Rethinking the idea of late autism spectrum disorder onset

Prenatal Exposure to Source-Specific Fine Particulate Matter and Autism Spectrum Disorder

In this study, associations between prenatal exposure to fine particulate matter (PM2.5) from 9 sources and development of autism spectrum disorder (ASD) were assessed in a population-based retrospective pregnancy cohort in southern California. The cohort included 318,750 mother-child singleton pairs. ASD cases (N = 4559) were identified by ICD codes. Source-specific PM2.5 concentrations were estimated from a chemical transport model with a 4 × 4 km2 resolution and assigned to maternal pregnancy residential addresses. Cox proportional hazard models were used to estimate the hazard ratios (HR) of ASD development for each individual source. We also adjusted for total PM2.5 mass and in a separate model for all other sources simultaneously. Increased ASD risk was observed with on-road gasoline (HR [CI]: 1.18 [1.13, 1.24]), off-road gasoline (1.15 [1.12, 1.19]), off-road diesel (1.08 [1.05, 1.10]), food cooking (1.05 [1.02, 1.08]), aircraft (1.04 [1.01, 1.06]), and natural gas combustion (1.09 [1.06, 1.11]), each scaled to standard deviation increases in concentration. On-road gasoline and off-road gasoline were robust for other pollutant groups. PM2.5 emitted from different sources may have different impacts on ASD. The results also identify PM source mixtures for toxicological investigations that may provide evidence for future public health policies.

Is autism a PIN1 deficiency syndrome? A proposed etiological role for glyphosate

Autism is a neurodevelopmental disorder, the prevalence of which has increased dramatically in the United States over the past two decades. It is characterized by stereotyped behaviors and impairments in social interaction and communication. In this paper, we present evidence that autism can be viewed as a PIN1 deficiency syndrome. Peptidyl-prolyl cis/trans isomerase, NIMA-Interacting 1 (PIN1) is a peptidyl-prolyl cis/trans isomerase, and it has widespread influences in biological organisms. Broadly speaking, PIN1 deficiency is linked to many neurodegenerative diseases, whereas PIN1 over-expression is linked to cancer. Death-associated protein kinase 1 (DAPK1) strongly inhibits PIN1, and the hormone melatonin inhibits DAPK1. Melatonin deficiency is strongly linked to autism. It has recently been shown that glyphosate exposure to rats inhibits melatonin synthesis as a result of increased glutamate release from glial cells and increased expression of metabotropic glutamate receptors. Glyphosate's inhibition of melatonin leads to a reduction in PIN1 availability in neurons. In this paper, we show that PIN1 deficiency can explain many of the unique morphological features of autism, including increased dendritic spine density, missing or thin corpus callosum, and reduced bone density. We show how PIN1 deficiency disrupts the functioning of powerful high-level signaling molecules, such as nuclear factor erythroid 2-related factor 2 (NRF2) and p53. Dysregulation of both of these proteins has been linked to autism. Severe depletion of glutathione in the brain resulting from chronic exposure to oxidative stressors and extracellular glutamate leads to oxidation of the cysteine residue in PIN1, inactivating the protein and further contributing to PIN1 deficiency. Impaired autophagy leads to increased sensitivity of neurons to ferroptosis. It is imperative that further research be conducted to experimentally validate whether the mechanisms described here take place in response to chronic glyphosate exposure and whether this ultimately leads to autism.

Screening accuracy and cut-offs of the Polish version of Communication and Symbolic Behavior Scales-Developmental Profile Infant-Toddler Checklist

BACKGROUND

The first stage of diagnosing autism spectrum disorders usually involves population screening to detect children at risk. This study aims to assess the predictive convergent validity of the Polish version of the Communication and Symbolic Behavior Scales-Developmental Profile Infant-Toddler Checklist (CSBS-DP ITC) with the Autism Spectrum Rating Scales (ASRS), evaluate its sensitivity and specificity and assess the cut-off points for the possibility of using this questionnaire in population screening among children aged 6 to 24 months.

METHOD

The study was conducted among 602 children from the general population who had previously participated in the earlier phase of validation of the questionnaire for Polish conditions. The collected data were statistically processed to calculate the accuracy (i.e. sensitivity, specificity) of the questionnaire.

RESULTS

In individual age groups, the sensitivity of the questionnaire varies from 0.667 to 0.750, specificity from 0.854 to 0.939, positive predictive value from 0.261 to 0.4 and negative predictive value-from 0.979 to 0.981. Screening accuracy ranges from 0.847 to 0.923 depending on the age group. The adopted cut-off points are 21 points for children aged 9-12 months, 36 for children aged 13-18 months, 39 for children aged 19-24 months. Cut-off points could not be established for children aged 6-8 months. The convergent validity values with the ASRS ranged from -0.28 to -0.431 and were highest in the group of the oldest children.

CONCLUSIONS

These results indicate that the Polish version of the CSBS-DP ITC can be used as an effective tool for ASD universal screening.

