of academic achievement were moderate. Meta-analysis with additional Wechsler scales composite scores could not be conducted. In the narrative synthesis, Full Scale IQ was associated with academic achievement in both ADHD and ASD, and grades in ADHD. The limited number of ASD participants and the heterogeneity of the samples need to be considered when interpreting results. Generally, the results indicate that Wechsler scales are valuable in predicting academic achievement in children with ADHD or ASD. Motivation and other factors related with academic achievement need to be further explored in these groups. 

Background Childhood gender nonconformity is related to psychological distress and behavioral difficulties. Similarly, there is evidence for a link between gender nonconformity, or gender dysphoria in some studies, and autism spectrum disorder and related traits. Our knowledge on those associations mostly originates from clinical populations, which might lead to overestimation. Thus, this study aimed to assess associations between gender nonconformity and behavioral difficulties in a population-based study.Methods In the Swedish Environmental Longitudinal, Mother and Child, Asthma and Allergy (SELMA) study, cross-sectional associations between gender-specific play behavior and behavioral outcomes and autistic traits were investigated among 718 children at 7-years of age. Play behavior was measured using the Preschool Activities Inventory; behavioral outcomes and autistic traits were measured with the Strengths and Difficulties Questionnaire and the Social Responsiveness Scale, respectively. Linear and logistic regression analyses were performed.Results Higher composite play behavior scores (indicating either increased masculine or decreased feminine play behavior) were associated with increased autistic trait scores in girls (beta = 0.13; 95% confidence interval [CI] = 0.00, 0.26). Furthermore, higher composite scores were shown to be associated with behavioral difficulties in both girls (beta = 0.11; 95% CI = 0.04, 0.18) and boys (beta = 0.10; 95% CI = 0.02, 0.19). Additionally, higher feminine scores were related with increased problems in peer relationships in boys (beta = 0.04; 95% CI = 0.00, 0.07).Conclusions This study suggests a link between gender nonconforming play behavior and autistic traits as well as behavioral difficulties among children in a non-clinical population, which calls attention to the necessity of supporting children with gender nonconformity from early ages.

The Working Memory Index (WMI) in the Wechsler Intelligence Scale for Children (WISC) has been suggested to be associated with ADHD symptoms. The relationship between WMI and ADHD symptoms in the general population is not clear. The study aimed to examine the association between working memory (WM) and behavioral regulation (BR), and hyperactivity/inattention (HI) in a general population sample of 7-8-year-olds, and whether general intellectual functioning is associated with BR and HI. The study also examined if those with low WMI also fulfill elevated ADHD criteria. The study group (N = 865) was assessed with the WISC (Fourth edition), the Behavior Rating Inventory of Executive Function, the Strengths and Difficulties Questionnaire, and the Five to Fifteen Questionnaire, and divided into three groups based on WM function, and in relation to BR and/or HI problems. The associations between WM and BR, and WM and HI, including intellectual functioning as covariate, were examined. WM deficits were found in 22%, but the majority of those had no BR or HI problems. Four percent in the study group had WM deficits combined with BR and/or HI problems, and in about one third of those inattentive ADHD criteria were fulfilled. WM and prosocial behavior were associated with BR and HI. WM deficits measured with WISC WMI in 7-8-year-olds do not always signal BR and/or HI problems.

This study comprehensively examines maternal and perinatal conditions associated with autism spectrum disorder (ASD) in a total population sample with individually confirmed diagnoses from South Sweden. Following thorough review of medical records, 996 cases were ascertained and classified based on level of intellectual disability, ASD severity and family-history of ASD. 10 controls per case were randomly selected from the population (N=9,960). Multiple maternal and perinatal conditions were associated with increased risk for ASD, but associations varied by ASD comorbid conditions. Only high maternal BMI was associated with ASD risk across all ASD sub-groups. Results suggest differences in ASD etiology by comorbid subgroups and highlight potential modifiable risk factors.