Maternal Thyroid Dysfunction During Pregnancy as an Etiologic Factor in Autism Spectrum Disorder: Challenges and Opportunities for Research

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition with unknown etiology. Both genetic and environmental factors have been associated with ASD. Environmental exposures during the prenatal period may play an important role in ASD development. This narrative review critically examines the evidence for a relationship between maternal thyroid dysfunction during pregnancy and ASD in the child. Summary: Studies that assessed the associations of hypothyroidism, hyperthyroidism, hypothyroxinemia, thyroid hormone concentrations, or autoimmune thyroid disease with ASD outcomes were included. Most research focused on the relationship between hypothyroidism and ASD. Multiple population-based studies found that maternal hypothyroidism was associated with higher likelihood of an ASD diagnosis in offspring. Associations with other forms of maternal thyroid dysfunction were less consistent. Findings may have been affected by misclassification bias, survival bias, or publication bias. Studies using medical records may have misclassified subclinical thyroid dysfunction as euthyroidism. Two studies that assessed children at early ages may have misclassified those with ASD as typically developing. Most studies adjusted for maternal body mass index (BMI) and/or mental illness, but not interpregnancy interval or pesticide exposure, all factors associated with fetal survival and ASD. Most studies reported a combination of null and statistically significant findings, although publication bias is still possible. Conclusions: Overall, evidence supported a positive association between maternal thyroid dysfunction during pregnancy and ASD outcomes in the child, especially for hypothyroidism. Future studies could reduce misclassification bias by using laboratory measures instead of medical records to ascertain thyroid dysfunction and evaluating children for ASD at an age when it can be reliably detected. Survival bias could be further mitigated by adjusting models for more factors associated with fetal survival and ASD. Additional research is needed to comprehensively understand the roles of maternal levothyroxine treatment, iodine deficiency, or exposure to thyroid-disrupting compounds in the relationship between maternal thyroid dysfunction and child ASD outcomes.

Prenatal air pollution, maternal immune activation, and autism spectrum disorder

BACKGROUND

Autism Spectrum Disorder (ASD) risk is highly heritable, with potential additional non-genetic factors, such as prenatal exposure to ambient particulate matter with aerodynamic diameter < 2.5 µm (PM2.5) and maternal immune activation (MIA) conditions. Because these exposures may share common biological effect pathways, we hypothesized that synergistic associations of prenatal air pollution and MIA-related conditions would increase ASD risk in children.

OBJECTIVES

This study examined interactions between MIA-related conditions and prenatal PM2.5 or major PM2.5 components on ASD risk.

METHODS

In a population-based pregnancy cohort of children born between 2001 and 2014 in Southern California, 318,751 mother-child pairs were followed through electronic medical records (EMR); 4,559 children were diagnosed with ASD before age 5. Four broad categories of MIA-related conditions were classified, including infection, hypertension, maternal asthma, and autoimmune conditions. Average exposures to PM2.5 and four PM2.5 components, black carbon (BC), organic matter (OM), nitrate (NO3-), and sulfate (SO42-), were estimated at maternal residential addresses during pregnancy. We estimated the ASD risk associated with MIA-related conditions, air pollution, and their interactions, using Cox regression models to adjust for covariates.

RESULTS

ASD risk was associated with MIA-related conditions [infection (hazard ratio 1.11; 95% confidence interval 1.05-1.18), hypertension (1.30; 1.19-1.42), maternal asthma (1.22; 1.08-1.38), autoimmune disease (1.19; 1.09-1.30)], with higher pregnancy PM2.5 [1.07; 1.03-1.12 per interquartile (3.73 μg/m3) increase] and with all four PM2.5 components. However, there were no interactions of each category of MIA-related conditions with PM2.5 or its components on either multiplicative or additive scales.

CONCLUSIONS

MIA-related conditions and pregnancy PM2.5 were independently associations with ASD risk. There were no statistically significant interactions of MIA conditions and prenatal PM2.5 exposure with ASD risk.

A predictive ensemble classifier for the gene expression diagnosis of ASD at ages 1 to 4 years

Autism Spectrum Disorder (ASD) diagnosis remains behavior-based and the median age of diagnosis is ~52 months, nearly 5 years after its first-trimester origin. Accurate and clinically-translatable early-age diagnostics do not exist due to ASD genetic and clinical heterogeneity. Here we collected clinical, diagnostic, and leukocyte RNA data from 240 ASD and typically developing (TD) toddlers (175 toddlers for training and 65 for test). To identify gene expression ASD diagnostic classifiers, we developed 42,840 models composed of 3570 gene expression feature selection sets and 12 classification methods. We found that 742 models had AUC-ROC ≥ 0.8 on both Training and Test sets. Weighted Bayesian model averaging of these 742 models yielded an ensemble classifier model with accurate performance in Training and Test gene expression datasets with ASD diagnostic classification AUC-ROC scores of 85-89% and AUC-PR scores of 84-92%. ASD toddlers with ensemble scores above and below the overall ASD ensemble mean of 0.723 (on a scale of 0 to 1) had similar diagnostic and psychometric scores, but those below this ASD ensemble mean had more prenatal risk events than TD toddlers. Ensemble model feature genes were involved in cell cycle, inflammation/immune response, transcriptional gene regulation, cytokine response, and PI3K-AKT, RAS and Wnt signaling pathways. We additionally collected targeted DNA sequencing smMIPs data on a subset of ASD risk genes from 217 of the 240 ASD and TD toddlers. This DNA sequencing found about the same percentage of SFARI Level 1 and 2 ASD risk gene mutations in TD (12 of 105) as in ASD (13 of 112) toddlers, and classification based only on the presence of mutation in these risk genes performed at a chance level of 49%. By contrast, the leukocyte ensemble gene expression classifier correctly diagnostically classified 88% of TD and ASD toddlers with ASD risk gene mutations. Our ensemble ASD gene expression classifier is diagnostically predictive and replicable across different toddler ages, races, and ethnicities; out-performs a risk gene mutation classifier; and has potential for clinical translation.

Overall prognosis of preschool autism spectrum disorder diagnoses

BACKGROUND

Autism spectrum disorder is a neurodevelopmental disorder characterised by social communication difficulties, restricted interests and repetitive behaviours. The clinical pathway for children with a diagnosis of autism spectrum disorder is varied, and current research suggests some children may not continue to meet diagnostic criteria over time.

OBJECTIVES

The primary objective of this review was to synthesise the available evidence on the proportion of preschool children who have a diagnosis of autism spectrum disorder at baseline (diagnosed before six years of age) who continue to meet diagnostic criteria at follow-up one or more years later (up to 19 years of age).

SEARCH METHODS

We searched MEDLINE, Embase, PsycINFO, and eight other databases in October 2017 and ran top-up searches up to July 2021. We also searched reference lists of relevant systematic reviews.

SELECTION CRITERIA

Two review authors independently assessed prospective and retrospective follow-up studies that used the same measure and process within studies to diagnose autism spectrum disorder at baseline and follow-up. Studies were required to have at least one year of follow-up and contain at least 10 participants. Participants were all aged less than six years at baseline assessment and followed up before 19 years of age.

DATA COLLECTION AND ANALYSIS

We extracted data on study characteristics and the proportion of children diagnosed with autism spectrum disorder at baseline and follow-up. We also collected information on change in scores on measures that assess the dimensions of autism spectrum disorder (i.e. social communication and restricted interests and repetitive behaviours). Two review authors independently extracted data on study characteristics and assessed risk of bias using a modified quality in prognosis studies (QUIPS) tool. We conducted a random-effects meta-analysis or narrative synthesis, depending on the type of data available. We also conducted prognostic factor analyses to explore factors that may predict diagnostic outcome.

MAIN RESULTS

In total, 49 studies met our inclusion criteria and 42 of these (11,740 participants) had data that could be extracted. Of the 42 studies, 25 (60%) were conducted in North America, 13 (31%) were conducted in Europe and the UK, and four (10%) in Asia. Most (52%) studies were published before 2014. The mean age of the participants was 3.19 years (range 1.13 to 5.0 years) at baseline and 6.12 years (range 3.0 to 12.14 years) at follow-up. The mean length of follow-up was 2.86 years (range 1.0 to 12.41 years). The majority of the children were boys (81%), and just over half (60%) of the studies primarily included participants with intellectual disability (intelligence quotient < 70). The mean sample size was 272 (range 10 to 8564). Sixty-nine per cent of studies used one diagnostic assessment tool, 24% used two tools and 7% used three or more tools. Diagnosis was decided by a multidisciplinary team in 41% of studies. No data were available for the outcomes of social communication and restricted and repetitive behaviours and interests. Of the 42 studies with available data, we were able to synthesise data from 34 studies (69% of all included studies; n = 11,129) in a meta-analysis. In summary, 92% (95% confidence interval 89% to 95%) of participants continued to meet diagnostic criteria for autism spectrum disorder from baseline to follow-up one or more years later; however, the quality of the evidence was judged as low due to study limitations and inconsistency. The majority of the included studies (95%) were rated at high risk of bias. We were unable to explore the outcomes of change in social communication and restricted and repetitive behaviour and interests between baseline and follow-up as none of the included studies provided separate domain scores at baseline and follow-up. Details on conflict of interest were reported in 24 studies. Funding support was reported by 30 studies, 12 studies omitted details on funding sources and two studies reported no funding support. Declared funding sources were categorised as government, university or non-government organisation or charity groups. We considered it unlikely funding sources would have significantly influenced the outcomes, given the nature of prognosis studies.

AUTHORS' CONCLUSIONS

Overall, we found that nine out of 10 children who were diagnosed with autism spectrum disorder before six years of age continued to meet diagnostic criteria for autism spectrum disorder a year or more later, however the evidence was uncertain. Confidence in the evidence was rated low using GRADE, due to heterogeneity and risk of bias, and there were few studies that included children diagnosed using a current classification system, such as the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) or the eleventh revision of the International Classification of Diseases (ICD-11). Future studies that are well-designed, prospective and specifically assess prognosis of autism spectrum disorder diagnoses are needed. These studies should also include contemporary diagnostic assessment methods across a broad range of participants and investigate a range of relevant prognostic factors.

Maternal antibiotics disrupt microbiome, behavior, and temperature regulation in unexposed infant mice

Maternal antibiotic (ABx) exposure can significantly perturb the transfer of microbiota from mother to offspring, resulting in dysbiosis of potential relevance to neurodevelopmental disorders such as autism spectrum disorder (ASD). Studies in rodent models have found long-term neurobehavioral effects in offspring of ABx-treated dams, but ASD-relevant behavior during the early preweaning period has thus far been neglected. Here, we exposed C57BL/6J mouse dams to ABx (5 mg/ml neomycin, 1.25 μg/ml pimaricin, .075% v/v acetic acid) dissolved in drinking water from gestational day 12 through offspring postnatal day 14. A number of ASD-relevant behaviors were assayed in offspring, including ultrasonic vocalization (USV) production during maternal separation, group huddling in response to cold challenge, and olfactory-guided home orientation. In addition, we obtained measures of thermoregulatory competence in pups during and following behavioral testing. We found a number of behavioral differences in offspring of ABx-treated dams (e.g., modulation of USVs by pup weight, activity while huddling) and provide evidence that some of these behavioral effects can be related to thermoregulatory deficiencies, particularly at younger ages. Our results suggest not only that ABx can disrupt microbiomes, thermoregulation, and behavior, but that metabolic effects may confound the interpretation of behavioral differences observed after early-life ABx exposure.