Mandible is a bony structure of neuroectodermal origin with unique characteristics that support dentition and jaw movements. In the present study, we investigated the effects of gestational exposure to a mixture of endocrine-disrupting chemicals (EDCs) on mandibular growth in mice. The mixture under study (Mixture N1) has been associated with neurodevelopmental effects in both a human cohort and animal studies. Pregnant mice were exposed throughout gestation to 0.5x (times of pregnant women's exposure levels), 10x, 100x and 500x of Mixture N1, or the vehicle, and the mandibles of the male offspring were studied in adulthood. Micro-CT analysis showed non-monotonic effects of Mixture N1 in the distances between specific mandibular landmarks and in the crown width of M1 molar, as well as changes in the mandibular bone characteristics. The alveolar bone volume was reduced, and the trabecular separation was increased in the 500x exposed mice. Bone volume in the condyle head was increased in all treated groups. Tau he Safranin-O-stained area of mature hypertrophic chondrocytes and the width of their zones were reduced in 0.5x, 10x and 100x exposed groups. This is the first indication that prenatal exposure to an epidemiologically defined EDC mixture, associated with neurodevelopmental impacts, can also affect mandibular growth in mammals.

BackgroundEndocrine disrupting chemicals (EDCs) can cross the placenta and thereby expose the fetus, which may lead to developmental consequences. It is still unclear which chemicals are of concern regarding neurodevelopment and specifically behaviour, when being exposed to a mixture.ObjectiveThe objective is to determine associations between prenatal exposure to EDCs and behavioural difficulties. Furthermore, we investigated sex-specific associations and determined chemicals of concern in significant regressions.MethodsAssociations between prenatal exposure to EDCs (both as single compounds and their mixtures) and behavioural outcomes using the Strengths and Difficulties Questionnaire (SDQ) were estimated in 607 mother-child pairs in the Swedish Environmental Longitudinal, Mother and Child, Asthma and Allergy (SELMA) study. Levels for chemical compounds were measured in either urine or serum (median of 10 weeks of gestation). Associations were estimated for the total SDQ score (quasipoisson regression) and a 90th percentile cut-off (logistic regression). Exposure for EDC mixtures (phenols, phthalates, PFAS and persistent chlorinated) was studied using weighted quantile sum (WQS) regression with deciles and with and without repeated holdout validation techniques. The models were adjusted for selected covariates.ResultsThe odds for behavioural difficulties increased in girls with higher chemical exposures (OR 1.77, 95% CI 1.67, 1.87) using the full sample and borderline for the validation set (OR 1.31, 95% CI 0.93, 1.85) with 94/100 positive betas in the 100 repeated holdout validations. Chemicals of concern for girls are mostly short-lived chemicals and more specifically plasticizers. No pattern of significant associations was detected for boys.SignificanceThere is an indication of increased behavioural difficulties for girls in the SELMA population with higher exposure to mixtures of EDCs. Using the repeated holdout validation techniques, the inference is more stable, reproducible and generalisable. Prenatal exposure to mixtures of environmental chemicals should be considered when assessing the safety of chemicals.ImpactGrowing evidence points towards a "mixture effect" where different environmental chemicals might act jointly where individual compounds may be below a level of concern, but the combination may have an effect on human health. We are constantly exposed to a complicated mixture pattern that is individual for every person as this mixture depends on personal choices of lifestyle, diet and housing to name a few. Our study suggests that prenatal exposure to EDCs might adversely affect the behaviour of children and especially girls. Hence, risk assessment needs to improve and sex-specific mechanisms should be included in assessments.

The CHemical Exposure and Children’s Health (CHECH) study is an ongoing pregnancy cohort study in Tianjin, China. This paper describes the background, aim and the study design, which can be followed by future researchers to design and conduct similar studies. The abundance and the potential adverse health outcomes of endocrine disrupting chemicals (EDCs) is concerning. More notably, developing fetuses and infants are more vulnerable to EDCs exposure. The CHECH study aims to investigate the importance of early life exposure to multiple EDCs (phthalates and their metabolites, bisphenol A and their substitutes, perfluorinated compounds and poly brominated diphenyl ethers) for multiple health outcomes in Chinese children, namely sexual development, neurodevelopment, metabolism and growth, as well as asthma and allergy. A total of 2238 pregnant women were recruited in Tianjin from May 2017 to April 2021 with a response rate of 90 %. Among these women, 2255 children were born with available information, including 47 pairs of twins. Urine samples were collected from pregnant women and children, while air and dust samples were obtained from the home environment during pregnancy and infancy periods. Information on children’s health was gathered through physical examinations and questionnaires. The CHECH study, which collected exposure information and health outcomes at multiple time points, will contribute to the understanding of prenatal exposure to EDCs and their impact on children’s health, thereby facilitating the development of risk assessments aimed at reducing exposure and associated health risks.