Evidence of susceptibility to autism risks associated with early life ambient air pollution: A systematic review

BACKGROUND

Many studies have found associations between early life air pollution exposure and subsequent onset of autism spectrum disorder (ASD). However, characteristics that affect susceptibility remain unclear.

OBJECTIVE

This systematic review examined epidemiologic studies on the modifying roles of social, child, genetic and maternal characteristics in associations between prenatal and early postnatal air pollution exposure and ASD.

METHODS

A systematic literature search in PubMed and Embase was conducted. Studies that examined modifiers of the association between air pollution and ASD were included.

RESULTS

A total of 19 publications examined modifiers of the associations between early life air pollution exposures and ASD. In general, estimates of effects on risk of ASD in boys were larger than in girls (based on 11 studies). Results from studies of effects of family education (2 studies) and neighborhood deprivation (2 studies) on air pollution-ASD associations were inconsistent. Limited data (1 study) suggest pregnant women with insufficient folic acid intake might be more susceptible to ambient particulate matter less than 2.5 μm (PM2.5) and 10 μm (PM10) in aerodynamic diameter, and to nitrogen dioxide (NO2). Children of mothers with gestational diabetes had increased risk of ozone-associated ASD (1 study). Two genetic studies reported that copy number variations may amplify the effect of ozone, and MET rs1858830 CC genotype may augment effects of PM and near-roadway pollutants on ASD.

CONCLUSIONS

Child's sex, maternal nutrition or diabetes, socioeconomic factors, and child risk genotypes were reported to modify the effect of early-life air pollutants on ASD risk in the epidemiologic literature. However, the sparsity of studies on comparable modifying hypotheses precludes conclusive findings. Further research is needed to identify susceptible populations and potential targets for preventive intervention.

Neural responses to affective speech, including motherese, map onto clinical and social eye tracking profiles in toddlers with ASD

Affective speech, including motherese, captures an infant's attention and enhances social, language and emotional development. Decreased behavioural response to affective speech and reduced caregiver-child interactions are early signs of autism in infants. To understand this, we measured neural responses to mild affect speech, moderate affect speech and motherese using natural sleep functional magnetic resonance imaging and behavioural preference for motherese using eye tracking in typically developing toddlers and those with autism. By combining diverse neural-clinical data using similarity network fusion, we discovered four distinct clusters of toddlers. The autism cluster with the weakest superior temporal responses to affective speech and very poor social and language abilities had reduced behavioural preference for motherese, while the typically developing cluster with the strongest superior temporal response to affective speech showed the opposite effect. We conclude that significantly reduced behavioural preference for motherese in autism is related to impaired development of temporal cortical systems that normally respond to parental affective speech.

The Early Screening for Autism and Communication Disorders: Field-testing an autism-specific screening tool for children 12 to 36 months of age

LAY ABSTRACT

There is a critical need for accurate screening tools for autism spectrum disorder in very young children so families can access tailored intervention services as early as possible. However, there are few screeners designed for children 18-24 months. Developing screeners that pick up on the signs of autism spectrum disorder in very young children has proved even more challenging. In this study, we examined a new autism-specific parent-report screening tool, the Early Screening for Autism and Communication Disorders for children between 12 and 36 months of age. Field-testing was done in five sites with 471 children screened for communication delays in primary care or referred for familial risk or concern for autism spectrum disorder. The Early Screening for Autism and Communication Disorders was tested in three age groups: 12-17, 18-23, and 24-36 months. A best-estimate diagnosis of autism spectrum disorder, developmental delay, or typical development was made. Analyses examined all 46 items and identified 30 items that best discriminated autism spectrum disorder from the non-spectrum groups. Cutoffs were established for each age group with good sensitivity and specificity. Results provide preliminary support for the accuracy of the Early Screening for Autism and Communication Disorders as an autism-specific screener in children 12-36 months with elevated risk of communication delay or autism spectrum disorder.

Get SET Early to Identify and Treatment Refer Autism Spectrum Disorder at 1 Year and Discover Factors That Influence Early Diagnosis

OBJECTIVES

To examine the impact of a new approach, Get SET Early, on the rates of early autism spectrum disorder (ASD) detection and factors that influence the screen-evaluate-treat chain.

STUDY DESIGN

After attending Get SET Early training, 203 pediatricians administered 57 603 total screens using the Communication and Symbolic Behavior Scales Infant-Toddler Checklist at 12-, 18-, and 24-month well-baby examinations, and parents designated presence or absence of concern. For screen-positive toddlers, pediatricians specified if the child was being referred for evaluation, and if not, why not.

RESULTS

Collapsed across ages, toddlers were evaluated and referred for treatment at a median age of 19 months, and those screened at 12 months (59.4% of sample) by 15 months. Pediatricians referred one-third of screen-positive toddlers for evaluation, citing lack of confidence in the accuracy of screen-positive results as the primary reason for nonreferral. If a parent expressed concerns, referral probability doubled, and the rate of an ASD diagnosis increased by 37%. Of 897 toddlers evaluated, almost one-half were diagnosed as ASD, translating into an ASD prevalence of 1%.

CONCLUSIONS

The Get SET Early model was effective at detecting ASD and initiating very early treatment. Results also underscored the need for change in early identification approaches to formally operationalize and incorporate pediatrician judgment and level of parent concern into the process.

Early and Repeated Screening Detects Autism Spectrum Disorder

OBJECTIVE

To evaluate timing and accuracy of early and repeated screening for autism spectrum disorder (ASD) during well-child visits.

STUDY DESIGN

Using a longitudinal study design, toddlers (n = 5784) were initially screened at 12 (n = 1504), 15 (n = 1228), or 18 (n = 3052) months during well-child visits, and rescreened at 18, 24, and 36 months. Of those screened, 368 toddlers attended an ASD evaluation after a positive screen and/or a provider concern for ASD at any visit.

RESULTS

Screens initiated at 12 months yielded an ASD diagnosis significantly earlier than at 15 months (P = .003, d = 0.99) and 18 months (P < .001, d = 0.97). Cross-group overall sensitivity of the initial screen was .715 and specificity was .959. Repeat screening improves sensitivity (82.1%), without notably decreasing specificity (all >93.5%). Screening at 18 months resulted in significantly higher positive predictive value than at 12 months (X² (1, n = 221) = 9.87, P = .002, OR = 2.60) and 15 months (X² (1, n = 208) = 14.57, P < .001, OR = 3.67). With repeat screening, positive predictive value increased for all screen groups, but the increase was not significant.

CONCLUSIONS

Screening as early as 12 months effectively identifies many children at risk for ASD. Children screened at 12 months receive a diagnosis of ASD significantly earlier than peers who are first screened at later ages, facilitating earlier intervention. However, as the sensitivity is lower for a single screen, screening needs to be repeated.

Validation of the Modified Checklist for Autism in Toddlers, Revised with Follow-up in a Population Sample of 30-Month-Old Children in Iceland: A Prospective Approach

The Modified Checklist for Autism in Toddlers, Revised with Follow-up was validated on a population sample in Reykjavik, Iceland. The participants (N = 1585) were screened in well-child care at age 30 months and followed up for at least 2 years to identify autism cases. The sensitivity, specificity, positive and negative predictive values were 0.62, 0.99, 0.72, and 0.99, respectively. True-positive children were diagnosed 10 months earlier than false-negative children. Autism symptom severity and the proportions of children with verbal and performance IQs/DQs < 70 were similar between groups. Although the sensitivity was suboptimal, the screening contributed to lowering the age at diagnosis for many children. Adding autism-specific screening to the well-child care program should be considered.

Prenatal exposure to bisphenol A and autistic- and ADHD-related symptoms in children aged 2 and5 years from the Odense Child Cohort

BACKGROUND

Bisphenol A (BPA) is a non-persistent chemical with endocrine disrupting abilities used in a variety of consumer products. Fetal exposure to BPA is of concern due to the elevated sensitivity, which particularly relates to the developing brain. Several epidemiological studies have investigated the association between prenatal BPA exposure and neurodevelopment, but the results have been inconclusive.

OBJECTIVE

To assess the association between in utero exposure to BPA and Attention Deficit/Hyperactivity Disorder (ADHD-) symptoms and symptoms of Autism Spectrum Disorder (ASD) in 2 and 5-year old Danish children.

METHOD

In the prospective Odense Child Cohort, BPA was measured in urine samples collected in gestational week 28 and adjusted for osmolality. ADHD and ASD symptoms were assessed with the use of the ADHD scale and ASD scale, respectively, derived from the Child Behaviour Checklist preschool version (CBCL/1½-5) at ages 2 and 5 years. Negative binomial and multiple logistic regression analyses were performed to investigate the association between maternal BPA exposure (continuous ln-transformed or divided into tertiles) and the relative differences in ADHD and ASD problem scores and the odds (OR) of an ADHD and autism score above the 75th percentile adjusting for maternal educational level, maternal age, pre-pregnancy BMI, parity and child age at evaluation in 658 mother-child pairs at 2 years of age for ASD-score, and 427 mother-child pairs at 5 years of age for ADHD and ASD-score.

RESULTS

BPA was detected in 85.3% of maternal urine samples even though the exposure level was low (median 1.2 ng/mL). No associations between maternal BPA exposure and ASD at age 2 years or ADHD at age 5 years were found. Trends of elevated Odds Ratios (ORs) were seen among 5 year old children within the 3rd tertile of BPA exposure with an ASD-score above the 75th percentile (OR = 1.80, 95% CI 0.97,3.32), being stronger for girls (OR = 3.17, 95% CI 1.85,9.28). A dose-response relationship was observed between BPA exposure and ASD-score at 5 years of age (p-trend 0.06) in both boys and girls, but only significant in girls (p-trend 0.03).

CONCLUSION

Our findings suggest that prenatal BPA exposure even in low concentrations may increase the risk of ASD symptoms which may predict later social abilities. It is therefore important to follow-up these children at older ages, measure their own BPA exposure, and determine if the observed associations persist.

Prevalence and Age of Onset of Regression in Children with Autism Spectrum Disorder: A Systematic Review and Meta-analytical Update

A systematic review published in 2013 reported 32% of children on the autism spectrum experience skill loss, known as autistic regression. However, the frequency varied depending on definition and measures used to capture skills. Retrospective parent report and prospective observation indicate loss of language and/or social skills, with motor skills typically unaffected. Our aim was to update the prevalence and age of onset of autistic regression through a meta-analysis of the literature to understand if there have been changes to the reported onset and prevalence since 2010. A systematic literature search was conducted using Medline, Embase, PsycINFO, and the Cochrane Library databases and included studies published from 2010 onward. Risk of bias assessment was performed on included studies. A random effects model was used to calculate the pooled prevalence and age of onset of autistic regression. Ninety-seven studies were included in the systematic review, of which 75 studies involving 33,014 participants had sufficient data for meta-analytic syntheses. The pooled proportion of autistic regression was 30% (95% confidence interval [CI]: 27-32%) but heterogeneity was high (I² = 96.91) and did not reduce with sensitivity or subgroup analyses based on study design or clinical differences, respectively. Prevalence varied according to risk of bias (low: 27%) and definition of regression (language: 20%, language/social: 40%, mixed: 30%, and unspecified: 27%). Weighted average age of onset was 19.8 months. Findings from this meta-analysis highlight the importance of developing a standardized definition of autistic regression, and tools to measure this at multiple time points during early childhood development. LAY SUMMARY: About a third of children with Autism Spectrum Disorder experience loss of skills, which is also known as autistic regression. This paper provides an update of the rate of autistic regression in children and the age when they first experience loss of skills, based on current studies. The findings from this review contribute to our understanding of the onset patterns of autistic regression. Unfortunately, studies are not sufficiently similar, making it difficult to provide clear answers on the exact timing or type of regression seen in different children.

Factors Associated with a Delayed Autism Spectrum Disorder Diagnosis in Children Previously Assessed on Suspicion of Autism

This study aimed to investigate factors associated with a delayed autism spectrum (ASD) diagnosis when compared to children with either no or early ASD diagnosis. Among 893 children assessed for ASD before age 8, 39% had no ASD at baseline, of which 21% received a later ASD diagnosis. Autism symptoms, diagnostic history of other developmental disorders, cognitive ability, and socioeconomic factors were associated with delayed ASD. Autism Diagnostic Observation Schedule (ADOS) scores in delayed ASD fell between early and no ASD. Other developmental disorders, time and clinical trends like ADOS use and low parental education distinguished delayed and early ASD, whereas higher frequency of IQ < 70 at baseline and a diagnosis of emotional disorders during follow-up distinguished delayed and no ASD.

Uncovering neurodevelopmental paths to autism spectrum disorder through an integrated analysis of developmental measures and neural sensitivity to faces

BACKGROUND

Autism spectrum disorder (ASD) is highly heterogeneous in its etiology and manifestation. The neurobiological processes underlying ASD development are reflected in multiple features, from behaviour and cognition to brain functioning. An integrated analysis of these features may optimize the identification of these processes.

METHODS

We examined cognitive and adaptive functioning and ASD symptoms between 8 and 36 months in 161 infants at familial high risk for ASD and 71 low-risk controls; we also examined neural sensitivity to eye gaze at 8 months in a subsample of 140 high-risk and 61 low-risk infants. We used linked independent component analysis to extract patterns of variation across domains and development, and we selected the patterns significantly associated with clinical classification at 36 months.

RESULTS

An early process at 8 months, indicating high levels of functioning and low levels of symptoms linked to higher attention to gaze shifts, was reduced in infants who developed ASD. A longitudinal process of increasing functioning and low levels of symptoms was reduced in infants who developed ASD, and another process suggesting a stagnation in cognitive functioning at 24 months was increased in infants who developed ASD.

LIMITATIONS

Although the results showed a clear significant trend relating to clinical classification, we found substantial overlap between groups.

CONCLUSION

We uncovered underlying processes that acted together early in development and were associated with clinical outcomes. Our results highlighted the complexity of emerging ASD, which goes beyond the borders of clinical categories. Future work should integrate genetic data to investigate the specific genetic risks linked to these processes.

Identifying prognostic markers in autism spectrum disorder using eye tracking

While many children with autism spectrum disorder are now detected at young ages given the rise in screening and general awareness, little is known regarding the prognosis of early detected children. The brain is shaped by experience-dependent mechanisms; thus, what a child pays attention to plays a pivotal role in shaping brain development. Eye tracking can provide an index of a child's visual attention and, as such, holds promise as a technology for revealing prognostic markers. In this, 49 children aged 1-3 years with autism spectrum disorder participated in an eye-tracking test, the GeoPref Test, that revealed preference for social versus nonsocial images. Next, children participated in a comprehensive test battery 5-9 years following the initial GeoPref Test. Statistical tests examined whether early age eye tracking predicted later school-age outcomes in symptom severity, social functioning, adaptive behavior, joint attention, and IQ. Results indicated that toddlers with higher preference for geometric images demonstrated greater symptom severity and fewer gaze shifts at school age. This relationship was not found in relation to IQ or adaptive behavior. Overall, the GeoPref Test holds promise as a symptom severity prognostic tool; further development of eye-tracking paradigms may enhance prognostic power and prove valuable in validating treatment progress.

Evaluation of the Diagnostic Stability of the Early Autism Spectrum Disorder Phenotype in the General Population Starting at 12 Months

IMPORTANCE

Universal early screening for autism spectrum disorder (ASD) in primary care is becoming increasingly common and is believed to be a pivotal step toward early treatment. However, the diagnostic stability of ASD in large cohorts from the general population, particularly in those younger than 18 months, is unknown. Changes in the phenotypic expression of ASD across early development compared with toddlers with other delays are also unknown.

OBJECTIVES

To examine the diagnostic stability of ASD in a large cohort of toddlers starting at 12 months of age and to compare this stability with that of toddlers with other disorders, such as developmental delay.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective cohort study performed from January 1, 2006, to December 31, 2018, a total of 2241 toddlers were referred from the general population through a universal screening program in primary care or community referral. Eligible toddlers received their first diagnostic evaluation between 12 and 36 months of age and had at least 1 subsequent evaluation.

EXPOSURES

Diagnosis was denoted after each evaluation visit as ASD, ASD features, language delay, developmental delay, other developmental issue, typical sibling of an ASD proband, or typical development.

MAIN OUTCOMES AND MEASURES

Diagnostic stability coefficients were calculated within 2-month age bands, and logistic regression models were used to explore the associations of sex, age, diagnosis at first visit, and interval between first and last diagnosis with stability. Toddlers with a non-ASD diagnosis at their first visit diagnosed with ASD at their last were designated as having late-identified ASD.

RESULTS

Among the 1269 toddlers included in the study (918 [72.3%] male; median age at first evaluation, 17.6 months [interquartile range, 14.0-24.4 months]; median age at final evaluation, 36.2 months [interquartile range, 33.4-40.9 months]), the overall diagnostic stability for ASD was 0.84 (95% CI, 0.80-0.87), which was higher than any other diagnostic group. Only 7 toddlers (1.8%) initially considered to have ASD transitioned into a final diagnosis of typical development. Diagnostic stability of ASD within the youngest age band (12-13 months) was lowest at 0.50 (95% CI, 0.32-0.69) but increased to 0.79 by 14 months and 0.83 by 16 months (age bands of 12 vs 14 and 16 months; odds ratio, 4.25; 95% CI, 1.59-11.74). A total of 105 toddlers (23.8%) were not designated as having ASD at their first visit but were identified at a later visit.

CONCLUSIONS AND RELEVANCE

The findings suggest that an ASD diagnosis becomes stable starting at 14 months of age and overall is more stable than other diagnostic categories, including language or developmental delay. After a toddler is identified as having ASD, there may be a low chance that he or she will test within typical levels at 3 years of age. This finding opens the opportunity to test the impact of very early-age treatment of ASD.

The Protracted Maturation of Associative Layer IIIC Pyramidal Neurons in the Human Prefrontal Cortex During Childhood: A Major Role in Cognitive Development and Selective Alteration in Autism

The human specific cognitive shift starts around the age of 2 years with the onset of self-awareness, and continues with extraordinary increase in cognitive capacities during early childhood. Diffuse changes in functional connectivity in children aged 2-6 years indicate an increase in the capacity of cortical network. Interestingly, structural network complexity does not increase during this time and, thus, it is likely to be induced by selective maturation of a specific neuronal subclass. Here, we provide an overview of a subclass of cortico-cortical neurons, the associative layer IIIC pyramids of the human prefrontal cortex. Their local axonal collaterals are in control of the prefrontal cortico-cortical output, while their long projections modulate inter-areal processing. In this way, layer IIIC pyramids are the major integrative element of cortical processing, and changes in their connectivity patterns will affect global cortical functioning. Layer IIIC neurons have a unique pattern of dendritic maturation. In contrast to other classes of principal neurons, they undergo an additional phase of extensive dendritic growth during early childhood, and show characteristic molecular changes. Taken together, circuits associated with layer IIIC neurons have the most protracted period of developmental plasticity. This unique feature is advanced but also provides a window of opportunity for pathological events to disrupt normal formation of cognitive circuits involving layer IIIC neurons. In this manuscript, we discuss how disrupted dendritic and axonal maturation of layer IIIC neurons may lead into global cortical disconnectivity, affecting development of complex communication and social abilities. We also propose a model that developmentally dictated incorporation of layer IIIC neurons into maturing cortico-cortical circuits between 2 to 6 years will reveal a previous (perinatal) lesion affecting other classes of principal neurons. This "disclosure" of pre-existing functionally silent lesions of other neuronal classes induced by development of layer IIIC associative neurons, or their direct alteration, could be found in different forms of autism spectrum disorders. Understanding the gene-environment interaction in shaping cognitive microcircuitries may be fundamental for developing rehabilitation and prevention strategies in autism spectrum and other cognitive disorders.

The ASD Living Biology: from cell proliferation to clinical phenotype

Autism spectrum disorder (ASD) has captured the attention of scientists, clinicians and the lay public because of its uncertain origins and striking and unexplained clinical heterogeneity. Here we review genetic, genomic, cellular, postmortem, animal model, and cell model evidence that shows ASD begins in the womb. This evidence leads to a new theory that ASD is a multistage, progressive disorder of brain development, spanning nearly all of prenatal life. ASD can begin as early as the 1st and 2nd trimester with disruption of cell proliferation and differentiation. It continues with disruption of neural migration, laminar disorganization, altered neuron maturation and neurite outgrowth, disruption of synaptogenesis and reduced neural network functioning. Among the most commonly reported high-confidence ASD (hcASD) genes, 94% express during prenatal life and affect these fetal processes in neocortex, amygdala, hippocampus, striatum and cerebellum. A majority of hcASD genes are pleiotropic, and affect proliferation/differentiation and/or synapse development. Proliferation and subsequent fetal stages can also be disrupted by maternal immune activation in the 1st trimester. Commonly implicated pathways, PI3K/AKT and RAS/ERK, are also pleiotropic and affect multiple fetal processes from proliferation through synapse and neural functional development. In different ASD individuals, variation in how and when these pleiotropic pathways are dysregulated, will lead to different, even opposing effects, producing prenatal as well as later neural and clinical heterogeneity. Thus, the pathogenesis of ASD is not set at one point in time and does not reside in one process, but rather is a cascade of prenatal pathogenic processes in the vast majority of ASD toddlers. Despite this new knowledge and theory that ASD biology begins in the womb, current research methods have not provided individualized information: What are the fetal processes and early-age molecular and cellular differences that underlie ASD in each individual child? Without such individualized knowledge, rapid advances in biological-based diagnostic, prognostic, and precision medicine treatments cannot occur. Missing, therefore, is what we call ASD Living Biology. This is a conceptual and paradigm shift towards a focus on the abnormal prenatal processes underlying ASD within each living individual. The concept emphasizes the specific need for foundational knowledge of a living child's development from abnormal prenatal beginnings to early clinical stages. The ASD Living Biology paradigm seeks this knowledge by linking genetic and in vitro prenatal molecular, cellular and neural measurements with in vivo post-natal molecular, neural and clinical presentation and progression in each ASD child. We review the first such study, which confirms the multistage fetal nature of ASD and provides the first in vitro fetal-stage explanation for in vivo early brain overgrowth. Within-child ASD Living Biology is a novel research concept we coin here that advocates the integration of in vitro prenatal and in vivo early post-natal information to generate individualized and group-level explanations, clinically useful prognoses, and precision medicine approaches that are truly beneficial for the individual infant and toddler with ASD.

What interests young autistic children? An exploratory study of object exploration and repetitive behavior

Behaviors characterized as restricted and repetitive (RRBs) in autism manifest in diverse ways, from motor mannerisms to intense interests, and are diagnostically defined as interfering with functioning. A variety of early autism interventions target RRBs as preoccupying young autistic children to the detriment of exploration and learning opportunities. In an exploratory study, we developed a novel stimulating play situation including objects of potential interest to autistic children, then investigated repetitive behaviors and object explorations in 49 autistic and 43 age-matched typical young children (20-69 months). Autistic children displayed significantly increased overall frequency and duration of repetitive behaviors, as well as increased specific repetitive behaviors. However, groups did not significantly differ in frequency and duration of overall object explorations, in number of different objects explored, or in explorations of specific objects. Exploratory analyses found similar or greater exploration of literacy-related objects in autistic compared to typical children. Correlations between repetitive behaviors and object explorations (their frequency and duration) revealed positive, not negative, associations in both groups. Our findings, from a novel situation incorporating potential autistic interests, suggest that RRBs do not necessarily displace exploration and its possibilities for learning in autism.

Parent-reported early symptoms of autism spectrum disorder in children without intellectual disability who were diagnosed at school age

Despite efforts to detect autism spectrum disorder during toddlerhood, many children with autism spectrum disorder remain undiagnosed until school age. To identify characteristics of children whose autism spectrum disorder might not be diagnosed during toddlerhood, this study used archived Autism Diagnostic Interview-Revised records to examine the historical presentation of autism spectrum disorder symptoms in 48 school-age children with autism spectrum disorder. Children diagnosed after starting school (Late-Diagnosed; n = 24) were compared to age-matched children diagnosed before school age (Early-Diagnosed; n = 24). Symptom presentation was similar between groups, with the Late-Diagnosed group exhibiting only marginally fewer symptoms historically. The most commonly reported historical symptoms were negative symptoms, namely, deficits in social behaviors. Positive symptoms, such as unusual preoccupations, rituals, and mannerisms, were less commonly reported. These findings may aid earlier identification of autism spectrum disorder in children who would likely be diagnosed at school age.

Naturalistic language sampling to characterize the language abilities of 3-year-olds with autism spectrum disorder

Characterization of language in naturalistic settings in autism spectrum disorder has been lacking, particularly at young ages, but such information is important for parents, teachers, and clinicians to better support language development in real-world settings. Factors contributing to this lack of clarity include conflicting definitions of language abilities, use of non-naturalistic standardized assessments, and restricted samples. The current study examined one of the largest datasets of naturalistic language samples in toddlers with autism spectrum disorder, and language delay and typically developing contrast groups at age 3. A range of indices including length of phrase, grammatical markings, and social use of language was assayed during a naturalistic observation of a parent-child play session. In contrast to historical estimates, results indicated only 3.7% of children with autism spectrum disorder used no words, and 34% were minimally verbal. Children with autism spectrum disorder and language delay exhibited similar usage of grammatical markings, although both were reduced compared to typically developing children. The greatest difference between autism spectrum disorder and language delay groups was the quantity of social language. Overall, findings highlight a range of language deficits in autism spectrum disorder, but also illustrate that the most severe level of impairments is not as common in naturalistic settings as previously estimated by standardized assessments.

Subplate neurons are the first cortical neurons to respond to sensory stimuli

In utero experience, such as maternal speech in humans, can shape later perception, although the underlying cortical substrate is unknown. In adult mammals, ascending thalamocortical projections target layer 4, and the onset of sensory responses in the cortex is thought to be dependent on the onset of thalamocortical transmission to layer 4 as well as the ear and eye opening. In developing animals, thalamic fibers do not target layer 4 but instead target subplate neurons deep in the developing white matter. We investigated if subplate neurons respond to sensory stimuli. Using electrophysiological recordings in young ferrets, we show that auditory cortex neurons respond to sound at very young ages, even before the opening of the ears. Single unit recordings showed that auditory responses emerged first in cortical subplate neurons. Subsequently, responses appeared in the future thalamocortical input layer 4, and sound-evoked spike latencies were longer in layer 4 than in subplate, consistent with the known relay of thalamic information to layer 4 by subplate neurons. Electrode array recordings show that early auditory responses demonstrate a nascent topographic organization, suggesting that topographic maps emerge before the onset of spiking responses in layer 4. Together our results show that sound-evoked activity and topographic organization of the cortex emerge earlier and in a different layer than previously thought. Thus, early sound experience can activate and potentially sculpt subplate circuits before permanent thalamocortical circuits to layer 4 are present, and disruption of this early sensory activity could be utilized for early diagnosis of developmental disorders.